Preparation method of mixed berry yoghourt

Abstract

The invention discloses a preparation method of mixed berry yoghurt, which comprises the following steps: (1) preparing soy isolate protein powder enzymatic hydrolysate, and dividing the enzymatic hydrolysate into two parts, namely enzymatic hydrolysate I and enzymatic hydrolysate II; (2) preparing a mushroom extracting solution; adding the enzymatic hydrolysate I to obtain a composite liquid I; (3) adding pepsin into the enzymatic hydrolysate II, and adding threonine and L-lysine to obtain a compound liquid II; (4) mixing the strawberry particles, the blueberry particles and the raspberry particles to obtain mixed particles, and crushing and stirring the mixed particles to obtain mixed raspberry pulp; and mixing raw milk, white granulated sugar, the compound liquid I, the compound liquid II and the mixed berry pulp, performing homogenization treatment, performing pasteurization, inoculating a fermentation strain, performing fermentation, and performing cold storage so as to obtain the mixed berry yoghourt. The yoghurt prepared by the method disclosed by the invention has relatively high water holding capacity, good tissue form and fine and uniform texture; the fruit fragrance is strong, and the taste is very good.

Description

Technical Field

[0001] The present invention relates to the technical field of yogurt manufacturing, and particularly relates to a preparation method of mixed berry yogurt. Background Art

[0002] Yogurt is a product fermented from raw cow (sheep) milk or milk powder through sterilization and inoculation with Streptococcus thermophilus and Lactobacillus bulgaricus, and has various health care functions such as adjusting the balance of intestinal flora, alleviating lactose intolerance, reducing cholesterol, antioxidant and anti-aging, and lowering blood pressure. With the increasing attention and awareness of consumers towards healthy and safe diets, the requirements for the nutritional value and physiological effects of yogurt are gradually increasing. At the same time, new products formed by adding nutrient-rich fruits and vegetables into yogurt have also started to enter the field of vision of consumers. The evaluation of antioxidant properties, promotion of gastrointestinal health, digestion and absorption, improvement of physiological functions and certain health care effects of fruit and vegetable yogurt have become research hotspots in nutrition. Summary of the Invention

[0003] Therefore, the present invention provides a preparation method of mixed berry yogurt, and the preparation steps include:

[0004] (1) Prepare an aqueous solution of neutral protease, add soy protein isolate powder to the aqueous solution of neutral protease, stir and mix for more than 20 min, then heat to 45 ± 3 °C, keep the temperature constant for enzymatic hydrolysis for 3 - 5 h, perform enzyme inactivation treatment after enzymatic hydrolysis is completed, perform solid-liquid separation, and concentrate the liquid phase under reduced pressure to obtain an enzymatic hydrolysate. Divide the enzymatic hydrolysate into two parts: enzymatic hydrolysate I and enzymatic hydrolysate II;

[0005] (2) Chop dried shiitake mushrooms and then grind them into powder to obtain shiitake mushroom powder. Immerse the shiitake mushroom powder in deionized water, then heat to 90 ± 5 °C and keep the temperature constant for extraction for 90 - 150 min. After extraction is completed, perform solid-liquid separation to obtain an extract. Heat the extract in a water bath to 60 ± 3 °C and keep the temperature constant, then add the enzymatic hydrolysate I to the extract under stirring. After adding the materials, continue to keep the temperature constant at 60 ± 3 °C and stir for more than 40 min. After the heat preservation is ended, cool to room temperature in air to obtain composite liquid I;

[0006] (3) Add pepsin to the enzymatic hydrolysate II. After adding the materials, stir for more than 20 min to mix evenly, then add threonine and L-lysine under stirring. After adding the materials, adjust the pH to 5 - 5.5, then stir for more than 20 min, and then heat in a water bath to 37 ± 2 °C, keep the temperature constant and stir for more than 5 h. After stirring is completed, perform enzyme inactivation treatment to obtain composite liquid II;

[0007] (4) Mix strawberry granules, blueberry granules and raspberry granules to obtain mixed granules. Crush and stir the mixed granules evenly in a blender to obtain a fruit pulp solution. Filter the fruit pulp solution with gauze, and after filtration, perform pasteurization to obtain a mixed berry juice. Mix raw milk, granulated sugar, the compound solution I, compound solution II, and the mixed berry juice, perform homogenization treatment, inoculate fermentation strains after pasteurization, ferment at 42 ± 2 °C for 6 - 7 h, and then refrigerate at 0 - 4 °C for 10 - 12 h to obtain the mixed berry yogurt.

[0008] Further, in the step (1), in the aqueous solution of neutral protease, the mass percentage of neutral protease is 4% - 6%, and the mass ratio of soy protein isolate added to the aqueous solution of neutral protease is soy protein isolate: aqueous solution of neutral protease = 5 - 8:100.

[0009] Further, in the step (1), the enzyme hydrolyzate is divided into two equal - volume parts, namely enzyme hydrolyzate I and enzyme hydrolyzate II.

[0010] Further, in the step (2), the mass ratio of the shiitake mushroom powder soaked in deionized water is shiitake mushroom powder: deionized water = 1:50 - 100.

[0011] Further, in the step (2), the volume ratio of adding the enzyme hydrolyzate I to the extract is extract: enzyme hydrolyzate I = 3 - 5:1.

[0012] Further, in the step (3), add pepsin to the enzyme hydrolyzate II so that the mass percentage of pepsin is 1.4% - 1.6%, and add threonine and L - lysine so that the mass percentage of threonine is 1% - 1.5%, and the mass percentage of L - lysine is 1% - 1.5%.

[0013] Further, in the step (4), the mass ratio of mixing strawberry granules, blueberry granules and raspberry granules is strawberry granules: blueberry granules: raspberry granules = 10:1 - 10:1 - 10.

[0014] Further, in the step (4), the mixing ratio of raw milk, granulated sugar, the compound solution I, compound solution II, and the mixed berry juice is raw milk: granulated sugar: compound solution I: compound solution II: mixed berry juice = 100 mL: 6 - 8 g: 4 - 8 mL: 5 - 10 mL: 15 - 18 mL.

[0015] The beneficial effects of the present invention are as follows: The yogurt prepared by the method of the present invention has a high water holding rate, good tissue morphology, and delicate and uniform texture; it has a strong fruity aroma and a very good taste. In the present invention, soy polypeptide is obtained by enzymatically hydrolyzing soy protein isolate powder, and then hydrogen bond crosslinking is formed by combining soy polypeptide and lentinan to form a network structure that can enhance the water holding capacity of yogurt. Furthermore, hydrophilic amino acids such as threonine and L-lysine are introduced for modification, and intermolecular forces such as hydrogen bonds and van der Waals forces formed by hydrophilic amino acid groups and water molecules are utilized to further improve the water holding capacity of yogurt. In addition, by adding a mixture of strawberries, blueberries and raspberries, the taste and nutrition of yogurt are improved. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 It is a comparison chart of the water holding rates of the yogurts prepared by the methods of each example and comparative example. DETAILED DESCRIPTION OF THE INVENTION

[0017] The present invention will be further described below in conjunction with examples.

[0018] Example 1

[0019] A preparation method of a mixed-berry yogurt, the preparation steps include:

[0020] (1) Prepare an aqueous solution of neutral protease (20000 U / g), in the aqueous solution of neutral protease, the mass percentage of neutral protease is 6%, add soy protein isolate powder to the aqueous solution of neutral protease, and the mass ratio of soy protein isolate powder to the aqueous solution of neutral protease is soy protein isolate powder: aqueous solution of neutral protease = 5:100; stir and mix for 20 min, then heat to 45 °C and keep the temperature constant for enzymatic hydrolysis for 3 h. After the enzymatic hydrolysis is completed, inactivate the enzyme, separate the solid and liquid, and concentrate the liquid phase under reduced pressure to 1 / 2 of the volume before concentration to obtain an enzymatic hydrolysate. Divide the enzymatic hydrolysate into two equal-volume parts, namely enzymatic hydrolysate I and enzymatic hydrolysate II;

[0021] (2) Chop dried mushrooms and grind them into powder to obtain mushroom powder. Soak the mushroom powder in deionized water, and the mass ratio of mushroom powder to deionized water is mushroom powder: deionized water = 1:50; then heat to 90 °C and keep the temperature constant for extraction for 90 min. After the extraction is completed, separate the solid and liquid to obtain an extract; heat the extract in a water bath to 60 °C and keep the temperature constant, and then add the enzymatic hydrolysate I to the extract under stirring. The volume ratio of the extract to the enzymatic hydrolysate I added to the extract is extract: enzymatic hydrolysate I = 3:1; after the feeding is completed, continue to stir at 60 °C for 40 min. After the heat preservation is completed, cool to room temperature in air to obtain composite liquid I;

[0022] (3) Add pepsin (4200 U / g) to the enzymatic hydrolysate II. Add pepsin to the enzymatic hydrolysate II such that the mass percentage of pepsin is 1.4%. After the addition is complete, stir for 20 min to mix evenly. Then, add threonine and L-lysine while stirring. The added mass of threonine and L-lysine is such that the mass percentage of threonine is 1% and the mass percentage of L-lysine is 1.5%. After the addition is complete, adjust the pH to 5 with citric acid, then stir for 20 min, and then heat in a water bath to 37 °C and keep stirring for 5 h. After stirring is complete, perform enzyme inactivation treatment to obtain the composite solution II.

[0023] (4) Mix strawberry granules, blueberry granules, and raspberry granules to obtain mixed granules. The mixing mass ratio of strawberry granules: blueberry granules: raspberry granules is 10:1:1. The mixed granules are pulverized and stirred evenly in a stirrer to obtain a fruit pulp solution, which is filtered through a gauze, and after filtration, pasteurized to obtain a mixed berry pulp solution. Mix raw milk, granulated sugar, the composite solution I, the composite solution II, and the mixed berry pulp solution. The mixing ratio of raw milk: granulated sugar: composite solution I: composite solution II: mixed berry pulp solution is 100 mL: 6 g: 4 mL: 10 mL: 15 mL. Perform homogenization treatment, and after pasteurization, inoculate with a fermentation strain (a mixed fermentation strain of Lactobacillus delbrueckii subsp. bulgaricus and Streptococcus thermophilus in a 1:1 ratio, inoculation amount 0.2% w / v), ferment at 42 °C for 6 h, and then refrigerate at 4 °C for 10 h to obtain the mixed berry yogurt.

[0024] Example 2

[0025] A method for preparing a mixed berry yogurt, the preparation steps include:

[0026] (1) Prepare an aqueous solution of neutral protease (20000 U / g). In the aqueous solution of neutral protease, the mass percentage of neutral protease is 5%. Add soy protein isolate to the aqueous solution of neutral protease. The mass ratio of soy protein isolate to the aqueous solution of neutral protease is 6:100. Stir and mix for 20 min, then heat to 45 °C and perform constant-temperature enzymatic hydrolysis for 4 h. After enzymatic hydrolysis is complete, perform enzyme inactivation treatment, perform solid-liquid separation, and concentrate the liquid phase under reduced pressure to 1 / 2 of the volume before concentration to obtain an enzymatic hydrolysate. Divide the enzymatic hydrolysate into two equal volumes, namely enzymatic hydrolysate I and enzymatic hydrolysate II.

[0027] (2) Chop the dried shiitake mushrooms and grind them into powder to obtain shiitake mushroom powder. The shiitake mushroom powder is soaked in deionized water, and the mass ratio of the shiitake mushroom powder soaked in deionized water is shiitake mushroom powder:deionized water = 1:50. Then heat it to 90°C and keep it warm for extraction for 90 minutes. After the extraction is completed, perform solid-liquid separation to obtain the extract. Heat the extract in a water bath to 60°C and keep it warm. Then, under stirring, add the enzymatic hydrolysate I to the extract. The volume ratio of the extract to the enzymatic hydrolysate I added to the extract is extract:enzymatic hydrolysate I = 4:1. After the addition of the materials is completed, continue to stir and keep it warm at 60°C for 40 minutes. After the insulation is completed, air-cool it to room temperature to obtain the composite liquid I;

[0028] (3) Add pepsin (4200 U / g) to the enzymatic hydrolysate II, and add pepsin to the enzymatic hydrolysate II so that the mass percentage of pepsin is 1.5%. After the addition of the materials is completed, stir for 20 minutes to mix evenly. Then, under stirring, add threonine and L-lysine. The added masses of threonine and L-lysine are such that the mass percentage of threonine is 1% and the mass percentage of L-lysine is 1.5%. After the addition of the materials is completed, adjust the pH to 5 with citric acid, then stir for 20 minutes, and then heat it in a water bath to 37°C, keep it warm and stir for 5 hours. After the stirring is completed, perform enzyme inactivation treatment to obtain the composite liquid II;

[0029] (4) Mix strawberry granules, blueberry granules and raspberry granules to obtain mixed granules. The mixing mass ratio of the strawberry granules, blueberry granules and raspberry granules is strawberry granules:blueberry granules:raspberry granules = 10:5:5. The mixed granules are pulverized and stirred evenly in a stirrer to obtain a fruit pulp solution, and the fruit pulp solution is filtered with gauze, and after filtration, it is pasteurized to obtain a mixed berry pulp liquid. Mix raw cow milk, granulated sugar, the composite liquid I, the composite liquid II and the mixed berry pulp liquid. The mixing ratio of raw cow milk, granulated sugar, the composite liquid I, the composite liquid II and the mixed berry pulp liquid is raw cow milk:granulated sugar:composite liquid I:composite liquid II:mixed berry pulp liquid = 100 mL:7 g:6 mL:7 mL:16 mL. Perform homogenization treatment, and after pasteurization, inoculate with fermentation strains (a mixed fermentation strain of Lactobacillus delbrueckii subsp. bulgaricus and Streptococcus thermophilus in a ratio of 1:1, inoculation amount 0.2% w / v), ferment at 42°C for 6 hours, and then refrigerate at 4°C for 10 hours to obtain the mixed berry yogurt.

[0030] Example 3

[0031] A method for preparing a mixed berry yogurt, the preparation steps include:

[0032] (1) Prepare an aqueous solution of neutral protease (20000 U / g). In the aqueous solution of neutral protease, the mass percentage of neutral protease is 5%. Add soy protein isolate powder to the aqueous solution of neutral protease. The mass ratio of soy protein isolate powder to the aqueous solution of neutral protease is soy protein isolate powder : aqueous solution of neutral protease = 7:100. Stir and mix for 20 min, then heat to 45 °C and carry out constant-temperature enzymatic hydrolysis for 4 h. After the enzymatic hydrolysis is completed, inactivate the enzyme, carry out solid-liquid separation, and concentrate the liquid phase under reduced pressure to 1 / 2 of the volume before concentration to obtain an enzymatic hydrolysate. Divide the enzymatic hydrolysate into two equal-volume parts, enzymatic hydrolysate I and enzymatic hydrolysate II;

[0033] (2) Chop dried shiitake mushrooms and then grind them into powder to obtain shiitake mushroom powder. Soak the shiitake mushroom powder in deionized water. The mass ratio of shiitake mushroom powder to deionized water is shiitake mushroom powder : deionized water = 1:50. Then heat to 90 °C and keep warm for extraction for 90 min. After the extraction is completed, carry out solid-liquid separation to obtain an extract. Heat the extract in a water bath to 60 °C and keep warm. Then, under stirring conditions, add enzymatic hydrolysate I to the extract. The volume ratio of the extract to enzymatic hydrolysate I added to the extract is extract : enzymatic hydrolysate I = 4:1. After the addition of materials is completed, continue to keep warm and stir at 60 °C for 40 min. After the heat preservation is ended, air-cool to room temperature to obtain composite liquid I;

[0034] (3) Add pepsin (4200 U / g) to enzymatic hydrolysate II. Add pepsin to enzymatic hydrolysate II so that the mass percentage of pepsin is 1.5%. After the addition of materials is completed, stir for 20 min to mix evenly. Then, under stirring conditions, add threonine and L-lysine. The added masses of threonine and L-lysine are such that the mass percentage of threonine is 1.5% and the mass percentage of L-lysine is 1%. After the addition of materials is completed, adjust the pH to 5 with citric acid, then stir for 20 min, and then heat in a water bath to 37 °C and keep warm and stir for 5 h. After the stirring is completed, inactivate the enzyme to obtain composite liquid II;

[0035] (4) Mix strawberry particles, blueberry particles and raspberry particles to obtain mixed particles. The mixing mass ratio of the strawberry particles, blueberry particles and raspberry particles is strawberry particles: blueberry particles: raspberry particles = 10:5:5. The mixed particles are crushed and stirred evenly in a blender to obtain a pulp solution, and the pulp solution is filtered with gauze, and after filtration, pasteurized to obtain a mixed berry slurry. Mix raw milk, granulated sugar, the composite liquid I, composite liquid II and the mixed berry slurry. The mixing ratio of raw milk, granulated sugar, the composite liquid I, composite liquid II and the mixed berry slurry is raw milk: granulated sugar: composite liquid I: composite liquid II: mixed berry slurry = 100 mL: 7 g: 6 mL: 9 mL: 17 mL. After homogenization treatment and pasteurization, add fermentation strains (a 1:1 mixed fermentation strain of Lactobacillus delbrueckii subsp. bulgaricus and Streptococcus thermophilus, inoculation amount 0.2% w / v), ferment at 42 °C for 6 h, and then refrigerate at 4 °C for 10 h to obtain the mixed berry yogurt.

[0036] Example 4

[0037] A preparation method of a mixed berry yogurt, and the preparation steps include:

[0038] (1) Prepare an aqueous solution of neutral protease (20000 U / g). In the aqueous solution of neutral protease, the mass percentage of neutral protease is 6%. Add soy protein isolate to the aqueous solution of neutral protease. The mass ratio of soy protein isolate to the aqueous solution of neutral protease is soy protein isolate: aqueous solution of neutral protease = 8:100. Stir and mix for 20 min, then heat to 45 °C and keep the temperature for enzymatic hydrolysis for 3 h. After the enzymatic hydrolysis is completed, inactivate the enzyme, separate the solid and liquid, and concentrate the liquid phase under reduced pressure to 1 / 2 of the volume before concentration to obtain an enzymatic hydrolysate. Divide the enzymatic hydrolysate into two equal parts, enzymatic hydrolysate I and enzymatic hydrolysate II;

[0039] (2) Cut dried mushrooms into pieces and grind them into powder to obtain mushroom powder. The mushroom powder is soaked in deionized water. The mass ratio of the mushroom powder soaked in deionized water is mushroom powder: deionized water = 1:50. Then heat to 90 °C and keep the temperature for extraction for 90 min. After the extraction is completed, separate the solid and liquid to obtain an extract. Heat the extract in a water bath to 60 °C and keep the temperature, and then add the enzymatic hydrolysate I to the extract under stirring. The volume ratio of the extract to the enzymatic hydrolysate I added to the extract is extract: enzymatic hydrolysate I = 5:1. After the addition of the material is completed, continue to stir at 60 °C for 40 min. After the heat preservation is completed, air-cool to room temperature to obtain the composite liquid I;

[0040] (3) Add pepsin (4200 U / g) to the enzymatic hydrolysate II, and add pepsin to the enzymatic hydrolysate II such that the mass percentage of pepsin is 1.6%. After the feeding is completed, stir for 20 min to mix evenly. Then, add threonine and L-lysine under stirring. The added mass of threonine and L-lysine is such that the mass percentage of threonine is 1.5% and the mass percentage of L-lysine is 1%. After the feeding is completed, adjust the pH to 5 with citric acid, then stir for 20 min, and then heat in a water bath to 37 °C and keep stirring for 5 h. After the stirring is completed, perform enzyme inactivation treatment to obtain the composite solution II;

[0041] (4) Mix strawberry granules, blueberry granules, and raspberry granules to obtain mixed granules. The mixing mass ratio of the strawberry granules, blueberry granules, and raspberry granules is strawberry granules: blueberry granules: raspberry granules = 10:10:10. The mixed granules are pulverized and stirred evenly in a stirrer to obtain a fruit pulp solution, and the fruit pulp solution is filtered with a gauze, and after filtration, pasteurized to obtain a mixed berry pulp solution. Mix raw milk, granulated sugar, the composite solution I, the composite solution II, and the mixed berry pulp solution. The mixing ratio of raw milk, granulated sugar, the composite solution I, the composite solution II, and the mixed berry pulp solution is raw milk: granulated sugar: composite solution I: composite solution II: mixed berry pulp solution = 100 mL: 8 g: 8 mL: 5 mL: 18 mL. Perform homogenization treatment, and after pasteurization, inoculate with a fermentation strain (a mixed fermentation strain of Lactobacillus delbrueckii subsp. bulgaricus and Streptococcus thermophilus in a ratio of 1:1, inoculation amount 0.2% w / v), ferment at 42 °C for 6 h, and then refrigerate at 4 °C for 10 h to obtain the mixed berry yogurt.

[0042] Comparative Example 1

[0043] A preparation method of a mixed berry yogurt for comparison, and the preparation steps include:

[0044] (1) Prepare an aqueous solution of neutral protease (20000 U / g). In the aqueous solution of neutral protease, the mass percentage of neutral protease is 5%. Add soy protein isolate to the aqueous solution of neutral protease. The mass ratio of soy protein isolate to the aqueous solution of neutral protease is soy protein isolate: aqueous solution of neutral protease = 7:100. Stir and mix for 20 min, then heat to 45 °C and keep the temperature for enzymatic hydrolysis for 4 h. After the enzymatic hydrolysis is completed, perform enzyme inactivation treatment, solid-liquid separation, and reduce the volume of the liquid phase by vacuum concentration to 1 / 2 of the volume before concentration to obtain the enzymatic hydrolysate;

[0045] (2) Add pepsin (4200 U / g) to the enzymolysis solution, and add pepsin to the enzymolysis solution so that the mass percentage of pepsin is 1.5%. After the addition is completed, stir for 20 min to mix evenly. Then, add threonine and L-lysine under stirring. The added mass of threonine and L-lysine is such that the mass percentage of threonine is 1.5% and the mass percentage of L-lysine is 1%. After the addition is completed, adjust the pH to 5 with citric acid, then stir for 20 min, and then heat in a water bath to 37 °C, keep warm and stir for 5 h. After the stirring is completed, perform enzyme inactivation treatment to obtain a composite solution;

[0046] (3) Mix strawberry granules, blueberry granules and raspberry granules to obtain mixed granules. The mixing mass ratio of strawberry granules, blueberry granules and raspberry granules is strawberry granules: blueberry granules: raspberry granules = 10:5:5. The mixed granules are pulverized and stirred evenly in a stirrer to obtain a pulp solution, and the pulp solution is filtered with gauze. After filtration, it is pasteurized to obtain a mixed berry pulp solution. Mix raw milk, granulated sugar, the composite solution and the mixed berry pulp solution. The mixing ratio of raw milk, granulated sugar, the composite solution and the mixed berry pulp solution is raw milk: granulated sugar: composite solution: mixed berry pulp solution = 100 mL: 7 g: 15 mL: 17 mL. Perform homogenization treatment, inoculate fermentation strains (a mixed fermentation strain of Lactobacillus delbrueckii subsp. bulgaricus and Streptococcus thermophilus in a 1:1 ratio, inoculation amount 0.2% w / v) after pasteurization, ferment at 42 °C for 6 h, and then refrigerate at 4 °C for 10 h to obtain the mixed berry yogurt of this comparative example.

[0047] Comparative Example 2

[0048] A preparation method of a mixed berry yogurt for comparison, the preparation steps include:

[0049] (1) Prepare an aqueous solution of neutral protease (20000 U / g). In the aqueous solution of neutral protease, the mass percentage of neutral protease is 5%. Add soy protein isolate to the aqueous solution of neutral protease. The mass ratio of soy protein isolate to the aqueous solution of neutral protease is soy protein isolate: aqueous solution of neutral protease = 7:100. Stir and mix for 20 min, then heat to 45 °C, and perform constant-temperature enzymolysis for 4 h. After the enzymolysis is completed, perform enzyme inactivation treatment, perform solid-liquid separation, and concentrate the liquid phase under reduced pressure to 1 / 2 of the volume before concentration to obtain an enzymolysis solution. Divide the enzymolysis solution into two equal parts, enzymolysis solution I and enzymolysis solution II;

[0050] (2) Cut the dried shiitake mushrooms into pieces and grind them into powder to obtain shiitake mushroom powder. The shiitake mushroom powder is soaked in deionized water, and the mass ratio of the shiitake mushroom powder soaked in deionized water is shiitake mushroom powder:deionized water = 1:50. Then heat it to 90 °C and keep it warm for extraction for 90 min. After the extraction is completed, perform solid-liquid separation to obtain the extract. Heat the extract in a water bath to 60 °C and keep it warm. Then add the enzymatic hydrolysis solution I to the extract under stirring. The volume ratio of the extract to the enzymatic hydrolysis solution I added to the extract is extract:enzymatic hydrolysis solution I = 4:1. After the addition of the materials is completed, continue to keep it warm and stir at 60 °C for 40 min. After the heat preservation is ended, air-cool it to room temperature to obtain the composite solution I;

[0051] (3) Add pepsin (4200 U / g) to the enzymatic hydrolysis solution II, and add pepsin to the enzymatic hydrolysis solution II so that the mass percentage of pepsin is 1.5%. After the addition of the materials is completed, stir for 20 min to mix evenly. Then adjust the pH to 5 with citric acid, stir for 20 min, and then heat it in a water bath to 37 °C and keep it warm and stir for 5 h. After the stirring is completed, perform enzyme inactivation treatment to obtain the composite solution II of this comparative example;

[0052] (4) Mix strawberry particles, blueberry particles and raspberry particles to obtain mixed particles. The mixing mass ratio of strawberry particles:blueberry particles:raspberry particles = 10:5:5. The mixed particles are crushed and stirred evenly in a stirrer to obtain a fruit pulp solution, and the fruit pulp solution is filtered with gauze. After filtration, perform pasteurization to obtain a mixed berry pulp solution. Mix raw milk, granulated sugar, the composite solution I, the composite solution II, and the mixed berry pulp solution. The mixing ratio of raw milk, granulated sugar, the composite solution I, the composite solution II, and the mixed berry pulp solution is raw milk:granulated sugar:composite solution I:composite solution II:mixed berry pulp solution = 100 mL:7 g:6 mL:9 mL:17 mL. Perform homogenization treatment, and after pasteurization, inoculate with a fermentation strain (a mixed fermentation strain of Lactobacillus delbrueckii subsp. bulgaricus and Streptococcus thermophilus in a ratio of 1:1, inoculation amount 0.2% w / v), ferment at 42 °C for 6 h, and then refrigerate at 4 °C for 10 h to obtain the mixed berry yogurt of this comparative example.

[0053] Comparative Example 3

[0054] A preparation method of a mixed berry yogurt for comparison, and the preparation steps include:

[0055] (1) Prepare an aqueous solution of neutral protease (20000 U / g), in which the mass percentage of neutral protease is 5%. Add soy protein isolate powder to the aqueous solution of neutral protease, and the mass ratio of soy protein isolate powder to the aqueous solution of neutral protease is soy protein isolate powder: aqueous solution of neutral protease = 7:100. Stir and mix for 20 min, then heat to 45 °C and carry out enzymatic hydrolysis at a constant temperature for 4 h. After the enzymatic hydrolysis is completed, inactivate the enzyme, separate the solid and liquid, and concentrate the liquid phase under reduced pressure to 1 / 2 of the volume before concentration to obtain an enzymatic hydrolysate. Divide the enzymatic hydrolysate into two equal-volume parts, namely enzymatic hydrolysate I and enzymatic hydrolysate II;

[0056] (2) Cut dried shiitake mushrooms into small pieces and grind them into powder to obtain shiitake mushroom powder. Soak the shiitake mushroom powder in deionized water, and the mass ratio of shiitake mushroom powder to deionized water is shiitake mushroom powder: deionized water = 1:50. Then heat to 90 °C and keep warm for extraction for 90 min. After the extraction is completed, separate the solid and liquid to obtain an extract. Heat the extract in a water bath to 60 °C and keep warm, then add enzymatic hydrolysate I to the extract under stirring, and the volume ratio of the extract to enzymatic hydrolysate I is extract: enzymatic hydrolysate I = 4:1. After the addition of materials is completed, continue to stir and keep warm at 60 °C for 40 min. After the insulation is completed, air-cool to room temperature to obtain composite liquid I;

[0057] (3) Add pepsin (4200 U / g) to enzymatic hydrolysate II, and add pepsin to enzymatic hydrolysate II so that the mass percentage of pepsin is 1.5%. After the addition of materials is completed, stir for 20 min to mix evenly, then add threonine under stirring, and the added mass of threonine makes the mass percentage of threonine 1.5%. After the addition of materials is completed, adjust the pH to 5 with citric acid, then stir for 20 min, and then heat in a water bath to 37 °C and keep warm and stir for 5 h. After the stirring is completed, inactivate the enzyme to obtain composite liquid II;

[0058] (4) Mix strawberry granules, blueberry granules and raspberry granules to obtain mixed granules. The mixing mass ratio of the strawberry granules, blueberry granules and raspberry granules is strawberry granules: blueberry granules: raspberry granules = 10:5:5. The mixed granules are pulverized and stirred evenly in a stirrer to obtain a fruit pulp solution, and the fruit pulp solution is filtered with gauze, and after filtration, pasteurized to obtain a mixed berry juice. Mix raw milk, granulated sugar, the compound solution I, compound solution II and the mixed berry juice. The mixing ratio of raw milk, granulated sugar, the compound solution I, compound solution II and the mixed berry juice is raw milk: granulated sugar: compound solution I: compound solution II: mixed berry juice = 100 mL: 7 g: 6 mL: 9 mL: 17 mL. Perform homogenization treatment, inoculate fermentation strains (a mixed fermentation strain of Lactobacillus delbrueckii subsp. bulgaricus and Streptococcus thermophilus in a 1:1 ratio, inoculation amount 0.2% w / v) after pasteurization, ferment at 42 °C for 6 h, and then refrigerate at 4 °C for 10 h to obtain the mixed berry yogurt of this comparative example.

[0059] Comparative Example 4

[0060] A preparation method of a mixed berry yogurt for comparison, the preparation steps include:

[0061] (1) Prepare an aqueous solution of neutral protease (20000 U / g). In the aqueous solution of neutral protease, the mass percentage of neutral protease is 5%. Add soy protein isolate to the aqueous solution of neutral protease. The mass ratio of soy protein isolate to the aqueous solution of neutral protease is soy protein isolate: aqueous solution of neutral protease = 7:100. Stir and mix for 20 min, then heat to 45 °C and keep the temperature for enzymatic hydrolysis for 4 h. After enzymatic hydrolysis is completed, inactivate the enzyme, perform solid-liquid separation, and concentrate the liquid phase under reduced pressure to 1 / 2 of the volume before concentration to obtain an enzymatic hydrolysate. Divide the enzymatic hydrolysate into two equal-volume parts, enzymatic hydrolysate I and enzymatic hydrolysate II.

[0062] (2) Cut dried mushrooms into pieces and grind them into powder to obtain mushroom powder. The mushroom powder is soaked in deionized water. The mass ratio of the mushroom powder soaked in deionized water is mushroom powder: deionized water = 1:50. Then heat to 90 °C and keep the temperature for extraction for 90 min. After extraction is completed, perform solid-liquid separation to obtain an extract. Heat the extract in a water bath to 60 °C and keep the temperature, and then add the enzymatic hydrolysate I to the extract under stirring. The volume ratio of the extract to the enzymatic hydrolysate I added to the extract is extract: enzymatic hydrolysate I = 4:1. After adding the materials, continue to stir at 60 °C for 40 min. After the heat preservation is completed, air-cool to room temperature to obtain compound solution I.

[0063] (3) Add pepsin (4200 U / g) to the enzymatic hydrolysate II, and add pepsin to the enzymatic hydrolysate II so that the mass percentage of pepsin is 1.5%. After the feeding is completed, stir for 20 min to mix evenly, and then add L-lysine under stirring. The added mass of L-lysine makes the mass percentage of L-lysine 1%; after the feeding is completed, adjust the pH to 5 with citric acid, then stir for 20 min, then heat in a water bath to 37 °C, keep warm and stir for 5 h, and perform enzyme inactivation treatment after stirring to obtain the composite solution II;

[0064] (4) Mix strawberry granules, blueberry granules and raspberry granules to obtain mixed granules. The mixing mass ratio of strawberry granules: blueberry granules: raspberry granules is strawberry granules: blueberry granules: raspberry granules = 10:5:5; the mixed granules are pulverized and stirred evenly in a stirrer to obtain a pulp solution, and the pulp solution is filtered with gauze, and after filtration, pasteurization is carried out to obtain a mixed berry pulp solution; mix raw milk, granulated sugar, the composite solution I, the composite solution II, and the mixed berry pulp solution. The mixing ratio of raw milk, granulated sugar, the composite solution I, the composite solution II, and the mixed berry pulp solution is raw milk: granulated sugar: composite solution I: composite solution II: mixed berry pulp solution = 100 mL: 7 g: 6 mL: 9 mL: 17 mL; perform homogenization treatment, and after pasteurization, inoculate with a fermentation strain (a mixed fermentation strain of Lactobacillus delbrueckii subsp. bulgaricus and Streptococcus thermophilus in a ratio of 1:1, inoculation amount 0.2% w / v), ferment at 42 °C for 6 h, and then refrigerate at 4 °C for 10 h to obtain the mixed berry yogurt of this comparative example.

[0065] Example 5

[0066] Test the water-holding rate and sensory score of the yogurt prepared by the methods of the above examples and comparative examples. The test method for the water-holding rate is as follows: Weigh the mass of the yogurt to be tested. Place the yogurt to be tested in a centrifuge tube, centrifuge at 2000 r / min for 10 min, let it stand for 30 min, and then pour out the supernatant and weigh the mass of the remaining yogurt. The water-holding rate = the mass of the remaining yogurt / the mass of the yogurt to be tested × 100%. The results are as Figure 1 shown. Select 10 people to score the tissue state, color, taste and smell of the yogurt, and the final data is averaged. The results are shown in Table 1.

[0067]

[0068] Table 1

[0069]

[0070]

[0071] From Table 1 and Figure 1It can be seen that the yogurt prepared by the method of the present invention has a high water holding rate, good tissue morphology, delicate and uniform texture; rich fruit aroma and good taste.

[0072] The technical solutions provided by the present invention have been introduced in detail above. For those of ordinary skill in the art, according to the idea of the embodiments of the present invention, there will be changes in the specific implementation manners and application scopes. In summary, the content of this specification should not be construed as a limitation to the present invention.

Claims

1. A method for preparing a mixed berry yogurt, characterized in that, The preparation steps include: (1) Prepare an aqueous solution of neutral protease. Add soy protein isolate powder to the aqueous solution of neutral protease, stir and mix for more than 20 min, then heat to 45 ± 3 °C, keep the temperature constant for enzymatic hydrolysis for 3 - 5 h. After the enzymatic hydrolysis is completed, inactivate the enzyme, separate the solid and liquid, concentrate the liquid phase under reduced pressure to obtain an enzymatic hydrolysate, and divide the enzymatic hydrolysate into two parts: enzymatic hydrolysate I and enzymatic hydrolysate II; (2) Cut dried shiitake mushrooms into pieces and grind them into powder to obtain shiitake mushroom powder. Soak the shiitake mushroom powder in deionized water, then heat to 90 ± 5 °C and keep warm for extraction for 90 - 150 min. After the extraction is completed, separate the solid and liquid to obtain an extract; Heat the extract in a water bath to 60 ± 3 °C and keep warm, then add the enzymatic hydrolysate I to the extract under stirring. After the addition is completed, continue to keep warm and stir at 60 ± 3 °C for more than 40 min. After the heat preservation is over, air-cool to room temperature to obtain composite liquid I; (3) Add pepsin to the enzymatic hydrolysate II. After the addition is completed, stir for more than 20 min to mix evenly. Then add threonine and L-lysine under stirring. After the addition is completed, adjust the pH to 5 - 5.5, then stir for more than 20 min, and then heat in a water bath to 37 ± 2 °C, keep warm and stir for more than 5 h. After the stirring is completed, inactivate the enzyme to obtain composite liquid II; (4) Mix strawberry granules, blueberry granules and raspberry granules to obtain mixed granules. Crush and stir the mixed granules evenly in a stirrer to obtain a fruit pulp solution. Filter the fruit pulp solution with gauze, and after filtration, perform pasteurization to obtain a mixed berry pulp solution; Mix raw milk, granulated sugar, the composite liquid I, the composite liquid II, and the mixed berry pulp solution, perform homogenization treatment, inoculate fermentation strains after pasteurization, ferment at 42 ± 2 °C for 6 - 7 h, and then refrigerate at 0 - 4 °C for 10 - 12 h to obtain the mixed berry yogurt.

2. The preparation method of a mixed berry yogurt according to claim 1, characterized in that, In the step (1), in the aqueous solution of neutral protease, the mass percentage of neutral protease is 4% - 6%, and the mass ratio of the soy protein isolate powder added to the aqueous solution of neutral protease is soy protein isolate powder: aqueous solution of neutral protease = 5 - 8:

100.

3. The preparation method of a mixed berry yogurt according to claim 1, characterized in that, In the step (1), the enzymatic hydrolysate is divided into two parts: enzymatic hydrolysate I and enzymatic hydrolysate II in equal volume.

4. The preparation method of a mixed berry yogurt according to claim 1, characterized in that, In the step (2), the mass ratio of the shiitake mushroom powder soaked in deionized water is shiitake mushroom powder: deionized water = 1:50 - 100.

5. The preparation method of a mixed berry yogurt according to claim 1, characterized in that, In the step (2), the volume ratio of the extract to which the enzymatic hydrolysate I is added is extract: enzymatic hydrolysate I = 3 - 5:

1.

6. The preparation method of a mixed berry yogurt according to claim 1, wherein, In the step (3), the mass percentage of pepsin added to the enzymatic hydrolysate II is 1.4% - 1.6%, and the added masses of threonine and L-lysine are such that the mass percentage of threonine is 1% - 1.5%, and the mass percentage of L-lysine is 1% - 1.5%.

7. The preparation method of a mixed berry yogurt according to claim 1, characterized in that, In the step (4), the mass ratio of the strawberry granules, blueberry granules and raspberry granules mixed is strawberry granules: blueberry granules: raspberry granules = 10:1 - 10:1 - 10.

8. The preparation method of a mixed berry yogurt according to claim 1, characterized in that, In the step (4), the mixing ratio of raw milk, granulated sugar, the compound liquid I, the compound liquid II, and the mixed berry juice is raw milk: granulated sugar: compound liquid I: compound liquid II: mixed berry juice = 100 mL: 6 - 8 g: 4 - 8 mL: 5 - 10 mL: 15 - 18 mL.

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