Low-temperature cold-pressing preparation method and application of mulberry composite fruit and vegetable juice

Abstract

The invention belongs to the technical field of food manufacturing, and particularly relates to a low-temperature cold-pressing preparation method and application of mulberry composite fruit and vegetable juice. The mulberry fruit and vegetable juice is prepared through raw material pretreatment, composite enzymolysis treatment, enzymolysis product obtaining, low-temperature cold pressing treatment, stability treatment, homogenization and degassing treatment and membrane filtration and sterilization treatment. The mulberry composite fruit and vegetable juice is applied to preparation of beverages and foods. By constructing a whole-course low-temperature, oxygen-isolating and multi-technology-synergistic processing system, multiple technical problems of nutrition retention, oxidation stability, juice yield, physical stability, flavor and the like in mulberry juice processing are effectively solved, and unification of high-activity component retention rate, long-term stability and natural wind feeling is realized.

Description

Technical Field

[0001] This invention belongs to the field of food manufacturing technology, specifically relating to a low-temperature cold-pressing preparation method of mulberry compound fruit and vegetable juice and its application. Background Technology

[0002] Mulberries, a fruit with extremely high nutritional value, have been loved by people since ancient times. They are rich in anthocyanins, resveratrol, vitamin C, amino acids, and various minerals, possessing multiple physiological functions such as antioxidant, anti-inflammatory, immune-boosting, and vision-protecting effects. In recent years, with increasing attention to healthy eating, the market demand for mulberries and their processed products has continued to grow.

[0003] Mulberries themselves have significant processing limitations. Their soft texture, high water content, and thin skin make them highly susceptible to spoilage after harvest due to mechanical damage and microbial infection, making storage and transportation extremely difficult. Therefore, processing mulberries into juice is a primary way to extend their shelf life and increase their added value. While plain mulberry juice retains some nutrients, its strong tartness limits consumer acceptance. More importantly, anthocyanins, the most valuable active ingredient in mulberries, are extremely sensitive to heat, light, and oxygen. Traditional juice processing techniques, such as blanching, high-temperature juicing, and pasteurization, while effectively killing microorganisms and increasing juice yield, inevitably lead to significant degradation of heat-sensitive nutrients like anthocyanins, resulting in dull color, reduced nutritional value, and deteriorated flavor.

[0004] To overcome these shortcomings, existing technologies have made various attempts. To increase juice yield, enzymatic hydrolysis or physical disruption methods are commonly used. Pectinase and cellulase are added to break down cell wall structures, but the effectiveness of enzymatic hydrolysis is heavily dependent on precise control of parameters such as temperature, pH, and time. Improper parameter combinations not only result in limited juice yield increases but may also produce off-flavors or lead to excessively high juice viscosity, affecting subsequent filtration. To address stability, various food colloids such as sodium carboxymethyl cellulose and xanthan gum are often added as stabilizers to prevent sedimentation and stratification. However, single stabilizers are often ineffective, and improper proportions of compound stabilizers can easily lead to a sticky texture or a noticeable chemical taste, affecting product quality. Regarding the preservation of nutrients, some technologies have attempted to use low-temperature pasteurization or autoclaving to replace traditional high-temperature sterilization, but these methods either pose safety risks due to incomplete sterilization, or involve high equipment investment making widespread adoption difficult, and their effectiveness in protecting color and flavor remains unsatisfactory.

[0005] Further analysis reveals that existing technological solutions are mostly localized optimizations targeting single problems, lacking a systematic and comprehensive approach. For example, enzymatic hydrolysis processes used to increase juice yield may damage flavor compounds due to harsh conditions; stabilizers added to maintain stability may react with polyphenols in the juice, affecting their bioactivity. The various process steps are disconnected and even inherently contradictory, making it difficult to achieve a balance in nutrition, taste, stability, and safety in the final product. Specifically, existing mulberry juice products generally suffer from prominent problems such as low retention of active ingredients, unstable color during storage, susceptibility to sedimentation, and an unharmonious and unnatural flavor.

[0006] Therefore, it is necessary to design a low-temperature cold-pressing preparation method for mulberry compound fruit and vegetable juice and its application. Summary of the Invention

[0007] To overcome the shortcomings of existing technologies, a low-temperature cold-pressing method for preparing mulberry compound fruit and vegetable juice is provided, along with its application.

[0008] To achieve the above objectives, the present invention provides the following technical solution: This invention provides a low-temperature cold-pressing method for preparing mulberry compound fruit and vegetable juice, comprising the following steps: 1) Raw material pretreatment: Fresh mulberries, apples, carrots and ginger are selected as raw materials and pretreated to obtain granular materials; 2) Compound enzymatic hydrolysis treatment: Add compound enzyme preparation to granular material, and carry out enzymatic hydrolysis reaction for 40-60 minutes at a temperature of 35-40℃ and a pH value controlled between 4.0 and 4.5 to obtain enzymatic hydrolysis product; 3) Low-temperature cold pressing treatment: The enzymatic hydrolysis product is transferred to a low-temperature cold pressing device and subjected to two-stage cold pressing at a temperature of 0-10℃. The juice produced by the two stages of pressing is collected and combined to obtain primary mulberry compound fruit and vegetable juice. 4) Stabilization treatment: Add compound stabilizer and emulsifier to the primary mulberry compound fruit and vegetable juice and stir to mix; 5) Homogenization and deaeration: The mixed juice obtained in step 4) is homogenized and deaerated; 6) Membrane filtration sterilization and filling: The deaerated juice obtained in step 5) is sterilized by membrane filtration and then filled to obtain the finished mulberry compound fruit and vegetable juice.

[0009] In step 1), the specific steps and parameters of the pretreatment are as follows: the raw materials are weighed and mixed according to the mass ratio of mulberry, apple, carrot and ginger of (60-80):(15-25):(8-12):(1-3), rinsed with clean water to remove surface impurities, drained and then crushed into granular materials of 3-5mm using a food-grade crusher.

[0010] The ginger raw material undergoes special pretreatment: fresh ginger is sliced ​​to a thickness of 2-3 mm, first dried with hot air at 45-50℃ for 30 min, then flash-frozen at -20℃ for 1 h, and finally restored to room temperature for later use.

[0011] In step 2), the compound enzyme preparation is composed of pectinase, cellulase, β-glucosidase, and lignin peroxidase mixed in a mass ratio of 1:(0.6-0.8):(0.2-0.4):(0.1-0.15), and the amount added is 0.3%-0.5% of the total mass of the granular material.

[0012] The compound enzyme preparation undergoes activation pretreatment before use: the compound enzyme preparation is dissolved in 0.1% CaCl2 solution and activated at 25-30℃ for 30 min, with the mass ratio of CaCl2 solution to compound enzyme preparation being (10~12):1.

[0013] During the enzymatic hydrolysis process, ultrasound with a frequency of 25-35 kHz is applied simultaneously for auxiliary treatment. The ultrasound is applied in a pulse mode with a working time of 2 seconds and an interval of 3 seconds, and the power density is controlled at 150-250 W / L. While applying ultrasound, ozone gas with a concentration of 0.1-0.3 mg / L is introduced into the enzymatic hydrolysis system at a flow rate of 0.5-1.0 L / min.

[0014] In step 3), the specific steps of the two-stage cold pressing process are as follows: under the protective environment of continuous introduction of food-grade nitrogen, the first stage of cold pressing is carried out at a pressure of 15-25 MPa for 8-12 minutes, and then the pressure is increased to 40-60 MPa for the second stage of cold pressing for 10-20 minutes.

[0015] In step 4) stabilization treatment, the composite stabilizer is composed of modified agar and gellan gum in a mass ratio of (2~3):1, and the amount added is 0.1%-0.2% of the mass of the primary mulberry compound fruit and vegetable juice; the emulsifier is composed of sodium alginate and citrus pectin in a mass ratio of (1~2):(2~3), and the amount added is 0.05%-0.1% of the mass of the primary mulberry compound fruit and vegetable juice. In step 4), tea polyphenols were added at a rate of 0.01%-0.03% of the total mass of the primary mulberry compound fruit and vegetable juice. The stirring and mixing were carried out at 10-15℃ and a speed of 30-50 rpm for 20-30 minutes.

[0016] The modification method of the modified agar is as follows: the agar is prepared into a 5% aqueous solution, the pH value is adjusted to 9.0-10.0 with NaOH, hydrolyzed at 60℃ for 30 min, and then the components with a molecular weight of 50,000-100,000 Daltons are collected using an ultrafiltration device and spray dried to obtain the modified agar.

[0017] In step 5), the homogenization and degassing process is as follows: first, the homogenizer is used to perform the first stage of homogenization at a pressure of 60-80 MPa, and then the homogenizer is used to perform the second stage of homogenization at a pressure of 20-30 MPa. Then, the homogenized juice is transferred to a vacuum degassing tank and degassed for 8-12 minutes at an absolute pressure of 0.06-0.08 MPa.

[0018] The mulberry compound fruit and vegetable juice prepared by the above method can be used in the preparation of beverages and food.

[0019] Compared with the prior art, the advantages and beneficial effects of the present invention are as follows: In the low-temperature cold-pressing preparation method of mulberry compound fruit and vegetable juice of the present invention: 1. This invention improves the retention rate of heat-sensitive active ingredients in mulberries by constructing a low-temperature and oxygen-free processing environment throughout the entire process. From the initial enzymatic hydrolysis treatment, the temperature is controlled within a relatively mild range. The subsequent low-temperature cold pressing treatment strictly limits the temperature to near the freezing point, supplemented by food-grade nitrogen protection. This measure effectively inhibits the loss of components such as anthocyanins due to thermal and oxidative degradation.

[0020] 2. This invention achieves a simultaneous improvement in juice yield and juice quality, thanks to the synergistic effect of compound enzymatic hydrolysis and ultrasound-assisted extraction. The compound enzyme preparation can decompose various structural substances in plant cell walls, while the physical force generated by the applied ultrasonic cavitation effect further disrupts cell structure, allowing for a more complete release of cell contents. This combination of biochemical and physical methods improves extraction efficiency, and because the processing conditions are mild, it avoids drastic damage to the inherent flavor substances and aromatic components in fruit cells, thus better preserving the natural flavor of the mulberry compound fruit and vegetable juice.

[0021] 3. This invention improves the stability of mulberry compound fruit and vegetable juice products through compound design in the stability treatment and subsequent homogenization and degassing processes. The modified agar, with its more concentrated molecular weight distribution, works synergistically with gellan gum and other components to form a denser and more stable three-dimensional network structure in the juice, effectively preventing the aggregation and sedimentation of solid particles. The subsequent secondary homogenization further refines the particles in the juice, enabling them to be stably suspended in the network. The subsequent vacuum degassing removes dissolved oxygen, preventing not only oxidative deterioration but also eliminating the potential damage to the stable system caused by air bubbles. These steps collectively ensure the uniformity and stability of the product throughout its shelf life.

[0022] 4. This invention also demonstrates advantages in flavor coordination and enhancement. The special pretreatment of ginger during the raw material pretreatment stage, using hot air drying to decompose gingerol into gingerone compounds through high temperature, combined with flash freezing, deactivates its pungent enzymes and triggers the rupture of cell ice crystals, thereby promoting the gentle release of flavor substances in subsequent processing, making its spiciness more mellow and well-complementing the fruity aroma of mulberry. The introduction of β-glucosidase in the compound enzymatic hydrolysis treatment, which hydrolyzes bound flavor precursors to release free aroma components, including geraniol acetate and geraniol butyrate, enhances the overall aroma richness and naturalness of the mulberry compound fruit and vegetable juice.

[0023] 5. The low-concentration ozone introduced simultaneously during the enzymatic hydrolysis process in this invention can be more evenly dispersed in an ultrasonic environment, playing a dual role in assisting sterilization and inhibiting enzymatic browning, thus providing a cleaner material basis for subsequent processes. Detailed Implementation

[0024] The technical solutions in the embodiments of the present invention will be clearly and completely described below. 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.

[0025] Unless otherwise specified, the chemical reagents and raw materials used in the following examples and comparative examples are all commercially available products.

[0026] In the specific embodiments of this application, the sources of various main raw materials are briefly described as follows: Pectinase, cellulase, β-glucosidase and lignin peroxidase: purchased from Ningxia Xiasheng Industrial Group Co., Ltd.; Sodium hydroxide: purchased from Langfang Qianyao Technology Co., Ltd. Calcium chloride: purchased from Shandong Shangshan Chemical Co., Ltd.; Agar, gellan gum, sodium alginate and citrus pectin: purchased from Shanghai Tongyi Biotechnology Co., Ltd.

[0027] Example 1 A method for preparing mulberry compound fruit and vegetable juice by low-temperature cold pressing 1) Raw material pretreatment: First, the ginger raw material undergoes special pretreatment by slicing it into 2 mm thick slices, drying it with hot air at 50℃ for 30 minutes, then flash-freezing it at -20℃ for 1 hour, and finally restoring it to room temperature for later use. Next, fresh mulberries, apples, carrots, and ginger are weighed in a mass ratio of 80:15:12:1, mixed, rinsed with water, and drained. The mixed raw materials are then crushed into granular materials with a particle size of 3 mm using a food-grade crusher.

[0028] 2) Compound Enzymatic Hydrolysis Treatment: A compound enzyme preparation, consisting of pectinase, cellulase, β-glucosidase, and lignin peroxidase in a mass ratio of 1:0.6:0.4:0.1, is added to the granular material at a rate of 0.3% of the total mass of the granular material. The enzyme preparation undergoes activation pretreatment before use, i.e., it is dissolved in a 0.1% CaCl2 solution and activated at 30℃ for 30 min. The mass ratio of CaCl2 solution to enzyme preparation is 10:1. The enzymatic hydrolysis reaction is carried out at 40℃ and pH 4.0 for 60 min. During the enzymatic hydrolysis process, 25 kHz ultrasound is simultaneously applied for auxiliary treatment using a pulse mode of 2 seconds on, 3 seconds off, with a power density controlled at 250 W / L. Simultaneously, ozone gas at a concentration of 0.1 mg / L is introduced into the enzymatic hydrolysis system at a rate of 1.0 L / min.

[0029] 3) Low-temperature cold pressing: After enzymatic hydrolysis, the hydrolysate is transferred to a low-temperature cold pressing device. Under the protection of food-grade nitrogen, the temperature is controlled at 0℃. The first stage of cold pressing is carried out at a pressure of 25MPa for 8 minutes. Then the pressure is increased to 40MPa for the second stage of cold pressing for 20 minutes. The juice is collected and combined to obtain primary mulberry compound fruit and vegetable juice.

[0030] 4) Stabilization Treatment: A composite stabilizer and emulsifier are added to the primary juice. The composite stabilizer is a mixture of modified agar and gellan gum in a 2:1 mass ratio, added at 0.1% of the primary juice mass. The emulsifier is a mixture of sodium alginate and citrus pectin in a 1:1 mass ratio, added at 0.1% of the primary juice mass. Simultaneously, 0.01% tea polyphenols are added to the primary juice mass. The modified agar is prepared as follows: agar is prepared into a 5% aqueous solution, the pH is adjusted to 9.0 with sodium hydroxide, hydrolyzed at 60℃ for 30 min, and then the components with a molecular weight of 50,000 to 100,000 Daltons are collected using an ultrafiltration device and spray-dried. The stabilization treatment mixing process is carried out at 15℃ and a stirring speed of 30 r / min for 30 min.

[0031] 5) Homogenization and degassing: First, the juice is homogenized at 80 MPa using a high-pressure homogenizer, then homogenized at 20 MPa. After that, the homogenized juice is degassed at 0.08 MPa for 8 minutes.

[0032] 6) Membrane filtration sterilization and filling: A membrane with a pore size of 0.22 μm is used for filtration sterilization at 4℃ and then filled in an aseptic environment to obtain the finished product.

[0033] Example 2 In this embodiment, the similarities to those in Embodiment 1 will not be repeated, and the differences are as follows: A method for preparing mulberry compound fruit and vegetable juice by low-temperature cold pressing 1) Raw material pretreatment: First, the ginger was pretreated to a thickness of 3mm, dried in hot air at 45℃ for 30min, and then flash-frozen at -20℃ for 1h. Mulberry, apple, carrot and ginger were weighed and mixed in a mass ratio of 60:25:8:3, and the treatment method was the same as in Example 1, and crushed into particles with a particle size of 5mm.

[0034] 2) Compound enzymatic hydrolysis treatment: The compound enzyme preparation was formulated with a mass ratio of pectinase, cellulase, β-glucosidase, and lignin peroxidase of 1:0.8:0.2:0.15, and the addition amount was 0.5%. Activation pretreatment was carried out at 25℃. The enzymatic hydrolysis reaction was carried out at 35℃ and pH 4.5 for 40 min. The ultrasonic frequency was 35 kHz, the power density was 150 W / L, the ozone concentration was 0.3 mg / L, and the injection rate was 0.5 L / min.

[0035] 3) In the low-temperature cold pressing process, the low-temperature cold pressing is carried out at 10°C under nitrogen protection. The first stage pressure is 15MPa for 12 minutes, and the second stage pressure is 60MPa for 10 minutes.

[0036] 4) In the stability treatment, the composite stabilizer was composed of modified agar and gellan gum in a 3:1 mass ratio, with an addition amount of 0.2%. The emulsifier was composed of sodium alginate and citrus pectin in a 2:3 mass ratio, with an addition amount of 0.05%. The tea polyphenols were added at 0.03%. The mixture was stirred and mixed at 10℃ and 50 r / min for 20 min.

[0037] 5) In the homogenization and degassing process, the homogenization pressure is 60 MPa for the first stage and 30 MPa for the second stage; the absolute pressure of degassing is 0.06 MPa and the time is 12 min.

[0038] 6) During homogenization and degassing, membrane filtration sterilization is carried out at 8°C, and finally, the finished mulberry compound fruit and vegetable juice is obtained by bottling.

[0039] Example 3 In this embodiment, the similarities to those in Embodiment 1 will not be repeated, and the differences are as follows: A method for preparing mulberry compound fruit and vegetable juice by low-temperature cold pressing 1) In the raw material pretreatment, the ginger is first pretreated to a thickness of 2.5 mm and dried in hot air at 47℃ for 30 min. Mulberry, apple, carrot and ginger are weighed and mixed in a mass ratio of 70:20:10:2 and crushed to a particle size of 4 mm.

[0040] 2) In the compound enzymatic hydrolysis treatment, the enzyme preparation ratio was 1:0.7:0.3:0.12, and the addition amount was 0.4%. Activation pretreatment was carried out at 27℃. The enzymatic hydrolysis reaction was carried out at 37℃ and pH 4.3 for 50 min. The ultrasonic frequency was 30kHz, the power density was 200W / L, the ozone concentration was 0.2 mg / L, and the injection rate was 0.7 L / min.

[0041] 3) In the low-temperature cold pressing process, the low-temperature cold pressing is carried out at 5°C. The first stage pressure is 20MPa for 10 minutes, and the second stage pressure is 50MPa for 15 minutes.

[0042] 4) In the stabilization treatment, the composite stabilizer was prepared by mixing modified agar and gellan gum in a 2:1 mass ratio, with an addition amount of 0.15%. The emulsifier was prepared by mixing sodium alginate and citrus pectin in a 1:2 mass ratio, with an addition amount of 0.075%. The tea polyphenols were added at 0.02%. The mixture was stirred and mixed at 12℃ and 40 r / min for 25 min.

[0043] 5) In the homogenization and degassing process, the homogenization pressure is 70 MPa for the first stage and 25 MPa for the second stage; the absolute pressure of degassing is 0.07 MPa and the time is 10 min.

[0044] 6) During homogenization and degassing, membrane filtration sterilization is carried out at 6℃, and finally, the finished mulberry compound fruit and vegetable juice is obtained by bottling.

[0045] Comparative Example 1 In this comparative example, the similarities with Example 1 will not be repeated, and the differences are as follows: The low-temperature cold pressing process was carried out in ambient air without the introduction of food-grade nitrogen for protection.

[0046] Comparative Example 2 In this comparative example, the similarities with Example 2 will not be repeated, and the differences are as follows: No β-glucosidase or lignin peroxidase was added in the compound enzymatic hydrolysis treatment; only pectinase and cellulase were used in a mass ratio of 1:1.

[0047] Comparative Example 3 In this comparative example, the similarities with Example 3 will not be repeated, and the differences are as follows: No modified agar was used in the stability treatment; instead, ordinary unmodified agar was used directly, and no homogenization treatment was performed.

[0048] Comparative Example 4 In this comparative example, the similarities with Example 1 will not be repeated, and the differences are as follows: The low-temperature cold pressing step was replaced with the traditional hot pressing process, with a hot pressing temperature of 70℃. The subsequent membrane filtration sterilization was eliminated, and high-temperature instantaneous sterilization at 95℃ for 30 seconds was adopted.

[0049] Comparative Example 5 In this comparative example, the similarities with Example 1 will not be repeated, and the differences are as follows: Ultrasonic assistance and ozone introduction were eliminated, and only conventional enzymatic hydrolysis was performed.

[0050] Performance Test Results and Analysis The quality indicators of the mulberry compound fruit and vegetable juice products prepared in the above three embodiments and five comparative examples were tested.

[0051] The testing methods are as follows: soluble solids content was determined using a handheld refractometer; pH value was determined using a pH meter; anthocyanin content was determined using the pH differential method and the retention rate was calculated, with the anthocyanin content of fresh mulberry raw material as 100% baseline; turbidity was determined using a turbidimeter, unit NTU; centrifugal sedimentation rate was calculated by centrifuging a certain amount of juice at 4000 r / min for 15 min and calculating the percentage of sediment volume to total volume; microbiological indicators were determined according to the national standard GB 4789.2, with total colony count; sensory evaluation was conducted by 10 trained evaluators, scoring on a 100-point scale based on color, aroma, taste, and texture. All samples were stored at 4℃ in the dark, and the above indicators were measured on day 0 and day 30, respectively. Stability-related indicators were based on the results measured on day 30. The specific test results are shown in Table 1.

[0052] Table 1 Analysis of Test Results

[0053] As shown in Table 1, the mulberry compound fruit and vegetable juices prepared in the three examples are significantly superior to the comparative example in all key indicators. The anthocyanin retention rates of Examples 1 to 3 all reached over 95%, far exceeding the 65.7% of Comparative Example 4. This fully demonstrates that the low-temperature and oxygen-free processing environment constructed in this invention, especially the low-temperature cold pressing at 0-10℃ combined with nitrogen protection, is crucial for protecting heat-sensitive anthocyanins. Comparative Example 1, due to the lack of nitrogen protection, saw its anthocyanin retention rate drop to 88.3%, indicating that oxidation is one of the important factors leading to the loss of active ingredients.

[0054] Regarding vitamin C retention, the vitamin C content of the examples was significantly higher than that of all comparative examples. The vitamin C content of Examples 1-3 was all above 17 mg / 100 mL, while the content of Comparative Example 4 (heat-processed) dropped sharply to 8.8 mg / 100 mL due to the high heat sensitivity of vitamin C, with a loss rate exceeding 65%. This further confirms the protective effect of low-temperature processing on water-soluble vitamins. Even Comparative Example 1, which did not use nitrogen protection, had a lower vitamin C content (14.1 mg / 100 mL) than the examples, indicating that oxidation is also a key factor in vitamin C loss.

[0055] Regarding oxidative stability, peroxide value is a key indicator for measuring the initial oxidative deterioration of a product. The peroxide values ​​of the examples were all below 0.35 meq / kg, indicating extremely low oxidation levels and pure flavor in the early stages of shelf life. In contrast, the peroxide values ​​of Comparative Example 1 (without nitrogen protection) and Comparative Example 4 (heat-processed) increased to 0.48 meq / kg and 1.05 meq / kg, respectively, indicating significant lipid oxidation. This not only destroys nutrients but also produces unpleasant flavors, affecting product quality. The peroxide value of Comparative Example 5 (without ultrasound and ozone) (0.58 meq / kg) was also higher than that of the examples, indicating that the strong oxidizing properties of ozone, under controlled dosages, can effectively kill microorganisms and deactivate endogenous oxidases, thus contributing to improved overall antioxidant stability.

[0056] Regarding juice stability and clarity, the turbidity of the examples was below 20 NTU, and the centrifugal sedimentation rate was below 1.5%, demonstrating excellent stability. In contrast, Comparative Example 3, due to the use of unmodified ordinary agar and the absence of homogenization, exhibited a turbidity as high as 45.2 NTU and a sedimentation rate of 8.9%. This indicates that modified agar with a specific molecular weight range obtained through alkaline hydrolysis and ultrafiltration, when combined with gellan gel and subjected to two-stage homogenization, can form a denser and more stable three-dimensional network structure, effectively suspending fine particles and preventing sedimentation.

[0057] In terms of juice extraction efficiency and flavor, the examples showed higher soluble solids content and better sensory scores than the comparative examples. Comparative Example 2 did not use β-glucosidase, which may have resulted in insufficient release of aroma components, leading to a lower sensory score. Comparative Example 5 omitted ultrasonic and ozone assistance, potentially affecting extraction efficiency and juice purity, resulting in a decrease in all indicators. Comparative Example 4 used traditional heat processing, which caused the most severe damage to nutritional components and flavor.

[0058] The technical solution of this invention systematically solves multiple technical problems in mulberry juice processing, such as nutrient retention, oxidative stability, juice yield, physical stability, and flavor, through the meticulous design and synergistic effect of each step.

[0059] This application effectively solves the common problems of easy loss of heat-sensitive nutrients, poor product stability and unpleasant flavor in mulberry juice processing by constructing a processing system that is low temperature, oxygen-free and multi-technology collaborative throughout the process, and achieves the unity of high active ingredient retention rate, long-term stability and natural flavor.

[0060] The above description represents the preferred embodiments of the present invention. It should be noted that those skilled in the art can make various improvements and modifications without departing from the principles of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method for preparing mulberry compound fruit and vegetable juice by low-temperature cold pressing, characterized in that, The method includes the following steps: 1) Raw material pretreatment: Fresh mulberries, apples, carrots and ginger are selected as raw materials and pretreated to obtain granular materials; 2) Compound enzymatic hydrolysis treatment: Add compound enzyme preparation to granular material, and carry out enzymatic hydrolysis reaction for 40-60 minutes at a temperature of 35-40℃ and a pH value controlled between 4.0 and 4.5 to obtain enzymatic hydrolysis product; 3) Low-temperature cold pressing treatment: The enzymatic hydrolysis product is transferred to a low-temperature cold pressing device and subjected to two-stage cold pressing at a temperature of 0-10℃. The juice produced by the two stages of pressing is collected and combined to obtain primary mulberry compound fruit and vegetable juice. 4) Stabilization treatment: Add compound stabilizer and emulsifier to the primary mulberry compound fruit and vegetable juice and stir to mix; 5) Homogenization and deaeration: The mixed juice obtained in step 4) is homogenized and deaerated; 6) Membrane filtration sterilization and filling: The deaerated juice obtained in step 5) is sterilized by membrane filtration and then filled to obtain the finished mulberry compound fruit and vegetable juice.

2. The method for preparing mulberry compound fruit and vegetable juice by low-temperature cold pressing according to claim 1, characterized in that, In step 1), the raw materials are weighed and mixed according to the mass ratio of mulberry, apple, carrot and ginger of (60-80):(15-25):(8-12):(1-3). The raw materials are rinsed with clean water to remove surface impurities, drained and then crushed into granular materials of 3-5mm using a food-grade crusher.

3. The method for preparing mulberry compound fruit and vegetable juice by low-temperature cold pressing according to claim 2, characterized in that, The ginger raw material mentioned in step 1) undergoes special pretreatment: fresh ginger is sliced ​​to a thickness of 2-3 mm, first dried with hot air at 45-50℃ for 30 minutes, then flash-frozen at -20℃ for 1 hour, and finally restored to room temperature for later use.

4. The method for preparing mulberry compound fruit and vegetable juice by low-temperature cold pressing according to claim 1, characterized in that, In step 2), the compound enzyme preparation is composed of pectinase, cellulase, β-glucosidase, and lignin peroxidase mixed in a mass ratio of 1:(0.6-0.8):(0.2-0.4):(0.1-0.15), and the amount added is 0.3%-0.5% of the total mass of the granular material.

5. The method for preparing mulberry compound fruit and vegetable juice by low-temperature cold pressing according to claim 4, characterized in that, Step 2) In the compound enzymatic hydrolysis treatment, the compound enzyme preparation is activated and pretreated before use: the compound enzyme preparation is dissolved in CaCl2 solution and activated at 25-30℃ for 30 min; During the enzymatic hydrolysis process in step 2), ultrasound with a frequency of 25-35 kHz is applied simultaneously for auxiliary treatment. The ultrasound is applied in a pulse mode with a working time of 2 seconds and an interval of 3 seconds, and the power density is controlled at 150-250 W / L. While applying ultrasound, ozone gas with a concentration of 0.1-0.3 mg / L is introduced into the enzymatic hydrolysis system at a flow rate of 0.5-1.0 L / min.

6. The method for preparing mulberry compound fruit and vegetable juice by low-temperature cold pressing according to claim 1, characterized in that, Step 3) In the low-temperature cold pressing process, the specific steps of the two-stage cold pressing are as follows: Under the protective environment of continuous introduction of food-grade nitrogen, the first stage of cold pressing is carried out at a pressure of 15-25 MPa for 8-12 minutes, and then the pressure is increased to 40-60 MPa for the second stage of cold pressing for 10-20 minutes.

7. The method for preparing mulberry compound fruit and vegetable juice by low-temperature cold pressing according to claim 1, characterized in that, In step 4) the stability treatment, the composite stabilizer is composed of modified agar and gellan gum in a mass ratio of (2~3):1, and the amount added is 0.1%-0.2% of the mass of the primary mulberry compound fruit and vegetable juice; The emulsifier is a compound of sodium alginate and citrus pectin in a mass ratio of (1~2):(2~3), and the amount added is 0.05%-0.1% of the mass of the primary mulberry compound fruit and vegetable juice; In step 4) the stabilization treatment, tea polyphenols were also added at a rate of 0.01%-0.03% of the total mass of the primary mulberry compound fruit and vegetable juice. The stirring and mixing is carried out at 10-15℃ and a speed of 30-50 rpm for 20-30 minutes.

8. The method for preparing mulberry compound fruit and vegetable juice by low-temperature cold pressing according to claim 7, characterized in that, The modification method of the modified agar is as follows: the agar is prepared into a 5% aqueous solution, the pH value is adjusted to 9.0-10.0 with NaOH, hydrolyzed at 60℃ for 30 min, and then the components with a molecular weight of 50,000-100,000 Daltons are collected using an ultrafiltration device and spray dried to obtain the modified agar.

9. The method for preparing mulberry compound fruit and vegetable juice by low-temperature cold pressing according to claim 1, characterized in that, In step 5), the homogenization and degassing process is as follows: first, the homogenizer is used to perform the first stage of homogenization at a pressure of 60-80 MPa, and then the second stage of homogenization is performed at a pressure of 20-30 MPa. Then, the homogenized juice is transferred to a vacuum degassing tank and degassed for 8-12 minutes at an absolute pressure of 0.06-0.08 MPa.

10. The application of a mulberry compound fruit and vegetable juice obtained by the low-temperature cold-pressing preparation method according to any one of claims 1-9, characterized in that, The mulberry compound fruit and vegetable juice is used in the preparation of beverages and food.

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