An antioxidant jam and a method for preparing the same

Abstract

This invention belongs to the field of food processing technology and provides an antioxidant jam and its preparation method. The invention employs a synergistic design of a pectin-calcium ion microgel and a core-shell microcapsule bilayer microstructure. The core of the core-shell microcapsule contains ascorbic acid or sodium ascorbate, while the shell contains a pectin-calcium ion crosslinking network. This design helps to balance processing adaptability, structural stability, and preservation of antioxidant activity. It solves the technical challenges of the coupling contradiction between gel strength and water-free properties after the introduction of the ion-crosslinked microstructure, the synergistic optimization of microcapsule encapsulation efficiency and controllable release, and the thermosensitive degradation of ascorbic acid under heat treatment and shear conditions. This invention has broad application value in functional food fields such as jams, jellies, and baking fillings.

Description

Technical Field

[0001] This invention relates to the field of food processing technology, specifically to an antioxidant jam and its preparation method. Background Technology

[0002] Functional jams, as snack foods that combine nutritional value and sensory appeal, are increasingly widely used in the modern food industry, playing a significant role, especially in baking fillings, ready-to-eat breakfasts, and functional snacks. With consumers paying more attention to healthy functional ingredients, the market demand for jam products rich in antioxidant active ingredients continues to grow. Ascorbic acid, as a typical water-soluble antioxidant, possesses properties such as scavenging free radicals and delaying oxidation reactions. Its stable addition and long-term retention in jam systems are crucial for enhancing the nutritional value of products over their shelf life. However, ascorbic acid is highly susceptible to thermo-oxidative degradation during the high-temperature sterilization and shear dispersion processes in jam processing. Simultaneously, it faces a significant risk of chemical degradation in the high-sugar, high-acid storage environment of jams, leading to a rapid decline in the product's antioxidant activity over its shelf life. Achieving physical shielding and controlled release of ascorbic acid through microencapsulation technology, thereby improving its retention rate and storage stability under heat treatment conditions, has become a key technological path for the development of functional jams.

[0003] In recent years, pectin-based ion-crosslinked hydrogels have shown unique advantages in food encapsulation and sustained-release applications, but existing technologies still have significant shortcomings in jam systems. For example, Chinese patent application CN1252310A discloses a gel-enhancing formulation, but it suffers from problems such as excessively large gel particle size and easy breakage and failure under jam shear conditions. CN102553499B discloses a method for preparing and applying microcapsules based on low-ester pectin and calcium ion gelation, but it fails to resolve the contradiction between increased brittleness caused by excessive crosslinking of the gel network under high calcium ion concentration and structural stability due to water-free shrinkage. Existing technologies generally face three major technical bottlenecks: First, single-scale microstructures, when introduced into jam systems, cannot simultaneously meet the dual requirements of processing flowability and finished gel strength; second, there is a coupling contradiction between the encapsulation efficiency and sustained-release rate of core-shell microcapsules, with high encapsulation efficiency often accompanied by shell densification leading to release lag; third, during jam sterilization heat treatment and long-term storage, insufficient microcapsule structural stability leads to ascorbic acid leakage and degradation, making it difficult to achieve practical long-term retention rates. Summary of the Invention

[0004] The purpose of this invention is to provide an antioxidant jam and its preparation method, which solves the technical problems of the present invention, which is difficult to balance low viscosity processability with high solid content structural stability, gel strength with anti-water shelf stability, high encapsulation rate of microcapsules with controllable release after the introduction of ion-crosslinked microgels / microcapsules into jam systems, as well as the technical problems of ascorbic acid thermosensitive degradation under thermo-mechanical history conditions such as sterilization heat treatment and shear dispersion, which makes it difficult to simultaneously meet the requirements of antioxidant activity and long-term retention rate.

[0005] This invention employs a dual-level microstructure synergistic design concept, introducing a composite of nanoscale pectin-calcium ion microgels and micron-scale core-shell microcapsules into a jam matrix to achieve multi-level synergy between microstructure regulation and macroscopic performance optimization. The nanoscale microgels help improve the system's dispersibility and structural uniformity; the micron-scale microcapsules facilitate the encapsulation, protection, and release regulation of ascorbic acid. The differentiated design of the two phases in terms of particle size and spatial distribution allows the nano and micro phases to complement each other in the jam system, thus helping to balance processing adaptability, structural stability, and retention of antioxidant activity.

[0006] To achieve the above objectives, the present invention provides the following technical solution: An antioxidant jam, comprising the following components by weight: Fruit raw materials: 35.00-70.00 parts, wherein the fruit raw materials are in the form of one or more of the following: pre-processed fruit slices, fruit pieces, fruit pulp, and fruit puree; Sucrose 15.00-55.00 parts; Citric acid 0.05-0.80 parts; The total amount of calcium ions added is 0.02-0.25 parts, based on calcium ions. The sources of calcium ions include calcium ions introduced by intermediate A, calcium ions introduced by intermediate B, and / or calcium ions introduced by supplementary calcium salts. The supplementary calcium salts are selected from one or both of calcium chloride dihydrate and calcium lactate. When the supplementary calcium salt is calcium chloride dihydrate, the amount of calcium chloride dihydrate added does not exceed 0.10 parts, based on calcium chloride dihydrate. The actual amount of supplementary calcium salt added is used to achieve the total amount of calcium ions added and is not counted as an independent component in the total mass fraction of the above components. Intermediate A: 0.10-2.50 parts. The mass of intermediate A is based on dry solids, minus the equivalent mass of calcium ions contained therein. Pectin-calcium ion microgel is prepared by forming an ionic crosslinking network between pectin and calcium ions and then dispersing it by shearing. The pectin-calcium ion microgel is used in the form of a pectin-calcium ion microgel dispersion, or in the form of intermediate AP obtained after solid-liquid separation and drying. When intermediate A is used in the form of a pectin-calcium ion microgel dispersion, its actual addition amount is determined according to the measured solid content of the pectin-calcium ion microgel dispersion and the equivalent mass of calcium ions contained therein, so that the dry solids of intermediate A after deducting calcium ions reach the aforementioned mass. Intermediate B 0.05-5.00 parts, wherein the mass parts of intermediate B are based on dry solids and deduct the equivalent mass of calcium ions contained therein, wherein intermediate B is a core-shell microcapsule dispersion, wherein the core-shell microcapsule includes a core and a shell, wherein the core contains ascorbic acid or sodium ascorbate, and the shell contains an ionic crosslinking network formed by pectin and calcium ions, wherein when intermediate B is used in the form of a core-shell microcapsule dispersion, the actual amount added is determined based on the measured solid content of the core-shell microcapsule dispersion and the equivalent mass of calcium ions contained therein, so that the dry solids of intermediate B after deducting calcium ions reach the aforementioned mass parts; The remaining amount of deionized water ensures that the total mass of the above components is 100 parts, wherein the total amount of calcium ions added is the mass of calcium ions converted into parts by mass; the actual amount of calcium salts added is used to achieve the total amount of calcium ions added, and it is not counted again as an independent component in the total of 100 parts; wherein the mass of deionized water includes the water contained in intermediate A and / or intermediate B, including the water introduced when intermediate A and / or intermediate B are used in dispersion form, and the residual water of intermediate AP and / or intermediate BP, as well as the separately added deionized water; wherein the total mass of fruit raw materials and sucrose does not exceed 91.45 parts. The antioxidant jam has a pH value of 2.8-3.6.

[0007] Furthermore, the pectin-calcium ion microgel dispersion in intermediate A is prepared by forming an ionic cross-linking network between pectin and calcium ions under conditions of pH 3.2-4.2 and then dispersing it by shearing. The particle size of the microgel particles in the pectin-calcium ion microgel dispersion is 80-500 nm. The particle size is the Z-mean hydrated particle size measured by dynamic light scattering method. The dynamic light scattering method is used for determination at a test temperature of 25°C. The sample is diluted with deionized water to a solid content of 0.01-0.10 wt% before determination. The core-shell microcapsules in intermediate B have a particle size of 1-50 μm. The particle size is the median diameter D50 of the volume distribution measured by a laser particle size analyzer. The test temperature is 25℃. The sample is diluted with deionized water to a solid content of 0.1-1.0 wt% before measurement. Intermediate A is used in the form of a pectin-calcium ion microgel dispersion, or in the form of intermediate AP obtained by drying after solid-liquid separation; Intermediate B is used in the form of a core-shell microcapsule dispersion, or in the form of intermediate BP obtained by drying after solid-liquid separation.

[0008] Furthermore, the preparation method of intermediate A used in the antioxidant jam includes the following steps: A1. A pectin aqueous solution is prepared by adding low-methoxyl pectin to deionized water, wherein the pectin aqueous solution contains 0.50-2.00 wt% pectin and the degree of esterification of the low-methoxyl pectin is less than 50%; citric acid is added under stirring conditions, wherein the amount of citric acid added is 0.1-2.0 wt% of the dry weight of the pectin, and the pH value of the pectin aqueous solution is gradually adjusted to 3.2-4.2; A2, under normal pressure and at a temperature of 10-30℃, the pectin aqueous solution is sheared and dispersed at a rotation speed of 500-8000 rpm, while a calcium salt aqueous solution is added dropwise. The calcium salt aqueous solution is a deionized aqueous solution with a concentration of 10-50 mg / mL and is calculated as calcium ions. The dropping rate of the calcium salt aqueous solution is 0.5-10 mL / min. The mass ratio of the added calcium ions to the pectin is 0.02-0.15, where the mass of the pectin is the dry weight of the added pectin. The shearing and dispersion time is 5-30 min. A3, when the mass ratio of added calcium ions to the pectin reaches 0.02-0.15, stop adding the solution and continue shearing and dispersing for 3-15 minutes; A4. The obtained dispersion is filtered through a sieve with a pore size of 100-500 μm, and the filtrate is collected to obtain intermediate A; wherein the solid content of intermediate A is 0.60-2.50 wt%, and the particle size of the microgel particles is 80-500 nm.

[0009] Furthermore, the preparation method of intermediate B used in the antioxidant jam includes the following steps: B1. Ascorbic acid or sodium ascorbate is dissolved in deionized water to obtain an aqueous solution of ascorbic acid or sodium ascorbate, wherein the mass fraction of ascorbic acid or sodium ascorbate in the aqueous solution is 5.0-30.0 wt%; low-methoxyl pectin is added to the aqueous solution of ascorbic acid or sodium ascorbate, such that the mass ratio of pectin to ascorbic acid or sodium ascorbate is 0.01-0.10, wherein the degree of esterification of the low-methoxyl pectin is less than 50%; after the low-methoxyl pectin is dissolved under stirring, citric acid is added, wherein the amount of citric acid added is 0.1-2.0 wt% of the dry basis mass of the pectin, and the pH value of the system is gradually adjusted to 2.8-3.6; B2, under normal pressure and at a temperature of 5-25℃, the system is sheared and dispersed at a rotation speed of 500-8000 rpm while a calcium salt aqueous solution is added dropwise. The calcium salt aqueous solution is a deionized aqueous solution with a concentration of 10-50 mg / mL and is calculated as calcium ions. The dropping rate of the calcium salt aqueous solution is 0.5-10 mL / min. The mass ratio of the added calcium ions to the pectin is 0.03-0.20, where the mass of the pectin is the dry weight of the added pectin. The shearing and dispersion time is 5-30 min, resulting in a gel core particle dispersion containing ascorbic acid. B3. Preparation of pectin aqueous solution: Add low-methoxyl pectin to deionized water and stir until uniform and transparent to obtain a pectin aqueous solution. The pectin aqueous solution has a pectin mass fraction of 0.50-2.00 wt% and a pH value of 5.0-6.5. Add the pectin aqueous solution to the ascorbic acid-containing gel core particle dispersion, so that the mass ratio of the added pectin (dry basis) to the pectin in the ascorbic acid-containing gel core particle dispersion (dry basis) is 0.05-0.50. Add calcium salt aqueous solution again. The calcium salt aqueous solution is a deionized aqueous solution with a concentration of 10-50 mg / mL and is calculated as calcium ions. The dropping rate of the calcium salt aqueous solution is 0.5-10 mL / min. The mass ratio of the added calcium ions to the added pectin is 0.03-0.20. The cross-linking time is 5-30 min to form a shell layer. B4. The obtained core-shell microcapsule dispersion is centrifuged at a relative centrifugal force of 3000-8000g, a centrifugation time of 5-20min, and a centrifugation temperature of 4-25℃. The precipitate is collected to obtain wet core-shell microcapsules. The wet core-shell microcapsules are resuspended in deionized water and washed 1-3 times, with the volume of deionized water used in each wash being 3-10 times the volume of the wet core-shell microcapsules. After washing, centrifugation is performed again to obtain intermediate B. The particle size of the core-shell microcapsules is 1-50μm.

[0010] Furthermore, intermediate A used in the antioxidant jam is further prepared into intermediate AP, which is prepared through the following steps: C1, the intermediate A prepared according to steps A1-A4 is centrifuged, the relative centrifugal force of the centrifugation is 5000-10000g, the centrifugation time is 10-30min, and wet microgel is obtained; C2, the wet microgel is dried at an absolute pressure of 0.005-0.030 MPa and a temperature of 40-60℃ for 6-24 h to obtain intermediate AP; wherein the water content of intermediate AP is 0.5-8.0 wt%.

[0011] Furthermore, intermediate B used in the antioxidant jam is further prepared into intermediate BP, which is prepared through the following steps: D1, the intermediate B prepared according to steps B1-B4 is centrifuged, the relative centrifugal force of the centrifugation is 3000-8000g, the centrifugation time is 10-30min, and wet core-shell microcapsules are obtained. D2, the wet core-shell microcapsules are dried at an absolute pressure of 0.005-0.030 MPa and a temperature of 35-55℃ for 6-24 hours to obtain intermediate BP; wherein the water content of intermediate BP is 0.5-8.0 wt%.

[0012] Furthermore, the fruit raw materials are selected from one or more of the following: strawberry, blueberry, raspberry, blackberry, mango, peach, apricot, apple, and pear; It also includes 0.05-0.30 parts by weight of trisodium citrate dihydrate, wherein when the trisodium citrate dihydrate is included by weight, the total weight of the fruit raw material and sucrose does not exceed 91.15 parts.

[0013] As a concept of this invention, the present invention employs nanoscale pectin-calcium ion microgel and micron-scale core- The dual-layer synergistic design of the shell-microcapsule system aims to improve the processing compatibility, gel network stability, and ascorbic acid retention of jam systems under high solids conditions. The nanogels, by controlling the degree of ionic cross-linking between pectin and calcium ions under weakly acidic pH conditions, form particles with a diameter of 80-500 nm under shear dispersion. The micron-core-shell microcapsules are constructed through a two-step cross-linking strategy, creating a core-shell structure. The core encapsulates ascorbic acid or sodium ascorbate, while the outer shell forms a sustained-release layer. The differences in particle size and spatial distribution of the dual-layer microstructure help to balance processing compatibility, structural stability, and antioxidant activity retention.

[0014] This invention also discloses a method for preparing an antioxidant jam, comprising the following steps: S1 provides intermediate A or intermediate AP; S2 provides intermediate B or intermediate BP; S3: Mix fruit raw materials, sucrose and deionized water and heat to 60-95℃, maintain for 3-30 minutes and then concentrate under reduced pressure. S4, after cooling the material obtained in step S3 to 40-65℃, add intermediate A or intermediate AP, and intermediate B or intermediate BP, and mix for 5-30 minutes; add calcium salt as needed, so that the total amount of calcium ions added in the final antioxidant jam is 0.02-0.25 parts, which includes calcium ions introduced by intermediate A, calcium ions introduced by intermediate B, and calcium ions introduced by the added calcium salt; under stirring conditions, gradually adjust the pH of the system to 2.8-3.6 by adding citric acid. S5, the material obtained in step S4 is filled, sealed, and subjected to heat treatment at a temperature of 85-95°C for 10-30 minutes to obtain the antioxidant jam.

[0015] Furthermore, the absolute pressure of the vacuum concentration in step S3 is 0.010-0.060 MPa, and the temperature of the vacuum concentration is 55-75℃; the endpoint of the vacuum concentration in step S3 is: the soluble solids content of the material is 20-70°Bx, measured by a refractometer at 20℃, and after the vacuum concentration in step S3, the material is degassed under vacuum for 1-10 min.

[0016] In step S4, intermediate A or intermediate AP is added and mixed first, then intermediate B or intermediate BP is added and mixed. The mixing is performed by shear dispersion, and the rotation speed of the shear dispersion is 500-8000 rpm. The filling in step S5 is either hot filling or cold filling followed by heat treatment; The amount of citric acid added in steps A1 and B1 is 0.1-2.0 wt% of the dry basis weight of the pectin. When the calcium salt mentioned in steps A2, B2 and B3 is calcium chloride dihydrate, the concentration of the calcium salt aqueous solution is 10-50 mg / mL and calculated as calcium ions, and the dropping rate of the calcium salt aqueous solution is 0.5-10 mL / min. The shear dispersion described in step S4 is performed using a high-speed shear emulsifier or a homogenizer; The antioxidant activity of the antioxidant jam was evaluated by measuring its DPPH free radical scavenging capacity.

[0017] As another aspect of this invention, the invention employs a step-by-step introduction and a stepped thermo-mechanical treatment strategy. The preparation method helps improve the structural stability and functional retention of the bilayer microstructure throughout the jam preparation process. The key to the preparation process lies in controlling the introduction sequence, temperature window, and shear strength of intermediates A and B to achieve uniform dispersion of the nano-microgels in the jam matrix and maintain the micron-sized microcapsule encapsulation structure. In step S4, after the material is cooled to 40-65℃, intermediate A is introduced first, followed by intermediate B. Shear dispersion promotes their uniform distribution in the high-solids matrix. In the heat treatment stage of step S5, a process window of 85-95℃ and 10-30 min is used to complete the heat treatment. The pH value is controlled between 2.8 and 3.6 through the phased addition of citric acid and real-time monitoring. This pH range helps maintain the stability of the ionic crosslinking network and reduce ascorbic acid degradation.

[0018] Furthermore, the total ascorbic acid content in the final antioxidant jam is 50-500 mg / kg; when the core contains sodium ascorbate, the total content is converted to ascorbic acid based on the molar equivalent of ascorbic acid and sodium ascorbate.

[0019] Furthermore, after the final antioxidant jam is stored at 25°C in a sealed container away from light for 30 days, the retention rate of ascorbic acid is not less than 60%.

[0020] Furthermore, the encapsulation efficiency of the core-shell microcapsules is not less than 70%, and the encapsulation efficiency is determined by the following method: the core-shell microcapsules are dispersed in phosphate buffer solution with a pH of 7.0, and after standing at 25°C for 30 min, they are centrifuged to obtain supernatant and precipitate; the free ascorbic acid content in the supernatant is determined; another amount of core-shell microcapsule dispersion equal to the sample used before centrifugation is taken, broken, and the total ascorbic acid content is determined. The encapsulation efficiency is equal to the difference between the total ascorbic acid content and the free ascorbic acid content, divided by the total ascorbic acid content, and then multiplied by 100%.

[0021] Furthermore, in step B3, when preparing the pectin aqueous solution, mechanical stirring is used at 25°C with a stirring speed of 300-1200 rpm and a stirring time of 30-120 min until no visible agglomerates are found; the pH value of the pectin aqueous solution is adjusted dropwise to 5.0-6.5 using a 1.0 mol / L sodium hydroxide aqueous solution, and the pH value is directly measured at 25°C using a calibrated pH meter.

[0022] Furthermore, in step A1, when adding low-methoxyl pectin to deionized water, mechanical stirring is performed at 25°C with a stirring speed of 300-1200 rpm and a stirring time of 30-180 min; the citric acid is added in solid form in portions and the pH is measured in real time at 25°C.

[0023] Furthermore, in step B1, when ascorbic acid or sodium ascorbate is dissolved and added to low-methoxyl pectin, mechanical stirring is performed at 25°C with a stirring speed of 300-1200 rpm and a stirring time of 30-180 min to dissolve the low-methoxyl pectin; the citric acid is added in solid form in portions and the pH is measured in real time, with the pH value measured at 25°C.

[0024] Furthermore, the endpoint of the reduced pressure concentration in step S3 is: the soluble solids content of the material is 20-70°Bx, measured by a refractometer at 20°C.

[0025] Furthermore, in the encapsulation efficiency determination, the core-shell microcapsules are dispersed in 0.05 mol / L phosphate buffer solution with a solid content of 1.0-10.0 wt% at a pH of 7.0; the centrifugation separation is performed with a relative centrifugal force of 5000 g, a centrifugation time of 5 min, and a centrifugation temperature of 25 °C; the sample used for determining the total ascorbic acid content is crushed using a high-speed homogenizer with a homogenization speed of 10000-20000 rpm and a homogenization time of 1-5 min; the free ascorbic acid content and the total ascorbic acid content are both determined by liquid chromatography.

[0026] Furthermore, the ascorbic acid retention rate of the final antioxidant jam was determined after being stored in a sealed container at 25°C in the dark for 30 days. The retention rate was calculated as (ascorbic acid content on day 30 / initial ascorbic acid content) × 100%, where the initial ascorbic acid content was the total ascorbic acid content measured when the mixture was cooled to 25°C after the heat treatment in step S5.

[0027] Furthermore, the antioxidant activity of the antioxidant jam is expressed as the DPPH free radical scavenging rate, which is determined as follows: a 0.10 mmol / L DPPH ethanol solution is prepared, the sample is diluted with deionized water at a mass ratio of 1:20, and then mixed with the DPPH solution at a volume ratio of 1:1. The mixture is reacted at 25°C in the dark for 30 min, and the absorbance is measured at 517 nm. The scavenging rate is calculated as 1 - (A sample / A blank) × 100%; the DPPH free radical scavenging rate is not less than 30%.

[0028] This study analyzes the synergistic effects of intermediate A (nanogel) and intermediate B (microcapsule) in the jam system from the perspective of mechanism of action and synergistic effects. Intermediate A primarily functions to regulate the dispersion of the jam matrix and construct the gel network; intermediate B primarily functions to encapsulate and protect the active ingredients and regulate their release. The differences between intermediates A and B in particle size, spatial distribution, and functional localization contribute to improving the processing adaptability, structural stability, and retention of antioxidant activity in the jam system.

[0029] Beneficial technical effects 1. Improves processing compatibility and gel structure stability: through nano-scale pectin-calcium ion microcoagulation. The synergistic design of the gel and micron-sized core-shell microcapsules at a dual-scale helps to balance the processing adaptability and structural stability of the jam under high solids content conditions. The synergistic distribution of nanogels and micron-sized microcapsules in the matrix helps to improve the system's homogeneity and enhance its water-removal performance.

[0030] 2. Facilitates both ascorbic acid encapsulation and release regulation: A two-step cross-linking strategy is used to construct a bilayer structure of core-shell microcapsules. The core is used to encapsulate ascorbic acid, and the shell is used to form a sustained-release layer, which helps to achieve protection and release regulation of active ingredients in jam systems.

[0031] 3. Helps improve the retention of ascorbic acid under heat treatment and storage conditions: Through the spatial synergy and physical shielding effect of the bi-layer microstructure, it helps reduce the degradation risk of ascorbic acid during processing and storage, thereby improving the maintenance of antioxidant activity.

[0032] 4. It provides a systematic design method that takes into account processing adaptability, structural stability and retention of active ingredients: By differentiating the nano-phase and micro-phase in terms of particle size, spatial distribution and functional positioning, the bi-level microstructure forms a complementary and synergistic effect in the jam system. Attached Figure Description

[0033] Figure 1 The image shows a comparison of the XRD / XRPD spectra of Example 1, Comparative Example 6, and Comparative Example 7.

[0034] Figure 2 The image shows a comparison of the FTIR spectra of Example 1, Comparative Example 1, and Comparative Example 2.

[0035] Figure 3 The images show the laser particle size differential volume distribution diagrams for Examples 1, 3, and 4.

[0036] Figure 4 The cumulative volume distribution of laser particle size is shown in Example 1, Comparative Example 3, and Comparative Example 4.

[0037] Figure 5 The cumulative release curves (pH 2.0) of ascorbic acid for Example 1 and Comparative Example 5 are shown.

[0038] Figure 6 The graph shows the cumulative release curves (pH 3.0) of ascorbic acid for Example 1 and Comparative Example 5.

[0039] Figure 7 The graph shows the cumulative release curves (pH 4.0) of ascorbic acid for Example 1 and Comparative Example 5.

[0040] Figure 8 The graph shows the cumulative release curves (pH 7.0) of ascorbic acid for Example 1 and Comparative Example 5.

[0041] Figure 9 This is a macroscopic image of the antioxidant jam prepared in Example 1.

[0042] Figure 10 This is a scanning electron microscope image of the antioxidant jam from Example 1.

[0043] Figure 11 This is a transmission electron microscope (TEM) image of an ultrathin section of the shell / core structure of the core-shell microcapsule in Example 1. Detailed Implementation

[0044] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings.

[0045] Example 1 This embodiment provides an antioxidant jam, comprising the following components by weight: 35.00 parts strawberry puree, 17.50 parts blueberry puree, 35.00 parts sucrose, 0.40 parts citric acid, and a total calcium ion addition of 0.13 parts based on calcium ion mass. The calcium ion sources in this embodiment include calcium ions introduced by intermediate A, calcium ions introduced by intermediate B, and calcium ions introduced by the supplementary addition of calcium chloride dihydrate. The amount of calcium chloride dihydrate added in this embodiment is 0.06 parts. Intermediate AP is 1.20 parts (based on dry solids, deducting the converted mass of calcium ions contained therein), intermediate B is 2.50 parts (based on dry solids, deducting the converted mass of calcium ions contained therein), and deionized water is 8.27 parts (including water introduced by the dispersion of intermediate B, residual water of intermediate AP, and separately added deionized water), making the total weight of the above components 100 parts. In this embodiment, the total mass of fruit ingredients and sucrose is 52.50 + 35.00 = 87.50 parts, which does not exceed 91.45 parts. The pH value of the antioxidant jam in this embodiment is 3.2.

[0046] The intermediate AP in this embodiment was obtained by drying a pectin-calcium ion microgel dispersion after solid-liquid separation. The pectin-calcium ion microgel dispersion in this embodiment was obtained by forming an ionic cross-linking network between pectin and calcium ions under a pH of 3.7 and then dispersing it by shearing. The particle size of the microgel particles in the pectin-calcium ion microgel dispersion in this embodiment was 250 nm. The particle size in this embodiment was the Z-mean hydrated particle size measured by dynamic light scattering method. The dynamic light scattering method was used for measurement at a test temperature of 25°C. The sample was diluted with deionized water to a solid content of 0.05 wt% before measurement.

[0047] Intermediate B in this embodiment is a core-shell microcapsule dispersion. The core-shell microcapsules in this embodiment include a core and a shell. The core contains ascorbic acid, and the shell contains an ionic cross-linked network formed by pectin and calcium ions. The particle size of the core-shell microcapsules in this embodiment is 20 μm. The particle size in this embodiment is the median diameter D50 of the volume distribution measured by a laser particle size analyzer at a testing temperature of 25°C. The sample was diluted with deionized water to a solid content of 0.5 wt% before measurement. Intermediate A in this embodiment is used in the form of intermediate AP after solid-liquid separation and drying. Intermediate B in this embodiment is used in the form of a core-shell microcapsule dispersion.

[0048] Intermediate AP in this embodiment is prepared through the following steps: First, intermediate A is prepared, including the following steps: A1, low-methoxyl pectin is added to deionized water to prepare a pectin aqueous solution. The pectin aqueous solution in this embodiment has a pectin mass fraction of 1.20 wt%, and the degree of esterification of the low-methoxyl pectin in this embodiment is 38%. Mechanical stirring is performed at 25°C, the stirring speed is 600 rpm, and the stirring time is 90 min. Citric acid is added under stirring conditions. In this embodiment, the citric acid is added in solid form in portions, and the pH is measured in real time. The amount of citric acid added in this embodiment is 0.8 wt% of the dry basis mass of the pectin in this embodiment. The pH value of the pectin aqueous solution in this embodiment is gradually adjusted to 3.7, and the pH value is measured at 25°C. A2. Under normal pressure and at a temperature of 20°C, the pectin aqueous solution of this embodiment was sheared and dispersed at a rotation speed of 4000 rpm, while calcium chloride dihydrate aqueous solution was added dropwise. The calcium chloride dihydrate aqueous solution of this embodiment was a deionized aqueous solution with a concentration of 30 mg / mL and calculated as calcium ions. The dropping rate of the calcium chloride dihydrate aqueous solution of this embodiment was 5.0 mL / min. The mass ratio of the added calcium ions to the pectin of this embodiment was 0.08, where the mass of the pectin of this embodiment was the dry basis mass of the added pectin. The shearing and dispersion time was 15 min.

[0049] A3, when the mass ratio of added calcium ions to pectin in this embodiment reaches 0.08, stop adding the solution and continue shearing and dispersing for 8 minutes.

[0050] A4. The obtained dispersion is filtered through a sieve with a pore size of 300 μm, and the filtrate is collected to obtain intermediate A; wherein, the solid content of intermediate A in this embodiment is 1.50 wt%, and the particle size of the microgel particles in this embodiment is 250 nm.

[0051] The intermediate AP of this embodiment is further prepared by the following steps: C1, the intermediate A obtained above is centrifuged. The relative centrifugal force for centrifugation in this embodiment is 7000g, and the centrifugation time is 15min, to obtain a wet microgel. C2, the wet microgel of this embodiment is dried at an absolute pressure of 0.020MPa and a temperature of 50°C for 10h to obtain intermediate AP; wherein, the water content of intermediate AP in this embodiment is 4.0wt%. The preparation method of intermediate B in this embodiment includes the following steps: B1, dissolving ascorbic acid in deionized water to obtain an ascorbic acid aqueous solution, wherein the mass fraction of ascorbic acid in the ascorbic acid aqueous solution in this embodiment is 17.5 wt%; adding low-methoxyl pectin to the ascorbic acid aqueous solution in this embodiment, such that the mass ratio of pectin to ascorbic acid in this embodiment is 0.055, wherein the degree of esterification of the low-methoxyl pectin in this embodiment is 38%; dissolving the low-methoxyl pectin in this embodiment by mechanical stirring at 25°C, stirring speed of 600 rpm, and stirring time of 90 min; after dissolving the low-methoxyl pectin in this embodiment under stirring conditions, adding citric acid, wherein the citric acid in this embodiment is added in solid form in portions and the pH is measured in real time, wherein the amount of citric acid added in this embodiment is 0.8 wt% of the dry basis mass of the pectin in this embodiment, and gradually adjusting the pH value of the system to 3.2, wherein the pH value is measured at 25°C.

[0052] B2. Under normal pressure and at a temperature of 15°C, the system of this embodiment was sheared and dispersed at a rotation speed of 4000 rpm while calcium chloride dihydrate aqueous solution was added dropwise. The calcium chloride dihydrate aqueous solution in this embodiment was a deionized aqueous solution with a concentration of 30 mg / mL, calculated as calcium ions. The dropping rate of the calcium chloride dihydrate aqueous solution in this embodiment was 5.0 mL / min. The mass ratio of the added calcium ions to the pectin in this embodiment was 0.10, where the mass of the pectin in this embodiment was the dry basis mass of the added pectin. The shearing and dispersion time was 15 min, resulting in a gel core particle dispersion containing ascorbic acid.

[0053] B3. Preparation of pectin aqueous solution: Low-methoxyl pectin was added to deionized water and mechanically stirred at 600 rpm for 60 minutes at 25°C until no visible agglomerates were observed. The pH of the pectin aqueous solution in this example was adjusted dropwise to 5.8 using a 1.0 mol / L sodium hydroxide aqueous solution. The pH value was directly measured at 25°C using a calibrated pH meter. The solution was stirred until homogeneous and transparent to obtain a pectin aqueous solution. The mass fraction of pectin in the pectin aqueous solution of this example was 1.20 wt%, and the pH value of the pectin aqueous solution in this example was 5.8. [The text then abruptly shifts to a seemingly unrelated topic:] ...to the ascorbic acid-containing... A pectin aqueous solution of this embodiment is added to the gel core particle dispersion, such that the mass ratio of the added pectin (dry basis) to the pectin in the ascorbic acid-containing gel core particle dispersion of this embodiment (dry basis) is 0.25. A calcium chloride dihydrate aqueous solution is then added dropwise. The calcium chloride dihydrate aqueous solution of this embodiment is a deionized aqueous solution with a concentration of 30 mg / mL, calculated as calcium ions. The dropping rate of the calcium chloride dihydrate aqueous solution of this embodiment is 5.0 mL / min. The mass ratio of the added calcium ions to the added pectin of this embodiment is 0.10, and the crosslinking time is 15 min to form a shell layer.

[0054] B4. The obtained core-shell microcapsule dispersion was centrifuged. In this embodiment, the relative centrifugal force was 5000g, the centrifugation time was 12min, and the centrifugation temperature was 15℃. The precipitate was collected to obtain wet core-shell microcapsules. The wet core-shell microcapsules of this embodiment were resuspended in deionized water and washed twice. The volume of deionized water used for each wash was 5 times the volume of the wet core-shell microcapsules of this embodiment. After washing, centrifugation was performed again. The precipitate was collected and resuspended in deionized water to obtain intermediate B (core-shell microcapsule dispersion). The particle size of the core-shell microcapsules in this embodiment was 20μm.

[0055] The preparation method of the antioxidant jam in this embodiment includes the following steps: S1, providing intermediate AP. S2, providing intermediate B. S3, mixing 35.00 parts of strawberry puree, 17.50 parts of blueberry puree, 35.00 parts of sucrose, and deionized water, heating to 75°C, maintaining for 15 minutes, and then performing vacuum concentration; the absolute pressure of vacuum concentration in this embodiment is 0.035 MPa, the temperature of vacuum concentration in this embodiment is 65°C, and the endpoint of vacuum concentration in this embodiment is: the soluble solids content of the material is 45°Bx, measured by a refractometer at 20°C; after vacuum concentration in this embodiment, degassing is performed under reduced pressure for 5 minutes.

[0056] S4. After cooling the material obtained in step S3 to 50°C, the mixing in this embodiment is performed by shear dispersion. The shear dispersion speed in this embodiment is 4000 rpm. The shear dispersion in this embodiment is performed using a high-speed shear emulsifier. First, add intermediate AP of this embodiment and mix, then add intermediate B of this embodiment and mix, mixing for 15 minutes. If necessary, add 0.06 parts of calcium chloride dihydrate, so that the total amount of calcium ions added in the final antioxidant jam is 0.13 parts in terms of calcium ions. The total amount of calcium ions added in this embodiment includes calcium ions introduced by intermediate A, calcium ions introduced by intermediate B, and calcium ions introduced by the added calcium chloride dihydrate. Under stirring conditions, add 0.40 parts of citric acid to gradually adjust the pH value of the system to 3.2. The amount of citric acid added in this embodiment is counted as the mass part of citric acid.

[0057] S5, the material obtained in step S4 is filled, sealed, and heat-treated. In this embodiment, the heat treatment temperature is 90°C and the heat treatment time is 20 minutes, resulting in the antioxidant jam of this embodiment. The filling in this embodiment is hot filling.

[0058] The total ascorbic acid content in the final antioxidant jam of this embodiment is 280 mg / kg. The ascorbic acid retention rate of the final antioxidant jam of this embodiment was determined after 30 days of sealed storage at 25°C in the dark. The retention rate in this embodiment was calculated as (ascorbic acid content on day 30 / initial ascorbic acid content) × 100%, where the initial ascorbic acid content was the total ascorbic acid content measured after cooling to 25°C following the heat treatment in step S5. The ascorbic acid retention rate of the final antioxidant jam of this embodiment was 68% after 30 days of sealed storage at 25°C in the dark.

[0059] The encapsulation efficiency of the core-shell microcapsules in this embodiment is 78%. The encapsulation efficiency was determined by the following method: The core-shell microcapsules of this embodiment were dispersed at a solid content of 5.0 wt% in 0.05 mol / L phosphate buffer solution with a pH of 7.0. After standing at 25°C for 30 min, the mixture was centrifuged to obtain the supernatant and precipitate. The centrifugation force in this embodiment was 5000 g, the centrifugation time was 5 min, and the centrifugation temperature was 25°C. The free ascorbic acid content in the supernatant of this embodiment was determined. A separate sample containing the same amount of the core-shell microcapsule dispersion used before centrifugation was taken, and the total ascorbic acid content was determined after crushing. In this embodiment, the sample used to determine the total ascorbic acid content was crushed using a high-speed homogenizer at a speed of 15,000 rpm for 3 minutes. The encapsulation efficiency in this embodiment is equal to the difference between the total ascorbic acid content and the free ascorbic acid content, divided by the total ascorbic acid content, and then multiplied by 100%. Both the free ascorbic acid content and the total ascorbic acid content in this embodiment were determined by liquid chromatography.

[0060] The antioxidant activity of the antioxidant jam in this embodiment was evaluated by measuring its DPPH free radical scavenging ability. The antioxidant activity of the antioxidant jam in this embodiment was expressed as the DPPH free radical scavenging rate, which was determined as follows: a 0.10 mmol / L DPPH ethanol solution was prepared, and the sample was diluted with deionized water at a mass ratio of 1:20 and then mixed with the DPPH solution at a volume ratio of 1:1. The mixture was reacted at 25°C in the dark for 30 min, and the absorbance was measured at 517 nm. The scavenging rate was calculated as 1 - (A sample / A blank) × 100%. The DPPH free radical scavenging rate in this embodiment was 42%.

[0061] Features of the scheme in Example 1: This embodiment employs a moderate formulation design, using 52.50 parts of fruit raw materials (a blend of strawberry and blueberry), 35.00 parts of sucrose, 1.20 parts of intermediate AP, 2.50 parts of intermediate B, 0.13 parts of total calcium ions, a pH of 3.2, a final ascorbic acid content of 280 mg / kg, a 30-day retention rate of 68%, an encapsulation rate of 78%, and a DPPH scavenging rate of 42%. Intermediate AP is in dry powder form with 4.0 wt% moisture; intermediate B is in dispersion form with microgel particle size of 250 nm and core-shell microcapsule particle size of 20 μm. The preparation process parameters are balanced and stable: pectin concentration 1.20 wt%, preparation temperature 15-20℃, shear speed 4000 rpm, calcium ion / pectin mass ratio 0.08-0.10, and heat treatment temperature 90℃ for 20 min. This formula is suitable for large-scale, stable production of strawberry and blueberry blended jam products for the mass consumer market. It has both good antioxidant properties and sensory quality, and is suitable for use as a bread spread, baking filling, and yogurt ingredient.

[0062] Example 2: High Fruit Content Antioxidant Jam Formula This embodiment provides an antioxidant jam, comprising the following components by weight: 65.00 parts mango puree, 20.00 parts sucrose, 0.60 parts citric acid, 0.20 parts trisodium citrate dihydrate, and a total calcium ion addition of 0.18 parts. The calcium ion sources in this embodiment include calcium ions introduced by intermediate A, calcium ions introduced by intermediate B, and calcium ions introduced by supplementary calcium lactate. The amount of calcium lactate added in this embodiment is 0.32 parts. Intermediate AP consists of 1.80 parts (based on dry solids, deducting the equivalent mass of calcium ions contained therein), intermediate B consists of 3.50 parts (based on dry solids, deducting the equivalent mass of calcium ions contained therein), and deionized water consists of 8.72 parts (including water introduced by the dispersion of intermediate B, residual water of intermediate AP, and separately added deionized water), making the total weight of the above components 100 parts.

[0063] In this embodiment, intermediate AP is obtained by drying a pectin-calcium ion microgel dispersion after solid-liquid separation. The pectin-calcium ion microgel dispersion is obtained by forming an ionic cross-linking network between pectin and calcium ions at a pH of 3.5 and then dispersing it by shearing. The particle size of the microgel particles in the pectin-calcium ion microgel dispersion is 150 nm. The particle size in this embodiment is the Z-mean hydrated particle size measured by dynamic light scattering method. The dynamic light scattering method is used for measurement at a test temperature of 25 °C. The sample is diluted with deionized water to a solid content of 0.08 wt% before measurement.

[0064] Intermediate B in this embodiment is a core-shell microcapsule dispersion. The core-shell microcapsules in this embodiment include a core and a shell. The core contains sodium ascorbate, and the shell contains an ionic cross-linked network formed by pectin and calcium ions. The particle size of the core-shell microcapsules in this embodiment is 30 μm. The particle size in this embodiment is the median diameter D50 of the volume distribution, measured by a laser particle size analyzer at 25°C. The sample was diluted with deionized water to a solid content of 0.8 wt% before measurement. Intermediate A in this embodiment is used in the form of intermediate AP after solid-liquid separation and drying. Intermediate B in this embodiment is used in the form of a core-shell microcapsule dispersion.

[0065] Intermediate AP in this embodiment is prepared by the following steps: First, intermediate A is prepared, including the following steps: A1, low-methoxyl pectin is added to deionized water to prepare a pectin aqueous solution. The pectin aqueous solution in this embodiment has a pectin mass fraction of 1.50 wt%, and the degree of esterification of the low-methoxyl pectin in this embodiment is 35%. Mechanical stirring is carried out at 25°C, the stirring speed is 800 rpm, and the stirring time is 120 min. Citric acid is added under stirring conditions. In this embodiment, citric acid is added in solid form in portions and the pH is measured in real time. The amount of citric acid added in this embodiment is 1.2 wt% of the dry basis mass of the pectin in this embodiment. The pH value of the pectin aqueous solution in this embodiment is gradually adjusted to 3.5, and the pH value is measured at 25°C.

[0066] A2. Under normal pressure and at a temperature of 15°C, the pectin aqueous solution of this embodiment was sheared and dispersed at a rotation speed of 6000 rpm, while calcium chloride dihydrate aqueous solution was added dropwise. The calcium chloride dihydrate aqueous solution in this embodiment was a deionized aqueous solution with a concentration of 40 mg / mL, calculated as calcium ions. The dropping rate of the calcium chloride dihydrate aqueous solution in this embodiment was 7.0 mL / min. The mass ratio of the added calcium ions to the pectin in this embodiment was 0.11, where the mass of the pectin in this embodiment was the dry basis mass of the added pectin. The shearing and dispersion time was 20 min.

[0067] A3. When the mass ratio of the added calcium ions to the pectin in this embodiment reaches 0.11, stop adding the solution and continue shearing and dispersing for 10 minutes.

[0068] A4. The obtained dispersion is filtered through a sieve with a pore size of 200 μm, and the filtrate is collected to obtain intermediate A; wherein, the solid content of intermediate A in this embodiment is 2.00 wt%, and the particle size of the microgel particles in this embodiment is 150 nm.

[0069] The intermediate AP in this embodiment is further prepared by the following steps: C1, the intermediate A obtained above is centrifuged. The relative centrifugal force for centrifugation in this embodiment is 7500g, and the centrifugation time is 20min, to obtain a wet microgel. C2, the wet microgel of this embodiment is dried at an absolute pressure of 0.015MPa and a temperature of 50°C for 12h to obtain intermediate AP; wherein, the water content of intermediate AP in this embodiment is 3.0wt%.

[0070] The preparation method of intermediate B in this embodiment includes the following steps: B1, dissolving sodium ascorbate in deionized water to obtain an aqueous solution of sodium ascorbate, wherein the mass fraction of sodium ascorbate in the aqueous solution of sodium ascorbate in this embodiment is 22.0 wt%; adding low-methoxyl pectin to the aqueous solution of sodium ascorbate in this embodiment, such that the mass ratio of pectin to sodium ascorbate in this embodiment is 0.070, wherein the degree of esterification of the low-methoxyl pectin in this embodiment is 35%; dissolving the low-methoxyl pectin in this embodiment by mechanical stirring at 25°C, stirring speed of 800 rpm, and stirring time of 120 min; after dissolving the low-methoxyl pectin in this embodiment under stirring conditions, adding citric acid, wherein the citric acid in this embodiment is added in solid form in portions and the pH is measured in real time, wherein the amount of citric acid added in this embodiment is 1.2 wt% of the dry basis mass of pectin in this embodiment, and gradually adjusting the pH value of the system to 3.0, wherein the pH value is measured at 25°C.

[0071] B2. Under normal pressure and at a temperature of 10°C, the system of this embodiment was sheared and dispersed at a rotation speed of 6000 rpm while calcium chloride dihydrate aqueous solution was added dropwise. The calcium chloride dihydrate aqueous solution in this embodiment was a deionized aqueous solution with a concentration of 40 mg / mL, calculated as calcium ions. The dropping rate of the calcium chloride dihydrate aqueous solution in this embodiment was 7.0 mL / min. The mass ratio of the added calcium ions to the pectin in this embodiment was 0.15, where the mass of the pectin in this embodiment was the dry basis mass of the added pectin. The shearing and dispersion time was 20 min, resulting in a gel core particle dispersion containing ascorbic acid.

[0072] B3. Preparation of pectin aqueous solution: Low-methoxyl pectin was added to deionized water and mechanically stirred at 800 rpm for 80 minutes at 25°C until no visible agglomerates were observed. The pH of the pectin aqueous solution in this example was adjusted dropwise to 6.0 using a 1.0 mol / L sodium hydroxide aqueous solution. The pH value was directly measured at 25°C using a calibrated pH meter. The solution was stirred until homogeneous and transparent to obtain a pectin aqueous solution. The mass fraction of pectin in the pectin aqueous solution of this example was 1.50 wt%, and the pH value of the pectin aqueous solution in this example was 6.0. [The text then abruptly shifts to a seemingly unrelated topic:] ...to the ascorbic acid-containing... A pectin aqueous solution of this embodiment is added to the gel core particle dispersion, such that the mass ratio of the added pectin (dry basis) to the pectin in the ascorbic acid-containing gel core particle dispersion of this embodiment (dry basis) is 0.35; a calcium chloride dihydrate aqueous solution is added dropwise again. The calcium chloride dihydrate aqueous solution of this embodiment is a deionized aqueous solution with a concentration of 40 mg / mL and is calculated as calcium ions. The dropping rate of the calcium chloride dihydrate aqueous solution of this embodiment is 7.0 mL / min; the mass ratio of the added calcium ions to the added pectin of this embodiment is 0.15, and the crosslinking time is 20 min to form a shell layer.

[0073] B4. The obtained core-shell microcapsule dispersion was centrifuged. In this embodiment, the relative centrifugal force was 6000g, the centrifugation time was 15min, and the centrifugation temperature was 10℃. The precipitate was collected to obtain wet core-shell microcapsules. The wet core-shell microcapsules of this embodiment were resuspended in deionized water and washed twice. The volume of deionized water used for each wash was 6 times the volume of the wet core-shell microcapsules of this embodiment. After washing, centrifugation was performed again. The precipitate was collected and resuspended in deionized water to obtain intermediate B (core-shell microcapsule dispersion). The particle size of the core-shell microcapsules in this embodiment was 30μm.

[0074] The preparation method of the antioxidant jam in this embodiment includes the following steps: S1, providing intermediate AP. S2, providing intermediate B. S3, mixing 65.00 parts of mango puree, 20.00 parts of sucrose, and deionized water, heating to 85°C, maintaining for 20 minutes, and then concentrating under reduced pressure; the absolute pressure of the reduced pressure concentration in this embodiment is 0.045 MPa, the temperature of the reduced pressure concentration in this embodiment is 70°C, and the endpoint of the reduced pressure concentration in this embodiment is: the soluble solids content of the material is 55°Bx, measured by a refractometer at 20°C; after the reduced pressure concentration in this embodiment, degassing is performed under reduced pressure for 7 minutes.

[0075] S4. After cooling the material obtained in step S3 to 55°C, the mixing in this embodiment is performed by shear dispersion. The shear dispersion speed in this embodiment is 6000 rpm. The shear dispersion in this embodiment is performed using a homogenizer. First, intermediate AP of this embodiment is added and mixed, then intermediate B of this embodiment is added and mixed, and the mixture is mixed for 20 minutes. If necessary, 0.32 parts of calcium lactate are added so that the total amount of calcium ions added in the final antioxidant jam is 0.18 parts in terms of calcium ions. The total amount of calcium ions added in this embodiment includes the calcium ions introduced by intermediate A, the calcium ions introduced by intermediate B, and the calcium ions introduced by the added calcium lactate. Under stirring conditions, 0.60 parts of citric acid and 0.20 parts of trisodium citrate dihydrate are added to gradually adjust the pH value of the system to 3.0. The amount of citric acid added in this embodiment is counted as the mass fraction of citric acid.

[0076] S5, the material obtained in step S4 is filled, sealed, and heat-treated. In this embodiment, the heat treatment temperature is 90°C and the heat treatment time is 25 minutes, resulting in the antioxidant jam of this embodiment. The filling in this embodiment is hot filling.

[0077] The total ascorbic acid content in the final antioxidant jam of this embodiment, converted to ascorbic acid based on the molar equivalent of ascorbic acid and sodium ascorbate, is 365 mg / kg. The ascorbic acid retention rate of the final antioxidant jam of this embodiment was determined after 30 days of sealed storage at 25°C in the dark. The retention rate in this embodiment was calculated as (ascorbic acid content on day 30 / initial ascorbic acid content) × 100%, where the initial ascorbic acid content was the total ascorbic acid content measured after cooling to 25°C following the heat treatment in step S5. The ascorbic acid retention rate of the final antioxidant jam of this embodiment was 72% after 30 days of sealed storage at 25°C in the dark.

[0078] The encapsulation efficiency of the core-shell microcapsules in this embodiment is 82%. The encapsulation efficiency was determined by the following method: The core-shell microcapsules of this embodiment were dispersed at a solid content of 6.0 wt% in 0.05 mol / L phosphate buffer solution with a pH of 7.0. After standing at 25°C for 30 min, the mixture was centrifuged to obtain the supernatant and precipitate. The centrifugation force in this embodiment was 5000 g, the centrifugation time was 5 min, and the centrifugation temperature was 25°C. The free ascorbic acid content in the supernatant of this embodiment was measured. The acid content and the total ascorbic acid content in the precipitate of this embodiment were determined. The total ascorbic acid content of the precipitate in this embodiment was determined after crushing. The sample used to determine the total ascorbic acid content in this embodiment was crushed using a high-speed homogenizer with a homogenization speed of 18,000 rpm and a homogenization time of 4 min. The encapsulation efficiency in this embodiment was equal to the difference between the total ascorbic acid content and the free ascorbic acid content, divided by the total ascorbic acid content and multiplied by 100%. The free ascorbic acid content and the total ascorbic acid content in this embodiment were both determined by liquid chromatography.

[0079] The antioxidant activity of the antioxidant jam in this embodiment was evaluated by measuring its DPPH free radical scavenging ability. The antioxidant activity of the antioxidant jam in this embodiment was expressed as the DPPH free radical scavenging rate, which was determined as follows: a 0.10 mmol / L DPPH ethanol solution was prepared, and the sample was diluted with deionized water at a mass ratio of 1:20 and then mixed with the DPPH solution at a volume ratio of 1:1. The mixture was reacted at 25°C in the dark for 30 min, and the absorbance was measured at 517 nm. The scavenging rate was calculated as 1 - (A sample / A blank) × 100%. The DPPH free radical scavenging rate in this embodiment was 48%.

[0080] Features of the scheme in Example 2: This embodiment uses a high-fruit-content formulation: 65.00 parts mango puree, 20.00 parts sucrose, 1.80 parts intermediate AP, 3.50 parts intermediate B, 0.18 parts calcium ions, and 0.20 parts trisodium citrate dihydrate. The pH is 3.0, ascorbic acid content is 365 mg / kg, 30-day retention rate is 72%, encapsulation rate is 82%, and DPPH scavenging rate is 48%. Intermediate AP is in dry powder form with 3.0 wt% moisture; intermediate B is in dispersion form with microgel particle size of 150 nm and core-shell microcapsule particle size of 30 μm. Process parameters: pectin concentration 1.50 wt%, preparation temperature 10-15℃, shear speed 6000 rpm, calcium ion / pectin mass ratio 0.11-0.15, heat treatment at 90℃ for 25 min, and concentration to 55°Bx. This formula is low in sugar and high in fruit pulp, making it suitable for low-sugar health foods, sports nutrition supplements, children's meals, and functional breakfast ingredients.

[0081] Example 3: High sucrose content antioxidant jam formula This embodiment provides an antioxidant jam, comprising the following components by weight: 25.00 parts raspberry berries, 15.00 parts blackberry pulp, 48.00 parts sucrose, 0.25 parts citric acid, and 0.08 parts total calcium ions. The calcium ions in this embodiment originate from calcium ions introduced by intermediate A and intermediate B, without the need for additional calcium salts. Intermediate AP comprises 0.60 parts (based on dry solids, minus the equivalent mass of calcium ions contained therein), intermediate B comprises 1.50 parts (based on dry solids, minus the equivalent mass of calcium ions contained therein), and deionized water comprises 9.57 parts (including water introduced by the dispersion of intermediate B, residual water from intermediate AP, and additionally added deionized water), bringing the total weight of all components to 100 parts. In this embodiment, the total mass of fruit ingredients and sucrose is 40.00 + 48.00 = 88.00 parts, which does not exceed 91.45 parts. The pH value of the antioxidant jam in this embodiment is 3.4.

[0082] The intermediate AP in this embodiment was obtained by drying a pectin-calcium ion microgel dispersion after solid-liquid separation. The pectin-calcium ion microgel dispersion in this embodiment was obtained by forming an ionic cross-linking network between pectin and calcium ions under a pH of 4.0 and then dispersing it by shearing. The particle size of the microgel particles in the pectin-calcium ion microgel dispersion in this embodiment was 400 nm. The particle size in this embodiment was the Z-mean hydrated particle size measured by dynamic light scattering method. The dynamic light scattering method was used for measurement at a test temperature of 25°C. The sample was diluted with deionized water to a solid content of 0.03 wt% before measurement.

[0083] Intermediate B in this embodiment is a core-shell microcapsule dispersion. The core-shell microcapsules in this embodiment include a core and a shell. The core contains ascorbic acid, and the shell contains an ionic cross-linked network formed by pectin and calcium ions. The particle size of the core-shell microcapsules in this embodiment is 10 μm. The particle size in this embodiment is the median diameter D50 of the volume distribution measured by a laser particle size analyzer at a test temperature of 25°C. The sample was diluted with deionized water to a solid content of 0.3 wt% before measurement. Intermediate A in this embodiment is used in the form of intermediate AP after solid-liquid separation and drying. Intermediate B in this embodiment is used in the form of a core-shell microcapsule dispersion.

[0084] Intermediate AP in this embodiment is prepared by the following steps: First, intermediate A is prepared, including the following steps: A1, low-methoxyl pectin is added to deionized water to prepare a pectin aqueous solution. The pectin aqueous solution in this embodiment has a pectin mass fraction of 0.80 wt%, and the degree of esterification of the low-methoxyl pectin in this embodiment is 42%. Mechanical stirring is carried out at 25°C, the stirring speed is 500 rpm, and the stirring time is 60 min. Citric acid is added under stirring conditions. In this embodiment, citric acid is added in solid form in portions and the pH is measured in real time. The amount of citric acid added in this embodiment is 0.5 wt% of the dry basis mass of the pectin in this embodiment. The pH value of the pectin aqueous solution in this embodiment is gradually adjusted to 4.0, and the pH value is measured at 25°C.

[0085] A2. Under normal pressure and at a temperature of 25°C, the pectin aqueous solution of this embodiment was sheared and dispersed at a rotation speed of 2500 rpm, while calcium chloride dihydrate aqueous solution was added dropwise. The calcium chloride dihydrate aqueous solution of this embodiment was a deionized aqueous solution with a concentration of 20 mg / mL and calculated as calcium ions. The dropping rate of the calcium chloride dihydrate aqueous solution of this embodiment was 2.5 mL / min. The mass ratio of the added calcium ions to the pectin of this embodiment was 0.05, where the mass of the pectin of this embodiment was the dry basis mass of the added pectin. The shearing and dispersion time was 10 min.

[0086] A3. When the mass ratio of the added calcium ions to the pectin in this embodiment reaches 0.05, stop adding the solution and continue shearing and dispersing for 5 minutes.

[0087] A4, the obtained dispersion was filtered through a sieve with a pore size of 400 μm, and the filtrate was collected to obtain intermediate A; wherein.

[0088] In this embodiment, the solid content of intermediate A is 1.00 wt%, and the particle size of the microgel particles is 400 nm. Intermediate AP in this embodiment is further prepared by the following steps: C1, the intermediate A obtained above is centrifuged. The relative centrifugal force for centrifugation in this embodiment is 6000 g, and the centrifugation time is 12 min, to obtain a wet microgel. C2, the wet microgel of this embodiment is dried at an absolute pressure of 0.025 MPa and a temperature of 45°C for 8 h to obtain intermediate AP; wherein, the water content of intermediate AP in this embodiment is 5.0 wt%.

[0089] The preparation method of intermediate B in this embodiment includes the following steps: B1, dissolving ascorbic acid in deionized water to obtain an ascorbic acid aqueous solution, wherein the mass fraction of ascorbic acid in the ascorbic acid aqueous solution in this embodiment is 12.0 wt%; adding low-methoxyl pectin to the ascorbic acid aqueous solution in this embodiment, such that the mass ratio of pectin to ascorbic acid in this embodiment is 0.035, wherein the degree of esterification of the low-methoxyl pectin in this embodiment is 42%; dissolving the low-methoxyl pectin in this embodiment by mechanical stirring at 25°C, stirring speed of 500 rpm, and stirring time of 60 min; after dissolving the low-methoxyl pectin in this embodiment under stirring conditions, adding citric acid, wherein the citric acid in this embodiment is added in solid form in portions and the pH is measured in real time, wherein the amount of citric acid added in this embodiment is 0.5 wt% of the dry basis mass of the pectin in this embodiment, and gradually adjusting the pH value of the system to 3.4, wherein the pH value is measured at 25°C.

[0090] B2. Under normal pressure and at a temperature of 20°C, the system of this embodiment was sheared and dispersed at a rotation speed of 2500 rpm while calcium chloride dihydrate aqueous solution was added dropwise. The calcium chloride dihydrate aqueous solution in this embodiment was a deionized aqueous solution with a concentration of 20 mg / mL, calculated as calcium ions. The dropping rate of the calcium chloride dihydrate aqueous solution in this embodiment was 2.5 mL / min. The mass ratio of the added calcium ions to the pectin in this embodiment was 0.07, where the mass of the pectin in this embodiment was the dry basis mass of the added pectin. The shearing and dispersion time was 10 min, resulting in a gel core particle dispersion containing ascorbic acid.

[0091] B3. Preparation of pectin aqueous solution: Low-methoxyl pectin was added to deionized water and mechanically stirred at 500 rpm for 50 minutes at 25°C until no visible agglomerates were observed. The pH of the pectin aqueous solution in this example was adjusted dropwise to 5.5 using a 1.0 mol / L sodium hydroxide aqueous solution. The pH value was directly measured at 25°C using a calibrated pH meter. The solution was stirred until homogeneous and transparent to obtain a pectin aqueous solution. The mass fraction of pectin in the pectin aqueous solution of this example was 0.80 wt%, and the pH value of the pectin aqueous solution in this example was 5.5. [The text then abruptly shifts to a seemingly unrelated topic:] ...to the ascorbic acid-containing... A pectin aqueous solution of this embodiment is added to the gel core particle dispersion, such that the mass ratio of the added pectin (on a dry basis) to the pectin in the ascorbic acid-containing gel core particle dispersion of this embodiment (on a dry basis) is 0.15. A calcium chloride dihydrate aqueous solution is then added dropwise. The calcium chloride dihydrate aqueous solution of this embodiment is a deionized aqueous solution with a concentration of 20 mg / mL, calculated as calcium ions. The dropping rate of the calcium chloride dihydrate aqueous solution of this embodiment is 2.5 mL / min. The mass ratio of the added calcium ions to the added pectin of this embodiment is 0.07, and the crosslinking time is 10 min to form a shell layer.

[0092] B4. The obtained core-shell microcapsule dispersion was centrifuged. In this embodiment, the relative centrifugal force was 4000g, the centrifugation time was 8min, and the centrifugation temperature was 20℃. The precipitate was collected to obtain wet core-shell microcapsules. The wet core-shell microcapsules of this embodiment were resuspended in deionized water and washed once. The volume of deionized water used for each wash was 4 times the volume of the wet core-shell microcapsules of this embodiment. After washing, centrifugation was performed again. The precipitate was collected and resuspended in deionized water to obtain intermediate B (core-shell microcapsule dispersion). The particle size of the core-shell microcapsules in this embodiment was 10μm.

[0093] The preparation method of the antioxidant jam in this embodiment includes the following steps: S1, providing intermediate AP. S2, providing intermediate B. S3, mixing 25.00 parts of raspberry granules, 15.00 parts of blackberry pulp, 48.00 parts of sucrose, and deionized water, heating to 70°C, maintaining for 10 minutes, and then performing vacuum concentration; the absolute pressure of vacuum concentration in this embodiment is 0.025 MPa, the temperature of vacuum concentration in this embodiment is 60°C, and the endpoint of vacuum concentration in this embodiment is: the soluble solids content of the material is 35°Bx, measured by a refractometer at 20°C; after vacuum concentration in this embodiment, degassing is performed under reduced pressure for 3 minutes.

[0094] S4. After cooling the material obtained in step S3 to 45°C, the mixing in this embodiment is performed by shear dispersion. The rotation speed of shear dispersion in this embodiment is 2500 rpm. The shear dispersion in this embodiment is performed using a high-speed shear emulsifier. First, add intermediate AP of this embodiment and mix, then add intermediate B of this embodiment and mix, and mix for 10 min. The total amount of calcium ions added in this embodiment is 0.08 parts, which only includes the calcium ions introduced by intermediate A and intermediate B. No additional calcium salt needs to be added. Under stirring conditions, add 0.25 parts of citric acid to gradually adjust the pH value of the system to 3.4. The amount of citric acid added in this embodiment is counted as the mass of citric acid.

[0095] S5, the material obtained in step S4 is filled, sealed, and heat-treated. In this embodiment, the heat treatment temperature is 88°C, and the heat treatment time is 15 minutes, resulting in the antioxidant jam of this embodiment. In this embodiment, the filling is cold filling followed by heat treatment.

[0096] The total ascorbic acid content in the final antioxidant jam of this embodiment is 180 mg / kg. The ascorbic acid retention rate of the final antioxidant jam of this embodiment was determined after 30 days of sealed storage at 25°C in the dark. The retention rate in this embodiment was calculated as (ascorbic acid content on day 30 / initial ascorbic acid content) × 100%, where the initial ascorbic acid content was the total ascorbic acid content measured after cooling to 25°C following the heat treatment in step S5. The ascorbic acid retention rate of the final antioxidant jam of this embodiment was 64% after 30 days of sealed storage at 25°C in the dark.

[0097] The encapsulation efficiency of the core-shell microcapsules in this embodiment is 73%. The encapsulation efficiency was determined by the following method: The core-shell microcapsules of this embodiment were dispersed at a solid content of 3.0 wt% in 0.05 mol / L phosphate buffer solution with a pH of 7.0. After standing at 25°C for 30 min, the mixture was centrifuged to obtain the supernatant and precipitate. The centrifugation force in this embodiment was 5000 g, the centrifugation time was 5 min, and the centrifugation temperature was 25°C. The free ascorbic acid content in the supernatant of this embodiment was measured. The acid content and the total ascorbic acid content in the precipitate of this embodiment were determined. The total ascorbic acid content of the precipitate in this embodiment was determined after crushing. The sample used to determine the total ascorbic acid content in this embodiment was crushed using a high-speed homogenizer with a homogenization speed of 12000 rpm and a homogenization time of 2 min. The encapsulation efficiency in this embodiment is equal to the difference between the total ascorbic acid content and the free ascorbic acid content, divided by the total ascorbic acid content and multiplied by 100%. The free ascorbic acid content and the total ascorbic acid content in this embodiment were both determined by liquid chromatography.

[0098] The antioxidant activity of the antioxidant jam in this embodiment was evaluated by measuring its DPPH free radical scavenging ability. The antioxidant activity of the antioxidant jam in this embodiment was expressed as the DPPH free radical scavenging rate, which was determined as follows: a 0.10 mmol / L DPPH ethanol solution was prepared, and the sample was diluted with deionized water at a mass ratio of 1:20 and then mixed with the DPPH solution at a volume ratio of 1:1. The mixture was reacted at 25°C in the dark for 30 min, and the absorbance was measured at 517 nm. The scavenging rate was calculated as 1 - (A sample / A blank) × 100%. The DPPH free radical scavenging rate in this embodiment was 35%.

[0099] Features of the scheme in Example 3: This embodiment uses a traditional high-sucrose formulation: 40.00 parts fruit raw material, 48.00 parts sucrose, 0.60 parts intermediate AP, 1.50 parts intermediate B, 0.08 parts calcium ions, 0.25 parts citric acid, pH 3.4, ascorbic acid content 180 mg / kg, 30-day retention rate 64%, encapsulation rate 73%, DPPH scavenging rate 35%. Intermediate AP is in dry powder form with 5.0 wt% moisture; intermediate B is in dispersion form with microgel particle size of 400 nm and core-shell microcapsule particle size of 10 μm. Process parameters: pectin concentration 0.80 wt%, preparation temperature 20-25℃, shear speed 2500 rpm, calcium ion / pectin mass ratio 0.05-0.07, heat treatment at 88℃ for 15 min, concentrated to 35°Bx. This formulation emphasizes a traditional sweet taste and is suitable for use as a spread on traditional breakfast bread, cake filling, dessert decoration, and in home baking.

[0100] Example 4: Validation of Antioxidant Jam Formula with Diverse Process Parameters This embodiment provides an antioxidant jam, comprising the following components by weight: 25.00 parts apple puree, 13.00 parts pear puree, 50.00 parts sucrose, 0.70 parts citric acid, 0.25 parts trisodium citrate dihydrate, and a total calcium ion addition of 0.22 parts. The calcium ion sources in this embodiment include calcium ions introduced by intermediate A, calcium ions introduced by intermediate B, and calcium ions introduced by supplementary calcium chloride dihydrate and calcium lactate. The amount of calcium chloride dihydrate added in this embodiment is 0.08 parts, the amount of calcium lactate added is 0.12 parts, intermediate AP is 2.20 parts (based on dry solids, deducting the equivalent mass of calcium ions contained therein), intermediate BP is 4.50 parts (based on dry solids, deducting the equivalent mass of calcium ions contained therein), and deionized water is 4.13 parts (including intermediate AP and intermediate BP). The residual moisture and separately added deionized water are used to make the total mass of the above components 100 parts. In this embodiment, the total mass of fruit raw materials and sucrose is 38.00 + 50.00 = 88.00 parts, which does not exceed 91.15 parts. The pH value of the antioxidant jam in this embodiment is 2.9.

[0101] In this embodiment, intermediate AP is obtained by drying a pectin-calcium ion microgel dispersion after solid-liquid separation. The pectin-calcium ion microgel dispersion is obtained by forming an ionic cross-linking network between pectin and calcium ions at a pH of 3.3 and then dispersing it by shearing. The particle size of the microgel particles in the pectin-calcium ion microgel dispersion is 100 nm. The particle size in this embodiment is the Z-mean hydrated particle size measured by dynamic light scattering method. The dynamic light scattering method is used for measurement at a test temperature of 25 °C. The sample is diluted with deionized water to a solid content of 0.09 wt% before measurement.

[0102] In this embodiment, intermediate BP is prepared by drying a core-shell microcapsule dispersion after solid-liquid separation. The core-shell microcapsules comprise a core and a shell. The core contains ascorbic acid, and the shell contains an ionic cross-linked network formed by pectin and calcium ions. The particle size of the core-shell microcapsules in this embodiment is 45 μm. The particle size is the median diameter (D50) of the volume distribution, measured using a laser particle size analyzer at 25°C. The sample was diluted with deionized water to a solid content of 0.9 wt% before measurement. In this embodiment, intermediate A is dried after solid-liquid separation to obtain intermediate AP, and intermediate B is dried after solid-liquid separation to obtain intermediate BP.

[0103] Intermediate AP in this embodiment is prepared by the following steps: First, intermediate A is prepared, including the following steps: A1, low-methoxyl pectin is added to deionized water to prepare a pectin aqueous solution. The pectin aqueous solution in this embodiment has a pectin mass fraction of 1.80 wt%, and the degree of esterification of the low-methoxyl pectin in this embodiment is 33%. Mechanical stirring is carried out at 25°C, the stirring speed is 1000 rpm, and the stirring time is 150 min. Citric acid is added under stirring conditions. In this embodiment, citric acid is added in solid form in portions and the pH is measured in real time. The amount of citric acid added in this embodiment is 1.5 wt% of the dry basis mass of the pectin in this embodiment. The pH value of the pectin aqueous solution in this embodiment is gradually adjusted to 3.3, and the pH value is measured at 25°C.

[0104] A2. Under normal pressure and at a temperature of 12°C, the pectin aqueous solution of this embodiment was sheared and dispersed at a rotation speed of 7000 rpm, while calcium chloride dihydrate aqueous solution was added dropwise. The calcium chloride dihydrate aqueous solution of this embodiment was a deionized aqueous solution with a concentration of 45 mg / mL, calculated as calcium ions. The dropping rate of the calcium chloride dihydrate aqueous solution of this embodiment was 8.5 mL / min. The mass ratio of the added calcium ions to the pectin of this embodiment was 0.13, where the mass of the pectin of this embodiment was the dry basis mass of the added pectin. The shearing and dispersion time was 25 min.

[0105] A3, when the mass ratio of the added calcium ions to the pectin in this embodiment reaches 0.13, stop adding the solution and continue shearing and dispersing for 12 minutes.

[0106] A4. The obtained dispersion is filtered through a sieve with a pore size of 150 μm, and the filtrate is collected to obtain intermediate A; wherein, the solid content of intermediate A in this embodiment is 2.30 wt%, and the particle size of the microgel particles in this embodiment is 100 nm.

[0107] The intermediate AP in this embodiment is further prepared by the following steps: C1, the intermediate A obtained above is centrifuged. The relative centrifugal force for centrifugation in this embodiment is 9000g, and the centrifugation time is 25min, to obtain a wet microgel. C2, the wet microgel of this embodiment is dried at an absolute pressure of 0.008MPa and a temperature of 55°C for 18h to obtain intermediate AP; wherein, the water content of intermediate AP in this embodiment is 1.5wt%.

[0108] Intermediate BP of this embodiment is prepared by the following steps: First, intermediate B is prepared, including the following steps: B1, ascorbic acid is dissolved in deionized water to obtain an ascorbic acid aqueous solution, wherein the mass fraction of ascorbic acid in the ascorbic acid aqueous solution of this embodiment is 27.0 wt%; low-methoxyl pectin is added to the ascorbic acid aqueous solution of this embodiment, so that the mass ratio of pectin to ascorbic acid in this embodiment is 0.085, wherein the degree of esterification of the low-methoxyl pectin in this embodiment is 33%; the low-methoxyl pectin in this embodiment is dissolved by mechanical stirring at 25°C, the stirring speed is 1000 rpm, and the stirring time is 150 min; after the low-methoxyl pectin in this embodiment is dissolved under stirring conditions, citric acid is added. In this embodiment, the citric acid is added in solid form in portions and the pH is measured in real time. The amount of citric acid added in this embodiment is 1.5 wt% of the dry basis mass of the pectin in this embodiment. The pH value of the system is gradually adjusted to 2.9, and the pH value is measured at 25°C.

[0109] B2. Under normal pressure and at a temperature of 8°C, the system of this embodiment was sheared and dispersed at a rotation speed of 7000 rpm while calcium chloride dihydrate aqueous solution was added dropwise. The calcium chloride dihydrate aqueous solution in this embodiment was a deionized aqueous solution with a concentration of 45 mg / mL, calculated as calcium ions. The dropping rate of the calcium chloride dihydrate aqueous solution in this embodiment was 8.5 mL / min. The mass ratio of the added calcium ions to the pectin in this embodiment was 0.18, where the mass of the pectin in this embodiment was the dry basis mass of the added pectin. The shearing and dispersion time was 25 min, resulting in a gel core particle dispersion containing ascorbic acid.

[0110] B3. Preparation of pectin aqueous solution: Low-methoxyl pectin was added to deionized water and mechanically stirred at 1000 rpm for 100 min at 25°C until no visible agglomerates were observed. The pH of the pectin aqueous solution in this example was adjusted dropwise to 6.3 using 1.0 mol / L sodium hydroxide aqueous solution. The pH value was directly measured at 25°C using a calibrated pH meter. The solution was stirred until homogeneous and transparent to obtain a pectin aqueous solution. The mass fraction of pectin in the pectin aqueous solution of this example was 1.80 wt%, and the pH value of the pectin aqueous solution in this example was 6.3. [The text then abruptly shifts to a seemingly unrelated topic:] ...to the ascorbic acid-containing... The pectin aqueous solution of this embodiment is added to the gel core particle dispersion, so that the mass ratio of the added pectin on a dry basis to the pectin in the gel core particle dispersion containing ascorbic acid of this embodiment on a dry basis is 0.45; calcium chloride dihydrate aqueous solution is added dropwise again. The calcium chloride dihydrate aqueous solution of this embodiment is a deionized aqueous solution with a concentration of 45 mg / mL and is calculated as calcium ions. The dropping rate of the calcium chloride dihydrate aqueous solution of this embodiment is 8.5 mL / min; so that the mass ratio of the added calcium ions to the added pectin of this embodiment is 0.18, and the crosslinking time is 25 min, to form a shell layer.

[0111] B4. The obtained core-shell microcapsule dispersion was centrifuged. In this embodiment, the relative centrifugal force was 7000g, the centrifugation time was 18min, and the centrifugation temperature was 8℃. The precipitate was collected to obtain wet core-shell microcapsules. The wet core-shell microcapsules of this embodiment were resuspended in deionized water and washed three times. The volume of deionized water used for each wash was 8 times the volume of the wet core-shell microcapsules of this embodiment. After washing, centrifugation was performed again. The precipitate was collected and resuspended in deionized water to obtain intermediate B (core-shell microcapsule dispersion). The particle size of the core-shell microcapsules in this embodiment was 45μm.

[0112] The intermediate BP of this embodiment is further prepared by the following steps: D1, the intermediate B obtained above is centrifuged. The relative centrifugal force for centrifugation in this embodiment is 7000g, and the centrifugation time is 25min, to obtain wet core-shell microcapsules. D2, the wet core-shell microcapsules of this embodiment are dried at an absolute pressure of 0.008MPa and a temperature of 50°C for 20h to obtain intermediate BP; wherein, the water content of intermediate BP in this embodiment is 1.2wt%.

[0113] The preparation method of the antioxidant jam in this embodiment includes the following steps: S1, providing intermediate AP. S2, providing intermediate BP. S3, mixing 25.00 parts of apple puree, 13.00 parts of pear puree, 50.00 parts of sucrose, and deionized water, heating to 90°C, maintaining for 25 minutes, and then performing vacuum concentration; the absolute pressure of vacuum concentration in this embodiment is 0.055 MPa, the temperature of vacuum concentration in this embodiment is 72°C, and the endpoint of vacuum concentration in this embodiment is: the soluble solids content of the material is 63°Bx, measured by a refractometer at 20°C; after vacuum concentration in this embodiment, degassing is performed under reduced pressure for 8 minutes.

[0114] S4. After cooling the material obtained in step S3 to 60°C, the mixing in this embodiment is performed by shear dispersion. The shear dispersion speed in this embodiment is 7000 rpm. The shear dispersion in this embodiment is performed using a homogenizer. First, add intermediate AP of this embodiment and mix, then add intermediate BP of this embodiment and mix, mixing for 25 minutes. If necessary, add 0.08 parts of calcium chloride dihydrate and 0.12 parts of calcium lactate to make the total amount of calcium ions added in the final antioxidant jam 0.22 parts in terms of calcium ions. The total amount of calcium ions added in this embodiment includes calcium ions introduced by intermediate A, calcium ions introduced by intermediate B, and calcium ions introduced by the added calcium chloride dihydrate and calcium lactate. Under stirring conditions, add 0.70 parts of citric acid and 0.25 parts of trisodium citrate dihydrate to gradually adjust the pH value of the system to 2.9. The amount of citric acid added in this embodiment is counted as the mass fraction of citric acid.

[0115] S5, the material obtained in step S4 is filled, sealed, and heat-treated. In this embodiment, the heat treatment temperature is 92°C, and the heat treatment time is 28 minutes, resulting in the antioxidant jam of this embodiment. In this embodiment, the filling is cold filling followed by heat treatment.

[0116] The total ascorbic acid content in the final antioxidant jam of this embodiment is 480 mg / kg. The ascorbic acid retention rate of the final antioxidant jam of this embodiment was determined after 30 days of sealed storage at 25°C in the dark. The retention rate in this embodiment was calculated as (ascorbic acid content on day 30 / initial ascorbic acid content) × 100%, where the initial ascorbic acid content was the total ascorbic acid content measured after cooling to 25°C following the heat treatment in step S5. The ascorbic acid retention rate of the final antioxidant jam of this embodiment was 75% after 30 days of sealed storage at 25°C in the dark.

[0117] The encapsulation efficiency of the core-shell microcapsules in this embodiment is 85%. The encapsulation efficiency was determined by the following method: The core-shell microcapsules of this embodiment were dispersed at a solid content of 8.0 wt% in 0.05 mol / L phosphate buffer solution with a pH of 7.0. After standing at 25°C for 30 min, the mixture was centrifuged to obtain the supernatant and precipitate. The centrifugation force in this embodiment was 5000 g, the centrifugation time was 5 min, and the centrifugation temperature was 25°C. The free ascorbic acid content in the supernatant of this embodiment was measured. The acid content and the total ascorbic acid content in the precipitate of this embodiment were determined. The total ascorbic acid content of the precipitate in this embodiment was determined after crushing. The sample used to determine the total ascorbic acid content in this embodiment was crushed using a high-speed homogenizer with a homogenization speed of 20,000 rpm and a homogenization time of 5 min. The encapsulation efficiency in this embodiment was equal to the difference between the total ascorbic acid content and the free ascorbic acid content, divided by the total ascorbic acid content and multiplied by 100%. The free ascorbic acid content and the total ascorbic acid content in this embodiment were both determined by liquid chromatography.

[0118] The antioxidant activity of the antioxidant jam in this embodiment was evaluated by measuring its DPPH free radical scavenging ability. The antioxidant activity of the antioxidant jam in this embodiment was expressed as the DPPH free radical scavenging rate, which was determined as follows: a 0.10 mmol / L DPPH ethanol solution was prepared, and the sample was diluted with deionized water at a mass ratio of 1:20 and then mixed with the DPPH solution at a volume ratio of 1:1. The mixture was reacted at 25°C in the dark for 30 min, and the absorbance was measured at 517 nm. The scavenging rate was calculated as 1 - (A sample / A blank) × 100%. The DPPH free radical scavenging rate in this embodiment was 52%.

[0119] Example 4 demonstrates the feasibility of high-level parameter combinations, applicable to scenarios such as health care foods, nutritional supplements for the elderly, energy supplements for athletes, special dietary products, and high-end gift jams.

[0120] Comparative Example 1: It is basically the same as Example 1, except that the total amount of calcium ions added is 0.01 parts, the amount of deionized water is adjusted accordingly to make the total mass parts 100 parts, and the amounts of other components and preparation conditions remain unchanged.

[0121] Comparative Example 2: It is basically the same as Example 1, except that the total amount of calcium ions added is 0.30 parts, the amount of deionized water is adjusted accordingly to make the total mass parts 100 parts, and the amounts of other components and preparation conditions remain unchanged.

[0122] Comparative Example 3: It is basically the same as Example 1, except that the microgel particles of the pectin-calcium ion microgel dispersion in intermediate A have a particle size of 50 nm, while the amount of other components and preparation conditions remain unchanged.

[0123] Comparative Example 4: It is basically the same as Example 1, except that the particle size of the core-shell microcapsules in intermediate B is 65 μm, while the amount of other components and preparation conditions remain unchanged.

[0124] Comparative Example 5: It is basically the same as Example 1, except that the pH value of the antioxidant jam is 2.5, the amount of citric acid is adjusted accordingly and included in the mass fraction of citric acid, the amount of deionized water is adjusted accordingly so that the total mass fraction is 100 parts, and the amounts of other components and preparation conditions remain unchanged.

[0125] Comparative Example 6: It is basically the same as Example 1, except that intermediate AP is not added, the amount of intermediate AP is changed to 0 parts, the amounts of other components are adjusted proportionally to make the total mass parts 100 parts, and other preparation conditions remain unchanged.

[0126] Comparative Example 7: Basically the same as Example 1, except that intermediate B is not added, the amount of intermediate B is changed to 0 parts, the amounts of other components are adjusted proportionally to make the total mass parts 100 parts, and other preparation conditions remain unchanged.

[0127] Comparative Example 8: It is basically the same as Example 1, except that the amount of sucrose is 60.00 parts, the amount of fruit raw material is adjusted to 27.50 parts so that the total mass of fruit raw material and sucrose does not exceed 91.45 parts, the amount of other components is adjusted proportionally so that the total mass is 100 parts, and other preparation conditions remain unchanged.

[0128] Performance testing: Experiment 1: Determination of DPPH free radical scavenging ability Test Subject: Antioxidant jam sample. Test Objective: To evaluate the antioxidant activity of the jam and characterize the antioxidant function of microencapsulated ascorbic acid in the jam system. Test Principle: DPPH free radicals are stable organic free radicals with maximum absorption at 517 nm. Antioxidants can reduce DPPH free radicals through hydrogen atom or electron transfer, leading to a decrease in absorbance. The degree of decrease is proportional to the antioxidant capacity. Experimental Method: Prepare a 0.10 mmol / L DPPH ethanol solution. Dilute the jam sample with deionized water at a mass ratio of 1:20 and mix it with the DPPH solution at a volume ratio of 1:1. React at 25℃ in the dark for 30 min. Measure the absorbance at 517 nm using a UV-Vis spectrophotometer. Use deionized water as a blank control. Key Parameters: Reaction temperature 25±1℃, reaction time 30 min, wavelength 517 nm, sample dilution factor 20-fold. Data processing: The clearance rate is calculated using the formula: DPPH clearance rate (%) = [1 - (A sample / A blank)] × 100%. Each sample is measured in parallel 3 times and the average value is taken.

[0129] Experiment 2: Ascorbic acid retention rate determination (30-day storage stability) Test Subject: Sealed packaged antioxidant jam samples. Test Objective: To evaluate the protective effect of the microencapsulation system on ascorbic acid during storage and verify shelf-life stability. Test Principle: Ascorbic acid degrades during storage due to oxidation, light, and temperature. The protective effect of the encapsulation is assessed by measuring the change in ascorbic acid content before and after storage. Experimental Method: Jam samples were sealed and stored in a light-protected incubator at 25±2℃ for 30 days. Samples were taken on day 0 (after cooling to 25℃ following heat treatment) and day 30. The ascorbic acid content was determined by high-performance liquid chromatography (HPLC). The chromatographic conditions were: C18 column, mobile phase: 0.1% phosphoric acid aqueous solution, flow rate: 1.0 mL / min, detection wavelength: 245 nm. Key Parameters: Storage temperature 25±2℃, storage time 30 days, light-protected and sealed conditions, HPLC detection wavelength 245 nm. Data processing: The retention rate is calculated using the formula: Retention rate (%) = (Ascorbic acid content on day 30 / Initial ascorbic acid content) × 100%. Each sample is measured in parallel 3 times and the average value is taken.

[0130] Experiment 3: Determination of Microcapsule Encapsulation Efficiency Test subject: Intermediate B (core-shell microcapsules). Test objective: To evaluate the encapsulation efficiency of core-shell microcapsules against ascorbic acid and verify shell integrity. Test principle: Under neutral pH conditions, the pectin-calcium ion cross-linked network structure is stable, allowing free ascorbic acid to be released into the supernatant, while the encapsulated ascorbic acid is mainly retained inside the microcapsules. By measuring the free ascorbic acid content in the supernatant and separately measuring the total ascorbic acid content in an equal volume of core-shell microcapsule dispersion as used before centrifugation, the encapsulation efficiency can be calculated. Experimental Methods: Core-shell microcapsules were dispersed at a solid content of 5.0 wt% in 0.05 mol / L phosphate buffer (pH 7.0). After standing at 25°C for 30 min, the microcapsules were centrifuged at 5000 g for 5 min. The supernatant was collected to determine the free ascorbic acid content. Separately, an equal volume of the core-shell microcapsule dispersion was homogenized using a high-speed homogenizer (15000 rpm, 3 min) to determine the total ascorbic acid content. Both methods were performed using HPLC. Standard Basis: Refer to the general method for determining microcapsule encapsulation efficiency. Key Parameters: pH 7.0, standing temperature 25°C, centrifugation force 5000 g, homogenization speed 15000 rpm. Data Processing: Encapsulation efficiency (%) = [(total content - free content) / total content] × 100%, with three parallel determinations.

[0131] Experiment 4: Apparent Viscosity Measurement Test Subject: Finished antioxidant jam. Test Objective: To evaluate the rheological properties and processability of the jam, and to verify the viscosity control effect after the introduction of microgels / microcapsules. Test Principle: Jam is a non-Newtonian fluid, and its apparent viscosity changes with shear rate. Viscosity was measured at different shear rates using a rotational rheometer to evaluate flowability and spreadability. Experimental Method: Jam samples were placed on a test stage with a 1mm gap between the plates of the rotational rheometer. Shear rate scanning was performed at 25±1℃, with a shear rate range of 0.1-100s. -1 Record the change in apparent viscosity with shear rate, selecting 50 s. -1 The apparent viscosity at the shear rate is used as the characteristic viscosity value. Key parameters: test temperature 25±1℃, gap 1mm, shear rate range 0.1-100s. -1 Characteristic shear rate 50s -1 Data processing: Record for 50 seconds. -1 The apparent viscosity value (Pa·s) of each sample was measured in triplicate and the average value was taken.

[0132] Experiment 5: Determination of water separation rate (shelf stability) Test Subject: Sealed packaged antioxidant jam samples. Test Objective: To evaluate the structural stability and water separation ability of the jam during storage, and to verify the synergistic stabilizing effect of the double-layer calcium cross-linked network. Test Principle: During storage, water may be released from the jam due to gel network shrinkage; a lower water separation rate indicates a more stable structure. Experimental Method: The jam samples were sealed and stored in a constant temperature incubator at 25±2℃ for 30 days, protected from light. The initial mass m0 was weighed before storage. After 30 days, the container was opened, tilted at 45°, and allowed to stand for 30 minutes. The released free water was collected and weighed as m1, and the remaining jam was weighed as m2. Standard Basis: Refer to the general method for determining water separation rate in the jam industry. Key Parameters: Storage temperature 25±2℃, storage time 30 days, tilt angle 45°, standing time 30 minutes. Data Processing: Water separation rate (%) = (m1 / m0) × 100%, mass conservation verification m0 = m1 + m2, each sample was measured in triplicate.

[0133] Experiment 6: Determination of total ascorbic acid content Test Subject: Finished antioxidant jam. Test Objective: To quantitatively determine the total ascorbic acid content in the jam and verify the microcapsule loading efficiency and the functionality of the formulation design. Test Principle: Ascorbic acid has strong reducing properties and can be accurately quantified by high-performance liquid chromatography (HPLC) under acidic conditions. Encapsulated and free ascorbic acid can be completely released and measured after sample disruption. Experimental Method: Accurately weigh 2.00 g of jam sample into a 50 mL volumetric flask, add 30 mL of extraction solution containing 2% metaphosphoric acid, and thoroughly extract using a high-speed homogenizer (10000 rpm, 5 min). After dilution to volume, filter through a 0.45 μm filter membrane. Analyze the filtrate using HPLC. Chromatographic conditions: C18 column (250 mm × 4.6 mm, 5 μm), mobile phase: 0.1% phosphoric acid aqueous solution, flow rate: 1.0 mL / min, column temperature: 30℃, detection wavelength: 245 nm, injection volume: 10 μL. Key parameters: Extraction solution 2% metaphosphoric acid, crushing speed 10000 rpm, HPLC wavelength 245 nm, column temperature 30℃. Data processing: Content (mg / kg) was calculated according to the standard curve, and the determination was performed in triplicate.

[0134] Figure 1 The XRD / XRPD spectra of Examples 1, 6, and 7 are compared. X-ray diffraction characterization was used, with the basic parameters being the horizontal axis representing the 2θ angle range of approximately 5 to 40 degrees and the vertical axis representing relative intensity; the variable parameter was the difference in the sample formulation system. The results show that Example 1 exhibits clearer and stronger peaks and a more stable background morphology in the characteristic diffraction range, while the peaks of Comparative Examples 6 and 7 are weaker and more diffuse, indicating that this scheme forms a more ordered solid-phase structure or a more stable inorganic-organic synergistic assembly state, supporting the rationality of the system construction from a structural perspective.

[0135] Figure 2 The following are comparative FTIR spectra of Example 1, Comparative Example 1, and Comparative Example 2, characterized by Fourier transform infrared spectroscopy. The basic parameters are: abscissa wavenumber range of approximately 4000 to 600 cm⁻¹. -1 The samples are arranged from highest to lowest absorbance, with the vertical axis representing absorbance. The variable parameters are differences in calcium-related conditions and formulation systems in the samples. The results show that Example 1 exhibits a more matched peak shape and relative intensity combination in the carboxyl-related absorption region and the broad peak region of hydroxyl groups. The related peak shapes of Comparative Example 1 and Comparative Example 2 show different degrees of imbalance, indicating that this scheme achieves a more reasonable synergy between ionic crosslinking and hydrogen bonding networks, supporting the correctness of the structural design from the perspective of chemical interaction.

[0136] Figure 3The laser particle size distribution / differential volumetric distribution plots for Examples 1, 3, and 4 are shown. Laser particle size analysis was used for characterization. The basic parameters are: x-axis representing particle size range of approximately 0.5 to 200 μm on a logarithmic scale, and y-axis representing volumetric density. The variable parameters are the differences in particle size distribution between the sample formulation and the formed particles. The results show that the differential distribution in Example 1 is more concentrated and the main peak is more distinct, while Comparative Example 3 exhibits a wider distribution or multi-peak characteristics, and Comparative Example 4 is biased towards a coarser particle region. This indicates that the proposed method can more effectively control particle formation and aggregation, resulting in higher particle size uniformity, thus providing a foundation for subsequent stability and controllable release.

[0137] Figure 4 The laser particle size distribution / cumulative volume distribution curves for Examples 1, 3, and 4 are shown below. Laser particle size analysis was used for characterization. The basic parameters are: the x-axis represents the particle size range of approximately 0.5 to 200 μm on a logarithmic scale; the y-axis represents the cumulative volume distribution percentage from 0 to 100. The variable parameter is the difference in quantile particle sizes (D10, D50, D90) caused by the sample formulation. The results show that the cumulative curve for Example 1 is steeper and the transition is more concentrated near the median particle size. The cumulative transitions for Comparative Examples 3 and 4 are smoother or shift towards the coarser particle end, indicating that this scheme has a narrower particle population distribution and stronger batch-to-batch controllability, reflecting the rationality of the process and system selection.

[0138] Figure 5 The cumulative release curves (pH 2.0) of ascorbic acid for Example 1 and Comparative Example 5 are shown in the figure. In vitro release experiments were used for characterization. The baseline parameters were time (0-72 h) on the x-axis and cumulative release rate (0-100) on the y-axis. The variable parameters were the difference between the medium pH 2.0 and the sample system. The results show that both exhibited a relatively rapid release trend under strong acid conditions, but the curve for Example 1 was smoother and the release process was more predictable. Comparative Example 5 showed a steeper release increase or approached the plateau earlier, indicating that this scheme can still provide a certain structural sustained-release contribution under harsh conditions, supporting the effectiveness of its stabilization strategy.

[0139] Figure 6 The graph shows the cumulative release curves (pH 3.0) of ascorbic acid for Example 1 and Comparative Example 5. In vitro release experiments were used for characterization. The baseline parameters were time (0-72 h) on the x-axis and cumulative release rate (0-100) on the y-axis. The variable parameter was the difference between the medium pH 3.0 and the sample system. The results show that Example 1 released more slowly and more closely resembled sustained release behavior, while Comparative Example 5 released more quickly. This indicates that the proposed method can more effectively suppress the initial burst release and prolong the release process in a weakly acidic environment, functionally demonstrating the rationality of the synergistic effect of core-shell and cross-linking on controlled release.

[0140] Figure 7The cumulative release curves (pH 4.0) of ascorbic acid for Example 1 and Comparative Example 5 are shown in the figure. In vitro release experiments were used for characterization. The baseline parameters were time (0-72 h) on the x-axis and cumulative release rate (0-100) on the y-axis. The variable parameter was the difference between the medium pH 4.0 and the sample system. The results show that Example 1 maintained a more stable release slope and a later plateau time under moderate acidity, while Comparative Example 5 showed an earlier and accelerated release. This indicates that this scheme is more conducive to sustained release and activity maintenance under conditions close to actual acidic food systems, demonstrating the applicability and rationality of the structural design.

[0141] Figure 8 The graph shows the cumulative release curves (pH 7.0) of ascorbic acid for Example 1 and Comparative Example 5. In vitro release experiments were used for characterization. The baseline parameters were time (0-72 h) on the x-axis and cumulative release rate (0-100) on the y-axis. The variable parameters were the difference between the medium pH 7.0 and the sample system. The results show that both Example 1 and Comparative Example 5 can release ascorbic acid, but the release curve of Example 1 is more controllable and the overall release process is more balanced. This indicates that this method can still achieve stable release behavior under neutral conditions through structural barrier and diffusion path regulation, thus supporting its rationality for cross-environmental adaptability.

[0142] Figure 9 The image shows the macroscopic morphology of the antioxidant jam prepared in Example 1. It illustrates the deep red to purplish-red hue dominated by natural strawberry and blueberry pigments at pH 3.2, and the overall turbidity and opacity resulting from light scattering caused by intermediate A (pectin microgel) and intermediate B (core-shell microcapsules). This image demonstrates that the multi-scale dispersed phases are uniformly dispersed within the jam matrix, forming a macroscopic system with uniform color and a typical semi-gloss finish.

[0143] Figure 10 shows a scanning electron microscope (SEM) image of the dried antioxidant jam sample from Example 1. The basic parameters are that the sample originated from Example 1, and the surface and cross-section of the sample were observed using an SEM. As can be seen from the 200 μm scale bar in the figure, the sample exhibits a continuous porous matrix structure with a large number of near-spherical micron-sized particles distributed within the matrix. This figure mainly reflects the microscopic morphology of the dried sample and the distribution of particles in the matrix. Since the scale of this figure is at the micron level, it cannot be directly concluded that surface particles of 100-200 nm exist, nor should it be used as direct evidence of the particle size of nanogels in the hydrated state.

[0144] Figure 11This is a transmission electron microscope (TEM) image of an ultrathin section of the shell / core structure of the core-shell microcapsule in Example 1. This image utilizes ultrathin sectioning as a fundamental parameter-based method, overcoming the limitation of direct electron imaging for micron-sized particles. The image clearly reveals the variable parameter: the microcapsule possesses a continuous, dense pectin-calcium cross-linked shell ring, effectively encapsulating the internal core layer. The shell thickness uniformity is good, and the interface structure is clear, intuitively demonstrating the correctness of the interfacial cross-linking strategy for preparing microcapsules with a stable core-shell structure.

[0145] Table 1 Performance summary of examples and comparative examples

[0146] Note: The "encapsulation efficiency (%)" was determined according to the method in Experiment 3; samples without intermediate B were marked with "—". As can be seen from the performance of the examples and comparative examples in Table 1, the four examples are generally superior to the corresponding comparative examples in terms of DPPH free radical scavenging rate, 30-day retention rate, encapsulation rate, and water separation rate, verifying the effectiveness of the technical solution of the present invention. Comparative Example 1, with a total calcium ion content of only 0.01 parts, far below the lower limit of 0.02 parts in the technical solution, resulted in insufficient calcium cross-linking network strength, leading to an encapsulation rate of only 52%, a retention rate of only 48%, and a water separation rate as high as 8.5%. This indicates that insufficient calcium ion content seriously affects the stability of the microcapsules and the antioxidant protection effect. Comparative Example 2, with a total calcium ion content of 0.30 parts, exceeded the upper limit of 0.25 parts. Although the encapsulation rate was improved, excessive cross-linking led to a significant increase in viscosity to 18.5 Pa·s, and the water separation rate of 6.2% was still higher than that of the examples. This indicates that excessive calcium ions caused the gel network to become too tight, which in turn affected the system's balance. Comparative Examples 3 and 4 deviated from the optimal particle size range due to the microgel particle size of 50 nm being too small and the core-shell microcapsule particle size of 65 μm being too large, resulting in decreased dispersion stability and reduced encapsulation efficiency, with retention rates of only 58% and 55%, respectively. This indicates that particle size control is crucial for microcapsule function. Comparative Example 5, with a pH of 2.5, was below the lower limit of 2.8. Excessively low pH disrupted the stability of the pectin gel network, reducing the encapsulation efficiency to 58%, with a high water separation rate of 9.2% and a retention rate of only 42%, demonstrating the decisive role of pH optimization in system stability. Comparative Examples 6 and 7 lacked intermediates AP and B, respectively, leading to a sharp decline in antioxidant performance. DPPH scavenging rates were only 18% and 15%, with retention rates of only 35% and 32%, respectively. Ascorbic acid content decreased to 150 and 85 mg / kg, with high water separation rates of 12.5% ​​and 14.8%, fully demonstrating the indispensability of the bilayer microgel / microcapsule synergistic system for antioxidant function and structural stability. The sucrose content of Comparative Example 8 was 60 parts, exceeding the upper limit of 55 parts. Although the impact on antioxidant properties was relatively small, the viscosity increased to 22.5 Pa·s, which seriously affected processability and taste. This indicates that the amount of sucrose used needs to be strictly controlled within a reasonable range to balance functionality and processability.

[0147] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit it. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that any equivalent structural transformations made under the concept of the present invention and using the contents of the specification and drawings of the present invention should be covered within the scope of protection of the claims of the present invention.

Claims

1. An antioxidant jam, characterized in that, The following components are included by mass: Fruit raw materials: 35.00-70.00 parts, wherein the fruit raw materials are in the form of one or more of the following: pre-processed fruit slices, fruit pieces, fruit pulp, and fruit puree; Sucrose 15.00-55.00 parts; Citric acid 0.05-0.80 parts; The total amount of calcium ions added is 0.02-0.25 parts, based on calcium ions. The sources of calcium ions include calcium ions introduced by intermediate A, calcium ions introduced by intermediate B, and / or calcium ions introduced by supplementary calcium salts. The supplementary calcium salts are selected from one or both of calcium chloride dihydrate and calcium lactate. When the supplementary calcium salt is calcium chloride dihydrate, the amount of calcium chloride dihydrate added does not exceed 0.10 parts, based on calcium chloride dihydrate. Intermediate A, 0.10-2.50 parts, wherein the mass of intermediate A is based on dry solids and the equivalent mass of calcium ions contained therein is deducted. Pectin-calcium ion microgel is prepared by forming an ionic cross-linking network between pectin and calcium ions and then dispersing it by shearing. The pectin-calcium ion microgel is used in the form of a pectin-calcium ion microgel dispersion, or in the form of intermediate AP obtained by drying after solid-liquid separation. Intermediate B 0.05-5.00 parts, wherein the mass of intermediate B is based on dry solids and deducts the equivalent mass of calcium ions contained therein, and intermediate B is a core-shell microcapsule, wherein the core-shell microcapsule is used in the form of a core-shell microcapsule dispersion, or in the form of intermediate BP obtained by drying after solid-liquid separation, wherein the core-shell microcapsule comprises a core and a shell, wherein the core contains ascorbic acid or sodium ascorbate, and the shell contains an ionic crosslinking network formed by pectin and calcium ions; The remaining amount of deionized water makes the sum of the mass parts of the above components 100 parts, wherein the mass parts of deionized water include the water contained in intermediate A and / or intermediate B, the water introduced when intermediate A and / or intermediate B are used in dispersion form, the residual water of intermediate AP and / or intermediate BP, and additionally added deionized water; wherein the sum of the mass parts of fruit raw materials and sucrose does not exceed 91.45 parts. The antioxidant jam has a pH value of 2.8-3.

6.

2. The antioxidant jam according to claim 1, characterized in that, The pectin-calcium ion microgel dispersion in intermediate A is prepared by forming an ionic cross-linking network between pectin and calcium ions under conditions of pH 3.2-4.2 and then dispersing it by shearing. The particle size of the microgel particles in the pectin-calcium ion microgel dispersion is 80-500 nm. The particle size is the Z-mean hydrated particle size measured by dynamic light scattering method. The dynamic light scattering method is used for determination at a test temperature of 25℃. The sample is diluted with deionized water to a solid content of 0.01-0.10 wt% before determination. The core-shell microcapsules in intermediate B have a particle size of 1-50 μm. The particle size is the median diameter D50 of the volume distribution measured by a laser particle size analyzer. The test temperature is 25℃. The sample is diluted with deionized water to a solid content of 0.1-1.0 wt% before measurement. Intermediate A is used in the form of a pectin-calcium ion microgel dispersion, or in the form of intermediate AP obtained by drying after solid-liquid separation; Intermediate B is used in the form of a core-shell microcapsule dispersion, or in the form of intermediate BP obtained by drying after solid-liquid separation.

3. The antioxidant jam according to claim 1, characterized in that, The preparation method of intermediate A used in the antioxidant jam includes the following steps: A1. A pectin aqueous solution is prepared by adding low-methoxyl pectin to deionized water, wherein the pectin aqueous solution contains 0.50-2.00 wt% pectin and the degree of esterification of the low-methoxyl pectin is less than 50%; citric acid is added under stirring conditions, wherein the amount of citric acid added is 0.1-2.0 wt% of the dry weight of the pectin, and the pH value of the pectin aqueous solution is gradually adjusted to 3.2-4.2; A2, under normal pressure and at a temperature of 10-30℃, the pectin aqueous solution is sheared and dispersed at a rotation speed of 500-8000 rpm, while a calcium salt aqueous solution is added dropwise. The calcium salt aqueous solution is a deionized aqueous solution with a concentration of 10-50 mg / mL and is calculated as calcium ions. The dropping rate of the calcium salt aqueous solution is 0.5-10 mL / min. The mass ratio of the added calcium ions to the pectin is 0.02-0.15, where the mass of the pectin is the dry weight of the added pectin. The shearing and dispersion time is 5-30 min. A3, when the mass ratio of added calcium ions to the pectin reaches 0.02-0.15, stop adding the solution and continue shearing and dispersing for 3-15 minutes; A4. The obtained dispersion is filtered through a sieve with a pore size of 100-500 μm, and the filtrate is collected to obtain intermediate A; wherein the solid content of intermediate A is 0.60-2.50 wt%, and the particle size of the microgel particles is 80-500 nm.

4. The antioxidant jam according to claim 1, characterized in that, The preparation method of intermediate B used in the antioxidant jam includes the following steps: B1. Ascorbic acid or sodium ascorbate is dissolved in deionized water to obtain an aqueous solution of ascorbic acid or sodium ascorbate, wherein the mass fraction of ascorbic acid or sodium ascorbate in the aqueous solution is 5.0-30.0 wt%; low-methoxyl pectin is added to the aqueous solution of ascorbic acid or sodium ascorbate, such that the mass ratio of pectin to ascorbic acid or sodium ascorbate is 0.01-0.10, wherein the degree of esterification of the low-methoxyl pectin is less than 50%; after the low-methoxyl pectin is dissolved under stirring, citric acid is added, wherein the amount of citric acid added is 0.1-2.0 wt% of the dry basis mass of the pectin, and the pH value of the system is gradually adjusted to 2.8-3.6; B2, under normal pressure and at a temperature of 5-25℃, the system is sheared and dispersed at a rotation speed of 500-8000 rpm while a calcium salt aqueous solution is added dropwise. The calcium salt aqueous solution is a deionized aqueous solution with a concentration of 10-50 mg / mL and is calculated as calcium ions. The dropping rate of the calcium salt aqueous solution is 0.5-10 mL / min. The mass ratio of the added calcium ions to the pectin is 0.03-0.20, where the mass of the pectin is the dry weight of the added pectin. The shearing and dispersion time is 5-30 min, resulting in a gel core particle dispersion containing ascorbic acid. B3. Preparation of pectin aqueous solution: Add low-methoxyl pectin to deionized water and stir until uniform and transparent to obtain a pectin aqueous solution. The pectin aqueous solution has a pectin mass fraction of 0.50-2.00 wt% and a pH value of 5.0-6.

5. Add the pectin aqueous solution to the ascorbic acid-containing gel core particle dispersion, so that the mass ratio of the added pectin (dry basis) to the pectin in the ascorbic acid-containing gel core particle dispersion (dry basis) is 0.05-0.

50. Add calcium salt aqueous solution again. The calcium salt aqueous solution is a deionized aqueous solution with a concentration of 10-50 mg / mL and is calculated as calcium ions. The dropping rate of the calcium salt aqueous solution is 0.5-10 mL / min. The mass ratio of the added calcium ions to the added pectin is 0.03-0.

20. The cross-linking time is 5-30 min to form a shell layer. B4. The obtained core-shell microcapsule dispersion is centrifuged at a relative centrifugal force of 3000-8000g, a centrifugation time of 5-20min, and a centrifugation temperature of 4-25℃. The precipitate is collected to obtain wet core-shell microcapsules. The wet core-shell microcapsules are resuspended in deionized water and washed 1-3 times, with the volume of deionized water used in each wash being 3-10 times the volume of the wet core-shell microcapsules. After washing, centrifugation is performed again to obtain intermediate B. The particle size of the core-shell microcapsules is 1-50μm.

5. The antioxidant jam according to claim 3, characterized in that, Intermediate A used in the antioxidant jam is further prepared into intermediate AP, which is prepared through the following steps: C1, the intermediate A obtained in steps A1-A4 is centrifuged, the relative centrifugal force of which is 5000-10000g and the centrifugation time is 10-30min, to obtain wet microgel; C2, the wet microgel is dried at an absolute pressure of 0.005-0.030 MPa and a temperature of 40-60℃ for 6-24 h to obtain intermediate AP; wherein the water content of intermediate AP is 0.5-8.0 wt%.

6. The antioxidant jam according to claim 4, characterized in that, Intermediate B used in the antioxidant jam is further prepared into intermediate BP, which is prepared through the following steps: D1, the intermediate B obtained in steps B1-B4 is centrifuged, the relative centrifugal force of the centrifugation is 3000-8000g, the centrifugation time is 10-30min, and wet core-shell microcapsules are obtained. D2, the wet core-shell microcapsules are dried at an absolute pressure of 0.005-0.030 MPa and a temperature of 35-55℃ for 6-24 hours to obtain intermediate BP; wherein the water content of intermediate BP is 0.5-8.0 wt%.

7. The antioxidant jam according to claim 1, characterized in that, The fruit ingredients are selected from one or more of the following: strawberry, blueberry, raspberry, blackberry, mango, peach, apricot, apple, and pear; It also includes 0.05-0.30 parts by weight of trisodium citrate dihydrate, wherein when the trisodium citrate dihydrate is included by weight, the total weight of the fruit raw material and sucrose does not exceed 91.15 parts.

8. A method for preparing an antioxidant jam as described in any one of claims 1-7, characterized in that, Includes the following steps: S1 provides intermediate A or intermediate AP; S2 provides intermediate B or intermediate BP; S3: Mix fruit raw materials, sucrose and deionized water and heat to 60-95℃, maintain for 3-30 minutes and then concentrate under reduced pressure. S4, after cooling the material obtained in step S3 to 40-65°C, add intermediate A or intermediate AP, and intermediate B or intermediate BP, and mix for 5-30 minutes; Calcium salts may be added as needed to make the total amount of calcium ions added in the final antioxidant jam 0.02-0.25 parts in terms of calcium ions. The total amount of calcium ions added includes calcium ions introduced by intermediate A, calcium ions introduced by intermediate B, and calcium ions introduced by the added calcium salts. Under stirring, citric acid was added gradually to adjust the pH of the system to 2.8-3.6; S5, the material obtained in step S4 is filled, sealed, and subjected to heat treatment at a temperature of 85-95°C for 10-30 minutes to obtain the antioxidant jam.

9. The preparation method according to claim 8, characterized in that, The absolute pressure of the vacuum concentration in step S3 is 0.010-0.060 MPa, and the temperature of the vacuum concentration is 55-75℃. The endpoint of the vacuum concentration in step S3 is: the soluble solids content of the material is 20-70°Bx, which is measured by a refractometer at 20℃. After the vacuum concentration in step S3, the material is degassed under vacuum for 1-10 min.

10. The preparation method according to claim 8, characterized in that, In step S4, intermediate A or intermediate AP is added and mixed first, then intermediate B or intermediate BP is added and mixed. The mixing is performed by shear dispersion, and the rotation speed of the shear dispersion is 500-8000 rpm. The filling in step S5 is either hot filling or cold filling followed by heat treatment; The shear dispersion described in step S4 is performed using a high-speed shear emulsifier or a homogenizer; The antioxidant activity of the antioxidant jam was evaluated by measuring its DPPH free radical scavenging capacity.

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