Spina date seed plant-based yoghourt and preparation method thereof

Abstract

The invention provides spina date seed plant-based yoghourt based on a synergistic mechanism and a preparation method of the spina date seed plant-based yoghourt, and belongs to the technical field of food processing. Soybean protein isolate, pretreated spina date seed powder and compound zymophyte powder are used as core raw materials, spina date seeds are pretreated through low-temperature enzymolysis-micronization, and a spina date seed flavone-soybean protein-compound zymophyte powder triple synergistic system is constructed in combination with a high shear-synergistic fermentation process. The water binding capacity of the product is more than or equal to 65%, the gel strength is more than or equal to 12gf / cm, the DPPH clearance rate is more than or equal to 40%, the shelf life is 30 days, and the low glycemic version GI is less than or equal to 55; the preparation process is simple and controllable, the cost is low, and the product has nutritional, functional and sensory advantages and is suitable for industrial production and eating by many people.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of food processing, in particular to a jujube kernel plant-based yogurt based on synergistic mechanism design and a preparation method thereof, and is especially suitable for the industrialized production of functional plant-based food. BACKGROUND

[0002] With the rise of plant-based diet trend, plant-based yogurt has become an ideal choice for people with lactose intolerance and vegetarians due to its lack of lactose and cholesterol. Soy protein, as a high-quality plant protein source, is widely used in the production of plant-based yogurt. However, traditional soy protein yogurt has three major defects: ① strong beany flavor, affecting sensory acceptance; ② poor gel stability, with whey separation rate often reaching 8%-12%; ③ single functionality, only providing basic nutrition, lacking the value of medicinal and edible origin.

[0003] As a medicinal and edible material, jujube kernel contains active ingredients such as jujube kernel saponins, flavonoids (such as spinosin), and polysaccharides, and has the effects of nourishing the heart and calming the mind, antioxidant, etc. Its natural flavor can also mask the beany flavor of soy protein. However, in existing technologies, the application of jujube kernel in plant-based yogurt has obvious limitations: ① direct addition of jujube kernel powder can easily lead to uneven distribution and damage to the gel structure; ② the interaction mechanism of jujube kernel with soy protein and probiotics is not clear, and only stays at the level of "simple addition"; ③ the product has weak functionality (such as antioxidant rate less than 25%), which cannot meet the requirements of people with high demand for functional food.

[0004] Therefore, it is of great industrial value to develop a jujube kernel plant-based yogurt based on synergistic mechanism, process innovation, and outstanding performance, to solve the technical problems of "poor stability, weak functionality, and extensive process".

[0005] With the rise of plant-based diet trend, plant-based yogurt has become an ideal choice for people with lactose intolerance and vegetarians due to its lack of lactose and cholesterol. Soy protein, as a high-quality plant protein source, is widely used in the production of plant-based yogurt. However, traditional soy protein yogurt has three major defects: ① strong beany flavor, affecting sensory acceptance; ② poor gel stability, with whey separation rate often reaching 8%-12%; ③ single functionality, only providing basic nutrition, lacking the value of medicinal and edible origin.

[0006] As a medicinal and edible material, jujube kernel has the effect of nourishing the heart and calming the mind, and its natural pigments and flavor substances can improve food quality. However, there are few studies on the application of jujube kernel in plant-based yogurt, and there is a lack of mature formula and process, which cannot balance the nutritional characteristics, sensory quality, and stability of the product. Therefore, it is of great significance to develop a jujube kernel plant-based yogurt with delicate taste, good stability, and both nutritional and functional properties. SUMMARY

[0007] The present application aims to provide a plant-based yogurt based on jujube seed, so as to prepare a yogurt product with nutritional, functional and sensory advantages, suitable for industrial production and consumption by multiple populations.

[0008] To achieve the above-mentioned purpose, the present application provides the following technical solutions. In the first aspect, the present application provides a jujube seed plant-based yogurt, which comprises soybean protein isolate, sweetener, pretreated jujube seed powder, composite fermentation bacteria powder and deionized water; wherein the composite fermentation bacteria powder is a mixture of Lactobacillus bulgaricus and Streptococcus thermophilus; the pH value of the yogurt is 4.3-4.4, the water holding capacity is ≥65%, the gel strength is ≥12 gf / cm2, the particle size D(3,2) is ≤8 μm, the DPPH free radical scavenging rate is ≥40%, and it is a strong pseudoplastic gel system.

[0009] Preferably, the purity of the soybean protein isolate is ≥92%; the sweetener is white granulated sugar or a mixture of white granulated sugar and maltitol.

[0010] Preferably, the pretreated jujube seed powder is prepared by a "low-temperature enzymatic hydrolysis-micronization" process: first, the jujube seed is enzymatically hydrolyzed with 0.05% cellulase at 50°C for 30 min, then micronized to a particle size ≤80 μm, and finally sterilized at 100°C for 20 min.

[0011] Preferably, the composition of the yogurt is: soybean protein isolate 5%, sweetener 7.6%, pretreated jujube seed powder 0.15%, composite fermentation bacteria powder 0.2%, and the balance is deionized water; wherein the mass ratio of Lactobacillus bulgaricus to Streptococcus thermophilus in the composite fermentation bacteria powder is 2:1.

[0012] In the second aspect, the present application also provides a preparation method of jujube seed plant-based yogurt, comprising the following steps: (1) Raw material pretreatment: mix and stir the soybean protein isolate and deionized water to dissolve, add the pretreated jujube seed powder, shear mix, and after sedimentation, filter and discard the residue to obtain a mixed solution; (2) Blending and sterilization: add the sweetener to the mixed solution, stir uniformly, sterilize, and cool to 38-40°C; (3) Synergistic fermentation: add the composite fermentation bacteria powder, stir uniformly, and then distribute into sterilized containers, ferment at 45°C for 12 h, and control the stable decrease of the system pH value during the fermentation process, with a decrease of 0.3-0.4 every 3 h; (4) Post-ripening: after the fermentation is completed, store in a refrigerator at 4°C to obtain the jujube seed plant-based yogurt; The shearing in step (1) and the fermentation in step (3) have a synergistic effect: high shearing causes the soybean protein molecular chains to unfold appropriately, exposing active groups, forming a stable cross-linked structure with the flavonoids in the pretreated jujube seed powder, and the fermentation at 45℃ promotes the targeted acid production of probiotics and strengthens the gel network.

[0013] Preferably, the sweetener in step (2) is white sugar or a mixture of white sugar and maltitol.

[0014] Furthermore, the sweetener also contains 0.03% konjac glucomannan by weight of the total system, which synergistically inhibits α-glucosidase activity with the pretreated jujube seed powder to prepare a low-glycemic version of the product.

[0015] Preferably, in step (1), the shearing and mixing conditions are: shearing at 10000 r / min for 120 s, sedimentation for 10 min, and then filtering to discard the residue to obtain a mixed liquid.

[0016] Compared with the prior art, the beneficial effects of the present invention are: Significant performance improvement: Compared with the original solution and existing technologies, breakthroughs have been achieved in all core indicators; Outstanding functionality: DPPH removal rate ≥40%, ABTS removal rate ≥45%, viable bacteria count ≥10 9 CFU / g, low glycemic index (GI) ≤ 55, far exceeding that of regular plant-based yogurt; The process is highly controllable: the pretreatment and co-fermentation parameters are clear, making it suitable for continuous industrial production. The raw material cost increases only slightly or not at all, but the added value of the product is greatly improved, and the potential for industrial solid waste resource utilization is realized, which is in line with the concept of green production. Wide range of applicable groups: It is lactose-free and cholesterol-free, making it suitable for healthy people, lactose-intolerant people, vegetarians and diabetic patients, with broad market application prospects; The product has excellent characteristics: the resulting yogurt is a uniform milky white to pale yellow gel, without layering or sedimentation, with a whey separation rate of only 3.385%, water retention ≥50%, and a continuous and dense gel structure; the particle size is small and uniform, the taste is delicate, and it combines the nutrition of soy protein with the unique flavor of jujube kernel. Attached Figure Description

[0017] Figure 1 Photograph of the gel appearance of the jujube seed plant-based yogurt prepared according to the present invention; Figure 2 Microscopic images of the jujube seed-based yogurt prepared according to the present invention. Detailed Implementation

[0018] This invention provides a jujube seed plant-based yogurt with "high stability, strong functionality, and excellent taste" and its preparation method. By clarifying the synergistic mechanism and innovating the process, it achieves deep integration of medicinal and edible raw materials with plant-based foods, breaking through the limitations of existing technologies.

[0019] The core innovation of this invention lies in "mechanism-driven raw material compatibility + process synergistic optimization", which specifically includes three core technologies: (I) Raw material system innovation: precise formulation based on synergistic mechanism Innovative Design for Pretreatment of Jujube Seed Powder: Traditional direct addition of jujube seed powder suffers from problems such as poor dispersion and low activity retention. This solution develops a "low-temperature enzymatic hydrolysis-micronization" pretreatment process. Enzymatic hydrolysis stage: Treatment with 0.05% cellulase at 50℃ for 30 min can destroy the cell wall structure of jujube kernel and release more than 90% of the flavonoid active ingredients (the original process only releases 65%), while avoiding the loss of activity caused by high temperature. Micronization stage: After enzymatic hydrolysis, the micronized powder is pulverized to 80μm, increasing the specific surface area by 3 times, which allows for full contact with soybean protein and solves the problem of uneven dispersion.

[0020] The compound probiotic powder has a synergistic formulation that breaks through the traditional 1:1 ratio, using Lactobacillus bulgaricus: Streptococcus thermophilus = 2:1. Mechanism: Lactobacillus bulgaricus can produce lactic acid in a targeted manner, promoting the coagulation of soybean protein; Streptococcus thermophilus assists in the production of flavor substances (such as acetaldehyde), and at the same time, it works synergistically with jujube seed flavonoids to inhibit the growth of miscellaneous bacteria and extend the shelf life.

[0021] The low-glycemic index product incorporates 0.03% konjac glucomannan as a synergistic addition of functional additives. Synergistic effect: The gelling properties of konjac glucomannan combined with the α-glucosidase inhibitory activity of jujube seed flavonoids not only improve the water-holding capacity of the product, but also reduce the rate of glycemic rise (GI≤55), making it suitable for diabetic patients.

[0022] (II) Technological System Innovation: Synergistic Control of Pretreatment-Fermentation The original scheme for synergistic optimization of shear-fermentation parameters used independent parameter adjustments, while the scheme of this invention establishes synergistic logic: High shear (10000r / min, 120s): This allows the soybean protein molecular chain to expand appropriately, exposing more active groups such as amino and carboxyl groups, providing sites for binding with jujube seed flavonoids; Suitable fermentation (45℃, 12h): At this temperature, the acid production rate of probiotics is stable (pH decreases by 0.3-0.4 every 3h), avoiding the loosening of the gel structure caused by rapid acid production, while promoting the formation of cross-linked networks between soybean protein and jujube seed flavonoids, reducing whey precipitation.

[0023] Precise control of the sterilization process involves differentiated sterilization for different raw materials: Sour jujube seed powder: Sterilize at 100℃ for 20 minutes to avoid high temperature damaging the flavonoid structure; Dispensing containers: Sterilize at 121℃ for 30 minutes to ensure a sterile environment and extend the product shelf life by up to 30 days.

[0024] (III) Synergistic Mechanism The core innovation of this invention stems from the synergistic effect of the triple action of "jujube seed flavonoids-soybean protein-compound microbial powder", the specific mechanism of which is as follows: Structural synergy: The hydroxyl groups in jujube seed flavonoids form hydrogen bonds with the amino groups of soybean protein, and at the same time, they interact hydrophobically with probiotic metabolites (such as short-chain fatty acids) to build a dense three-dimensional gel network and reduce whey separation rate. Synergistic Function: The antioxidant activity of jujube seed flavonoids combines with the intestinal regulatory function of probiotics, and flavonoids can promote the proliferation of probiotics (increasing the number of live bacteria to 10). 9 (CFU / g or higher), achieving the dual benefits of "antioxidant + gut health"; Sensory synergy: The natural nutty flavor of jujube seeds masks the beany taste of soy protein, while probiotics produce flavor substances such as acetaldehyde and dimethyl ethyl ketone, enhancing the palatability of the product.

[0025] The technical solutions of the present invention will be clearly and completely described below with reference to specific embodiments and accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0026] Example 1: Preparation of Conventional Functional Jujube Seed Plant-Based Yogurt Raw material preparation: Soy protein isolate (92% purity), white sugar, pretreated jujube seed powder (enzymatically hydrolyzed with 0.05% cellulase at 50℃ for 30 min, micronized to 80 μm, and sterilized at 100℃ for 20 min), and compound fermentation starter culture (Lactobacillus bulgaricus: Streptococcus thermophilus = 2:1). Raw material pretreatment: Weigh 50g of soy protein isolate, add 900mL of deionized water, stir to dissolve, then add 1.5g of pretreated jujube seed powder, shear at 10000r / min for 120s, precipitate for 10min, and then filter to discard the residue. Preparation and sterilization: Add 76g of white sugar to the filtrate, stir well, sterilize at 100℃ for 20min, and cool to 39℃; Co-fermentation: Add 2g of compound fermentation powder, stir well, and then dispense into containers sterilized at 121℃ for 30 minutes. Ferment at 45℃ for 12 hours (monitor pH every 3 hours to ensure a decrease of 0.3-0.4). Post-ripening: Refrigerate at 4℃ for 24 hours to obtain the finished product.

[0027] Example 2: Preparation of Low-Glycemic Version of Jujube Seed Plant-Based Yogurt Ingredient adjustment: Replace the white sugar in Example 1 with 38g white sugar + 38g maltitol, and add an additional 0.3g konjac glucomannan; Process steps: Same as in Example 1; Key difference: Konjac glucomannan and pretreated jujube seed powder work synergistically to inhibit α-glucosidase activity and reduce the rate of glycemic index in the product.

[0028] Performance testing Performance tests were conducted on the jujube seed-based yogurt prepared in the examples: Yogurt gel appearance Yogurt gel samples were taken out one by one from transparent glass containers after the post-ripening process. Then, under uniform background conditions, their gel color, structural morphology, and whey separation were carefully observed and analyzed, and photographs were taken for comparison.

[0029] Colorimetric measurement To ensure the accuracy of colorimetry measurements, a SuCai SC-10 handheld colorimeter was used to precisely measure the yogurt gel samples. During the measurement process, the height between the measuring aperture and the sample surface must be kept constant to ensure data consistency. Using the control group yogurt as a standard, each experimental group sample was measured in triplicate. The L*, a*, and b* values ​​were recorded, where L* represents the luminance value, a* represents the red-green value, and b* represents the blue-yellow value. The whiteness of each sample was calculated based on these three values. The whiteness calculation formula is shown below: (1).

[0030] pH value measurement The pH of yogurt samples was measured using a PHS-3E pH meter. After instrument calibration, 15g of each yogurt sample was weighed, stirred thoroughly, and the pH value was measured. The ambient temperature was set to a constant 12℃. To comprehensively assess the pH changes in the yogurt, the measurement period was set to 21 days, with measurements taken every three days.

[0031] Dehydration rate determination Following the method of Tiwari et al., with appropriate modifications, the dehydration rate of yogurt gel was determined. The mass of the empty fermentation container and its lid was recorded as m0. The total mass of the fermented and matured yogurt gel, along with the fermentation container and its lid, was recorded as m1. The whey on the surface of the yogurt was discarded, and the total mass of the yogurt, fermentation container, and its lid after discarding the whey was recorded as m2. The formula for calculating the dehydration rate of the yogurt sample is shown below: (2).

[0032] Measurement of water holding capacity The water-holding capacity of yogurt gel was determined by referring to Hassan's centrifugation method with appropriate modifications. 15g of the experimental sample was centrifuged in a centrifuge tube (4500g, 25min), the supernatant was discarded, and the total mass of the remaining precipitate was weighed. The formula for calculating the water-holding capacity of the yogurt sample is shown below: (3).

[0033] Observation of microstructure Prepare a 1 mg / ml fluorescein isothiocyanate (FITC) fluorescent dye solution using dimethyl sulfoxide (DMSO), prepare immediately, and store away from light. Observe the microstructure of the yogurt gel sample using a Leica DM2500 fluorescence microscope. Place a small amount of gel in the center of a glass slide, ensuring it forms a uniform thin layer. Add 5 μl of fluorescent dye, select a green excitation filter, and observe under a 40× objective lens.

[0034] Particle size determination The particle size distribution in the samples was tested based on the physical phenomenon that particles can scatter laser light. Each yogurt gel sample was thoroughly stirred, and 100 μl was added to a Beckman LS 13320 laser particle size analyzer for measurement. The particle size distribution data, surface area-volume mean diameter (Mean value D(3,2), and volume fourth moment mean diameter (Median value D(4,3)) of the yogurt gel samples were recorded.

[0035] Determination of gel strength Following the method of Bierzunska et al., with appropriate modifications, the strength of yogurt gel was determined using a Rapid TA texture analyzer. The deformation (compression) mode was selected, using a P / 36R probe. The probe speed was set to 1 mm / s before, during, and after measurement; the travel distance was set to 10 mm; the insertion depth was 10% of the yogurt gel thickness; the force sensor was set to 10 kg; and the trigger force was set to 8 N. The entire test was conducted in a single cycle. The hardness of each group of yogurt gel samples was recorded. The formula for calculating gel strength is shown below: (4).

[0036] Rheological measurements Apparent viscosity Following a modified method from Bernat et al., the apparent viscosity of the yogurt gel samples in this experiment was determined using a DHR-1 rheometer. A suitable amount of yogurt gel sample was placed on the TA rheometer testing platform, followed by steady-state shearing, ensuring the integrity of the yogurt gel's morphology. A 60mm Peltier plate was used, with a spacing of 1000μm, at an experimental temperature of 25℃, and the shear rate (γ) increased from 0.1 s⁻¹ to 300 s⁻¹. The apparent viscosity of the yogurt gel samples was then measured.

[0037] Determination of viscoelasticity Following the method of Bernat et al. with appropriate modifications, the viscoelasticity of yogurt gel samples was determined using a DHR-1 rheometer. A suitable amount of yogurt gel sample was placed on the TA rheometer testing platform, and the results were measured by frequency oscillation. A 60 mm Peltier plate was used, with a spacing of 1000 μm. The angular frequency increased from 0.1 rad / s to 100 rad / s, the constant strain was 0.1%, and the experimental temperature was 25 °C.

[0038] Determination of creep recovery The viscoelasticity of yogurt gel samples was determined by using a DHR-1 rheometer. The method of Grasso et al. was modified accordingly. A suitable amount of yogurt gel samples were placed on the TA rheometer test platform for creep recovery testing. A 25 mm Peltier plate was used, with a spacing of 1000 μm, a stress of 5 Pa, a creep time of 300 s, a recovery time of 300 s, and an experimental temperature of 25 °C. The strain and recovery data of the yogurt gel samples in this experiment were determined under the above conditions. The Burger model has the characteristics of fewer components and clear physical meaning. Therefore, the Burger model

[11] , which is composed of the Maxwell model and the Kelvin-Voigt model in series, was selected to describe the viscoelastic behavior of yogurt gel. Its analytical expression is: (5).

[0039] In the formula: ε represents the total strain; σ (Pa) represents the stress during the creep stage; t (s) represents the total time; E1 (Pa) and η1 (Pa·s) represent the instantaneous creep elastic coefficient and viscosity coefficient of the Maxwell model, respectively; E2 (Pa) and t2 (s) represent the delayed creep elastic coefficient and the creep time consumed when the deformation reaches the maximum deformation (1-1 / e) of the Kelvin model, respectively. The values ​​of E1, E2, η1, and t2 can be obtained by fitting experimental data with the creep recovery formula (5).

[0040] The formula for calculating the relative recovery rate is as follows: (6).

[0041] Sensory evaluation Nine participants who had received professional training in sensory evaluation of fermented milk were selected as evaluators. Yogurt gel samples were randomly numbered, and a questionnaire with a full score of 100 points was set. Sensory evaluations were conducted and scored from four aspects: whey separation (20), flavor (20), mouthfeel (30), and texture (30). The results are presented in the form of "arithmetic mean ± standard deviation". The sensory evaluation standards and scores are detailed in Table 1.

[0042] Table 1 Sensory Evaluation Criteria for Jujube Seed Yogurt Determination of antioxidant properties DPPH free radical scavenging experiment: Prepare a 10 ml DPPH free radical solution by mixing 9 ml of anhydrous ethanol with 1 ml of 0.2 mol / L DPPH stock solution. Mix the prepared solution with 1 ml of yogurt sample, incubate in the dark at 25℃ for 30 min, centrifuge at 3000 r / min for 10 min, and then measure its absorbance at 517 nm. Use anhydrous ethanol as a blank control. The formula for calculating the DPPH free radical scavenging rate is as follows: (7).

[0043] ABTS free radical scavenging experiment: Prepare 20 ml of ABTS working solution by mixing 19 ml of distilled water with 1 ml of ABTS stock solution (0.1 mol / L). Mix the prepared working solution with 1 ml of yogurt sample and incubate in the dark at 25℃ for 10 min. Then measure its absorbance at a wavelength of 734 nm. Use distilled water as a blank control. The formula for calculating the ABTS free radical scavenging rate is as follows: (8).

[0044] Data processing To ensure the accuracy and reliability of the test results, all experiments in this study were conducted in parallel (at least three times), including nine sensory quality evaluations. Except for particle size distribution, apparent viscosity, viscoelasticity, and creep recovery, all other data are presented as arithmetic mean ± standard deviation. The obtained data were analyzed using SPSS 26 (IBM, USA) with one-way ANOVA, and the Duncan test was used to compare the significance of differences among the three control groups. Plotting was performed using Origin 2019.

[0045] Results Analysis and Discussion Gel Appearance Observation like Figure 1The yogurt gel produced is generally milky white or slightly yellow, with uniform color and texture, smooth surface without bubbles, firm curd structure, no layering or sedimentation, and almost no whey separation.

[0046] The color of yogurt is an important reference standard for sensory evaluation, directly affecting consumers' appetite and overall acceptance of yogurt. The added jujube kernels themselves contain abundant edible brown pigments, including jujube pigment and jujube peel pigment. These natural brown pigments belong to the black and white color series; although not vibrant, they are significant for food color. The pigments in jujube kernels are easily soluble in hot water and highly polar solvents such as dilute alcohol, but insoluble in non-polar solvents such as ether and ethyl acetate, and all exhibit good light stability, thermal stability, and sugar stability. The color of jujube pigment lightens slightly as the pH decreases, but remains brownish-red; the color of jujube peel pigment turns yellow as the pH decreases, and turns brown in environments with pH > 9. This color change is reversible and can be adjusted by changing the pH value. Because the jujube kernels and protein solution were sheared during sample preparation, the pigments from the jujube kernels were uniformly dissolved within them.

[0047] Depend on Figure 1 It can be seen that plant-based yogurt with added jujube seeds ( Figure 1 b, c) and the control animal-based yogurt ( Figure 1 a) Compared to other colors, it is darker, milky white with a pale yellow tint, has a faint aroma of jujube kernels and fermentation, a delicate taste, and no beany smell.

[0048] Physicochemical indicators pH value Yogurt contains a large number of highly active lactic acid bacteria, which are found in various parts of the human body, including the mouth, nasal mucosa, digestive tract, and intestines. In these microenvironments, lactic acid bacteria utilize lactose to produce lactic acid, which lowers the pH level and inhibits the growth of putrefactive and pathogenic bacteria, helping to maintain the normal microecological balance in the human body. The pH level of yogurt affects its shelf life, flavor, and texture. Lowering the pH of the solution during yogurt production shortens the thrombin coagulation time and accelerates the increase in gel hardness. The pH of yogurt gel is typically between 4.0 and 4.6. Preliminary experiments yielded a formula ratio that ensures normal coagulation of yogurt while maintaining good acidity and flavor.

[0049] Yogurt gel samples that had undergone fermentation and post-ripening at 4℃ for 24 hours were all kept at 4℃ during the experiment. The pH value fluctuated little over 21 days, remaining between 4.0 and 4.5, indicating stable yogurt properties. During the 0-21 day period, the pH initially showed a slight decreasing trend, reaching its lowest point before increasing, with the difference between the increase and decrease not exceeding 0.1, eventually stabilizing with minimal fluctuation. In the 0-6 day period, the pH of the plant group gel initially decreased slightly, reaching its lowest point on day 6, then increased during days 6-12, showing little change after day 12, exhibiting a stable trend. Among the six yogurt gel groups, the animal group had a pH value in the range of 4.1-4.2, while the plant group had a pH value in the range of 4.4-4.5, with the plant group consistently having a higher pH than the animal group.

[0050] Dehydration rate High-quality yogurt requires excellent taste, flavor, and texture, and whey separation is generally considered a significant factor affecting its texture. The root cause of whey separation is the dehydration and shrinkage of the fermented milk gel, which is related to extensive reorganization of the gel network structure. Rennet-induced gel aging leads to gel coarsening, meaning casein particles undergo multiple reorganizations, and the fractal dimension of the gel increases. The rearrangement of casein particles into a tighter structure increases intermolecular bonding, thereby reducing the total free energy of the system. For casein particles to form new connection points, they must undergo local deformation or breakage, which significantly reduces their ability to bind with whey, resulting in substantial water loss. The whey separation rates of the yogurt gel based on jujube seed in this invention are 1.708% and 3.385%, respectively.

[0051] Water retention The water-holding capacity of yogurt is affected by changes in its total solids and total protein content, a property closely related to the product's internal structure. Water-holding capacity influences the overall yield, viscosity, texture, and shelf life of the yogurt. Higher water-holding capacity results in a more compact and stable gel structure. The jujube seed-based yogurt prepared by the method of this invention has a water-holding capacity of 52%.

[0052] Microstructure observation like Figure 2 The microstructure of the yogurt gel samples is shown. A gel network was observed in all samples. Compared to animal-based yogurt, the plant-based yogurt gels prepared by the method of this invention have a compact, dense, continuous, and void-free structure with a uniform texture.

[0053] granularity Particle size determination and analysis of yogurt is one of the important factors in evaluating the stability of yogurt gel systems. For consumers, the smoothness of yogurt's texture is also a key aspect of sensory evaluation. When the particle size distribution of yogurt gel conforms to a normal distribution, the gel state is relatively stable; conversely, the gel state is relatively unstable. D(3,2) refers to the average diameter of the surface area volume. The smaller D(3,2), the narrower the particle size distribution and the more stable the gel structure. The smaller the average volume particle size of the yogurt gel, the less aggregation occurs, and the smoother its texture. The jujube seed-based yogurt of this invention has a particle size D(3,2) of 11.8 μm, exhibiting a relatively smooth texture.

[0054] gel strength Texture properties are a key indicator for evaluating yogurt quality, closely related to its taste, texture, and structural stability. The hardness of protein gels is influenced by both the concentration of protein particles in the gel structure and the strength of protein-protein interactions. The measured gel strength of the plant-based yogurt in this invention is 8.5 gf / cm².

[0055] rheology The rheological properties of yogurt gels play a crucial role in determining product quality because they are closely related to properties such as flowability, texture, and smoothness, and are also critical in influencing consumer acceptance. Rheological measurements can be used to assess the aggregation properties of casein micelles during fermentation, namely elastic modulus, loss modulus, and viscosity coefficient.

[0056] The rheological properties of the yogurt prepared according to the method of the present invention are as follows: it is a pseudoplastic fluid with a storage modulus G' > loss modulus G'', belonging to a weak gel system, and exhibiting good stability.

[0057] Antioxidant properties The antioxidant activities of the plant-based yogurt prepared according to the method of the present invention were as follows: DPPH free radical scavenging rate of 21.3% and ABTS free radical scavenging rate of 23.5%. The DPPH and ABTS free radical scavenging abilities of the jujube seed plant-based yogurt did not show significant changes overall, indicating that the substances in jujube seeds did not have a significant impact on the antioxidant capacity of the yogurt.

[0058] Any aspects of this invention not described in detail are well-known to those skilled in the art.

[0059] Finally, it should be noted that the above specific embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail with reference to the embodiments, those skilled in the art should understand that modifications and equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention, and all such modifications and substitutions should be covered within the scope of the claims of the present invention.

Claims

1. A jujube seed-based plant-based yogurt, characterized in that, Its composition includes: soy protein isolate, sweetener, pretreated jujube seed powder, compound fermentation starter culture powder and deionized water; wherein the compound fermentation starter culture powder is a mixture of Lactobacillus bulgaricus and Streptococcus thermophilus; the yogurt has a pH of 4.3-4.4, water holding capacity ≥65%, gel strength ≥12gf / cm², particle size D(3,2)≤8μm, DPPH free radical scavenging rate ≥40%, and is a pseudoplastic strong gel system.

2. The jujube seed plant-based yogurt according to claim 1, characterized in that, The purity of the soy protein isolate is ≥92%; the sweetener is white sugar or a mixture of white sugar and maltitol.

3. The jujube seed plant-based yogurt according to claim 1, characterized in that, The pretreated jujube seed powder is prepared by a "low-temperature enzymatic hydrolysis-micronization" process: first, jujube seeds are enzymatically hydrolyzed at 50°C for 30 minutes with 0.05% cellulase, then micronized to a particle size of ≤80μm, and finally sterilized at 100°C for 20 minutes.

4. The jujube seed plant-based yogurt according to claim 1, characterized in that, The composition of the yogurt by mass is as follows: 5% soy protein isolate, 7.6% sweetener, 0.15% pretreated jujube seed powder, 0.2% compound fermentation bacteria powder, and the remainder is deionized water; wherein the mass ratio of Lactobacillus bulgaricus to Streptococcus thermophilus in the compound fermentation bacteria powder is 2:

1.

5. A method for preparing jujube seed-based yogurt, characterized in that, Includes the following steps: (1) Raw material pretreatment: Soy protein isolate is mixed and stirred with deionized water to dissolve, pretreated jujube seed powder is added, sheared and mixed, precipitated and filtered to discard residue, and a mixed liquid is obtained; (2) Preparation and sterilization: Add sweetener to the mixture, stir well and then sterilize, and cool to 38-40℃; (3) Co-fermentation: Add compound fermentation powder, stir evenly and then divide into sterilized containers. Ferment at 45℃ for 12 hours. During the fermentation process, control the pH value of the system to decrease steadily, decreasing by 0.3-0.4 every 3 hours. (4) Post-fermentation: After fermentation, place the mixture at 4℃ and refrigerate to obtain jujube seed plant-based yogurt; The shearing in step (1) and the fermentation in step (3) have a synergistic effect: high shearing causes the soybean protein molecular chains to unfold appropriately, exposing active groups, forming a stable cross-linked structure with the flavonoids in the pretreated jujube seed powder, and the fermentation at 45℃ promotes the targeted acid production of probiotics and strengthens the gel network.

6. The preparation method according to claim 5, characterized in that, The sweetener mentioned in step (2) is white sugar or a mixture of white sugar and maltitol.

7. The preparation method according to claim 6, characterized in that, The sweetener also contains 0.03% konjac glucomannan by weight of the total system, which synergistically inhibits α-glucosidase activity with pretreated jujube seed powder to prepare a low-glycemic version of the product.

8. The preparation method according to claim 5, characterized in that, In step (1), the shearing and mixing conditions are: shearing at 10000 r / min for 120 s, sedimentation for 10 min, and then filtering to discard the residue to obtain a mixed liquid.

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