A method for preparing a phosphate ester starch for yogurt and a yogurt

Abstract

The application discloses a preparation method of phosphate ester starch for yogurt and the yogurt, and mainly relates to the technical field of yogurt. The method comprises the following steps: S1, obtaining a phytase hydrolysate by decomposing a phytic acid solution based on phytase; S2, adding 200-500 mL of the phytase hydrolysate in 10-50 g of cassava starch to prepare a starch suspension; S3, adjusting the pH of the starch suspension to be alkaline, and adding 15-20 U / g of hexokinase based on water bath heating at 40-55 DEG C, and continuously reacting for 10-14 h to perform a phosphorylation reaction; and S4, after the reaction is completed, obtaining enzyme-modified starch by centrifugation, water washing, drying and grinding. The application has the beneficial effects that the preparation process is simple, safe, pollution-free and low in production cost, the application plays a good thickening and stabilizing role, and the shelf life of the yogurt product is effectively prolonged.

Description

Technical Field

[0001] This invention relates to the field of yogurt technology, specifically a method for preparing phosphate starch for yogurt and yogurt. Background Technology

[0002] Yogurt is a food produced by fermenting milk with Lactobacillus bulgaricus and Streptococcus thermophilus. This fermentation process converts lactose in milk into lactic acid, giving yogurt its sour taste and rich texture. However, various quality defects are frequently observed during the production, transportation, and storage of yogurt, such as poor viscosity, coarse texture, decreased mouthfeel, whey separation, and tissue breakage.

[0003] Starch, due to its gelatinization and retrogradation properties, has various applications in the food industry, such as as a stabilizer, gelling thickener, binder, and water-retaining agent. However, natural starch has significant limitations, including a high tendency to retrograde, poor thermal stability, low shear strength, insolubility in water, rapid retrogradation, dehydration shrinkage, and poor thermal properties, thus restricting its application in the food industry. To improve starch properties and expand its application range, starch is modified using external methods based on its original characteristics to obtain modified starch with desired properties. The presence of numerous reactive hydroxyl groups and simple glycosidic bonds in the starch molecular chain provides a structural basis for starch modification, allowing for easy physical, chemical, enzymatic, or combined modifications. Chemical modification is the most widely used in the industry due to its cost-effectiveness and simplicity, typically involving altering the hydroxyl groups at the C2, C3, and C6 positions of the starch molecule through esterification, etherification, and oxidation. However, traditional chemical methods have potential hazards; therefore, environmentally friendly methods can be used to modify starch properties.

[0004] Modified starch, obtained through physical, chemical, or enzymatic treatment, alters the original natural properties of starch, effectively compensating for the deficiencies of natural starch and significantly improving its performance in yogurt processing. Therefore, modified starch is commonly used in yogurt preparation to enhance viscosity, improve texture, increase yogurt solids, and prevent whey separation. Furthermore, compared to other hydrocolloids, modified starch is the preferred thickener for yogurt due to its creamy texture and ease of processing.

[0005] Compared to native starch, phosphate starch gelatinizes more easily, resulting in significantly improved transparency and viscosity, enhanced stability, reduced sedimentation, and good freeze-thaw stability. When used in yogurt, this type of starch can stabilize and improve the yogurt's texture, reduce excessive whey separation, provide excellent thickening and stabilizing effects, and effectively extend the shelf life of yogurt products.

[0006] However, existing methods for preparing phosphate starch mostly employ chemical modification, which suffers from problems such as chemical reagent residues, significant pollution during the reaction process, and difficulty in ensuring product safety. Enzymatic modification, as a green alternative, still has drawbacks including complex processes, low modification efficiency, and high costs. Therefore, developing a green, safe, and efficient method for preparing phosphate starch to better improve yogurt quality remains a pressing technical problem to be solved in this field. Summary of the Invention

[0007] The purpose of this invention is to provide a method for preparing phosphate starch for yogurt and the yogurt itself. The preparation process is simple, safe and pollution-free, and has low production cost. It plays a good role in thickening and stabilizing and effectively extends the shelf life of yogurt products.

[0008] To achieve the above objectives, the present invention employs the following technical solution: A method for preparing phosphate starch for yogurt includes the following steps: S1, based on the decomposition of phytic acid solution by phytase, phytase hydrolysate is obtained; S2, add 200-500mL of phytase hydrolysate to 10-50g of cassava starch to make a starch suspension; S3, adjust the pH of the starch suspension to alkaline, and add 15-20 U / g of hexokinase based on water bath heating at 40-55℃, continuing the reaction for 10-14 hours to carry out the phosphorylation reaction. After the reaction in S4 is complete, enzyme-modified starch is obtained by centrifugation, washing with water, drying, and grinding.

[0009] Step S1 includes preparing a 2% phytic acid solution, adjusting the pH of the solution to 4-6, placing it in a water bath at 30-60℃, adding 400-1200 u / g of phytase, and reacting for 0.5-2 h. Then, it is inactivated in a 95℃ water bath for 25 min.

[0010] The centrifugation, washing, and drying in step S4 are as follows: centrifuge at 5000 rpm for 5 min, discard the supernatant, add 3 times the volume of ultrapure water to wash the precipitate, wash and centrifuge 3 times, and then dry the precipitate in an oven at 40℃ for 48 h.

[0011] As a preferred solution, the following steps are included: S1, prepare a phytic acid solution with a concentration equal to that of a method for preparing phosphate starch for yogurt, adjust the pH of the solution to 5, and place it in a water bath at 50℃. Add 1000 u / g phytase, react for 1 h, and then inactivate it in a water bath at 95℃ for 25 min; S2, Weigh 20g of cassava starch and add 250ml of phytase hydrolysate; S3, adjust the pH of the starch suspension to 9, place it in a water bath at 50℃, add 20 U / g hexokinase, and continue the reaction for 12 hours; S4, the enzymatic hydrolysate was centrifuged at 5000 rpm for 5 min, the supernatant was discarded, and 3 times the volume of ultrapure water was added to wash the precipitate. After washing and centrifuging 3 times, the precipitate was dried in an oven at 40℃ for 48 h and then ground to obtain enzyme-modified starch.

[0012] In practical applications, enzyme-modified starch is added to the raw materials before fermentation. After preheating, homogenization, and pasteurization, fermentation yields yogurt.

[0013] As another aspect of the present invention, the above-mentioned enzyme-modified starch is added to the raw materials before fermentation, and after preheating, homogenization and pasteurization, yogurt is obtained by fermentation.

[0014] Furthermore, it is obtained through the following steps: Weigh 10-30g of whole milk powder, add 0.5-2.0g of enzyme-modified starch, then add 100-200ml of ultrapure water, and preheat at 60-80℃ for 30 minutes; Homogenize at 15-30 MPa, then pasteurize at 95°C for 10 min; The sample is cooled to 40°C, inoculated with direct-inoculation culture, and fermented at 40°C for 6-10 hours to obtain yogurt.

[0015] As the optimal solution, the following steps are performed: Weigh 20g of whole milk powder, add 1.5g of enzyme-modified starch, and then add 100ml of ultrapure water. Preheat at 65℃ for 30min; homogenize at 20MPa, and then pasteurize at 95℃ for 10min; cool the sample to 40℃, inoculate with direct-inoculation culture, and ferment at 40℃ for 10h to obtain yogurt.

[0016] The bacterial strains are Lactobacillus bulgaricus and Streptococcus thermophilus.

[0017] After fermentation is complete, store at 4°C for 12-24 hours.

[0018] Compared with the prior art, the beneficial effects of the present invention are as follows: This invention utilizes phytase to hydrolyze phytic acid; then, hexokinase is used to introduce phosphate groups onto the hydroxyl groups of starch. The prepared phosphate starch exhibits good paste viscosity and freeze-thaw stability. Furthermore, the preparation process is simple, environmentally friendly, safe, and requires minimal equipment. Applying this starch to yogurt improves its texture properties, such as firmness, cohesiveness, and viscosity. It can also reduce whey separation in yogurt. Attached Figure Description

[0019] Figure 1 This is a graph showing the starch RVA gelatinization curve. Figure 2 The image shows the appearance of whey separation after centrifugation of yogurt (5000 r / min, 20 min). Detailed Implementation

[0020] The present invention will be further illustrated below with reference to specific embodiments. It should be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of the invention. Furthermore, it should be understood that after reading the teachings of this invention, those skilled in the art can make various alterations or modifications to the invention, and these equivalent forms also fall within the scope defined in this application.

[0021] Unless otherwise specified, the instruments, reagents, and materials used in the following embodiments are all conventional instruments, reagents, and materials already available in the prior art and can be obtained through legitimate commercial channels. Unless otherwise specified, the experimental methods and detection methods used in the following embodiments are all conventional experimental methods and detection methods already available in the prior art. Example 1

[0022] (1) Prepare a phytic acid solution of a certain concentration, adjust the pH of the solution to 5, and place it in a water bath at 50℃. Add 1000u / g phytase and react for 1h. Then inactivate it in a water bath at 95℃ for 25min.

[0023] (2) Weigh 20g of cassava starch and add 250ml of phytase hydrolysate.

[0024] (3) Adjust the pH of the starch suspension to 9, place it in a water bath at 50°C, add 20 U / g of hexokinase, and continue the reaction for 12 hours.

[0025] (4) The final enzymatic hydrolysate was centrifuged at 5000 rpm for 5 min. After discarding the supernatant, 3 times the volume of ultrapure water was added to wash the precipitate. After washing and centrifuging 3 times, the precipitate was dried in an oven at 40℃ for 48 h.

[0026] (5) Weigh 20g of whole milk powder, add 1.5g of modified starch, then add 100ml of ultrapure water, preheat at 65℃ for 30min, homogenize at 20MPa, and pasteurize at 95℃ for 10min. Cool the sample to 40℃, inoculate with direct-inoculation culture, and ferment at 40℃ for 10h. Finally, store at 4°C for 24 hours.

[0027] The enzyme-modified starch prepared in this example had a peak viscosity of 4105.33±21.01 cP and a freeze-thaw water separation rate of 25.26±0.02%. The native starch had a peak viscosity of 3538.33±21.01 cP and a freeze-thaw water separation rate of 35.22±0.02%. The commercially available phosphate starch had a peak viscosity of 3974.67±50.00 cP and a freeze-thaw water separation rate of 27.91±0.03%. The enzyme-modified starch had a higher peak viscosity and better freeze-thaw stability than both the native starch and the commercially available starch. When the enzyme-modified starch was added to yogurt, the textural properties of the yogurt were measured. The yogurt hardness was 26.33±0.29 g, the cohesiveness was 0.76±0.01, and the viscosity was 11.33±0.29 g. It also reduced whey separation in the yogurt, and the water holding capacity of the yogurt was measured to be 89.61±0.03%.

[0028] Commercially available phosphate starch was added to yogurt, and the yogurt's hardness was measured to be 21.00±0.87g, its cohesiveness to be 0.67±0.01, and its viscosity to be 10.07±0.12g. The yogurt's water holding capacity was 85.62±0.01%. This indicates that enzyme-modified starch can improve the properties of yogurt. Example 2

[0029] (1) Prepare a phytic acid solution of a certain concentration, adjust the pH of the solution to 5, and place it in a water bath at 50℃. Add 1000 u / g phytase and react for 1 h. Then inactivate it in a water bath at 95℃ for 25 min; (2) Weigh 20g of cassava starch and add 300ml of phytase hydrolysate; (3) Adjust the pH of the starch suspension to 9, place it in a water bath at 40°C, add 10 U / g of hexokinase, and continue the reaction for 12 hours.

[0030] (4) The final enzymatic hydrolysate was centrifuged at 5000 rpm for 5 min. After discarding the supernatant, 3 times the volume of ultrapure water was added to wash the precipitate. After washing and centrifuging 3 times, the precipitate was dried in an oven at 40℃ for 48 h.

[0031] (5) Weigh 20g of whole milk powder, add 0.5g of starch, then add 150ml of ultrapure water, preheat at 60℃ for 30min, homogenize at 20 MPa, and pasteurize at 95℃ for 10min. Cool the sample to 40℃, inoculate with direct-inoculation culture, and ferment at 40℃ for 10h. Finally, store at 4°C for 24 hours.

[0032] The modified starch prepared in this example had a peak viscosity of 3669.00±12.29 cP and a freeze-thaw water separation rate of 29.79±0.03%. When added to yogurt, the textural properties of the yogurt were measured: hardness was 17.93±0.12 g, cohesiveness was 0.71±0.01, and viscosity was 7.87±0.12 g. It also reduced whey separation in yogurt, with a water holding capacity of 80.59±0.21%. Example 3

[0033] (1) Prepare a phytic acid solution of a certain concentration, adjust the pH of the solution to 5, and place it in a water bath at 50℃. Add 1000 u / g phytase and react for 1 h. Then inactivate it in a water bath at 95℃ for 25 min; (2) Weigh 20g of cassava starch and add 300ml of phytase hydrolysate; (3) Adjust the pH of the starch suspension to 9, place it in a water bath at 40°C, add 15 U / g of hexokinase, and continue the reaction for 12 hours.

[0034] (4) The final enzymatic hydrolysate was centrifuged at 5000 rpm for 5 min. After discarding the supernatant, 3 times the volume of ultrapure water was added to wash the precipitate. After washing and centrifuging 3 times, the precipitate was dried in an oven at 40℃ for 48 h.

[0035] (5) Weigh 20g of whole milk powder, add 0.5g of starch, then add 150ml of ultrapure water, preheat at 60℃ for 30min, homogenize at 20 MPa, and pasteurize at 95℃ for 10min. Cool the sample to 40℃, inoculate with direct-inoculation culture, and ferment at 40℃ for 10h. Finally, store at 4°C for 24 hours.

[0036] The modified starch prepared in this example had a peak viscosity of 3770.67±13.05 cP and a freeze-thaw water separation rate of 27.11±0.04%. When added to yogurt, the textural properties of the yogurt were measured: hardness was 20.33±0.58 g, cohesiveness was 0.77±0.02, and viscosity was 9.83±0.29 g. It also reduced whey separation in yogurt, with a water holding capacity of 27.11±0.04%.

[0037] Example 4: Comparative Example 1 (1) Prepare a phytic acid solution of a certain concentration, adjust the pH of the solution to 5, and place it in a water bath at 50℃. Add 1000u / g phytase and react for 1h. Then inactivate it in a water bath at 95℃ for 25min.

[0038] (2) Weigh 20g of cassava starch and add 250ml of phytase hydrolysate.

[0039] (3) Adjust the pH of the starch suspension to 9, place it in a water bath at 50°C, add 20 U / g of hexokinase, and continue the reaction for 12 hours.

[0040] (4) The final enzymatic hydrolysate was centrifuged at 5000 rpm for 5 min. After discarding the supernatant, 3 times the volume of ultrapure water was added to wash the precipitate. After washing and centrifuging 3 times, the precipitate was dried in an oven at 40℃ for 48 h.

[0041] (5) Weigh 20g of whole milk powder, add 0g of modified starch, then add 100ml of ultrapure water, preheat at 65℃ for 30min, homogenize at 20MPa, and pasteurize at 95℃ for 10min. Cool the sample to 40℃, inoculate with direct-inoculation culture, and ferment at 40℃ for 10h. Finally, store at 4°C for 24 hours.

[0042] The modified starch prepared in this example had a peak viscosity of 4105.33±13.28 cP and a freeze-thaw water separation rate of 25.26±0.02%. When added to yogurt, the textural properties of the yogurt were measured: hardness was 17.17±0.29 g, cohesiveness was 0.70±0.03, and viscosity was 8.33±0.29 g. It also reduced whey separation in yogurt, with a water holding capacity of 76.87±0.03%.

[0043] Example 5: Comparative Example 1 (1) Prepare a phytic acid solution of a certain concentration, adjust the pH of the solution to 5, and place it in a water bath at 50℃. Add 1000u / g phytase and react for 1h. Then inactivate it in a water bath at 95℃ for 25min.

[0044] (2) Weigh 20g of cassava starch and add 250ml of phytase hydrolysate.

[0045] (3) Adjust the pH of the starch suspension to 9, place it in a water bath at 50°C, add 20 U / g of hexokinase, and continue the reaction for 12 hours.

[0046] (4) The final enzymatic hydrolysate was centrifuged at 5000 rpm for 5 min. After discarding the supernatant, 3 times the volume of ultrapure water was added to wash the precipitate. After washing and centrifuging 3 times, the precipitate was dried in an oven at 40℃ for 48 h.

[0047] (5) Weigh 20g of whole milk powder, add 1.0g of modified starch, then add 100ml of ultrapure water, preheat at 65℃ for 30min, homogenize at 20MPa, and pasteurize at 95℃ for 10min. Cool the sample to 40℃, inoculate with direct-inoculation culture, and ferment at 40℃ for 10h. Finally, store at 4°C for 24 hours.

[0048] The modified starch prepared in this example had a peak viscosity of 4105.33±13.28 cP and a freeze-thaw water separation rate of 25.26±0.02%. When added to yogurt, the textural properties of the yogurt were measured: hardness was 22.33±0.29 g, cohesiveness was 0.77±0.06, and viscosity was 11.17±0.29 g. It also reduced whey separation in yogurt, with a water holding capacity of 85.32±0.01%.

[0049] Table 1 shows the peak viscosity and freeze-thaw separation rate of starch.

[0050] Table 2 shows the determination of relevant properties of yogurt after adding starch.

[0051] This invention utilizes phytase to hydrolyze the phosphate groups in phytic acid molecules stepwise, yielding inositol and phosphate as the final products. Hexokinase and tapioca starch are then added to prepare phosphate ester starch. This is a green, enzyme-modified preparation method. The resulting enzyme-modified starch exhibits paste viscosity and freeze-thaw stability close to or better than commercially available starches. Adding this enzyme-modified starch to yogurt improves its texture and reduces whey separation, with effects comparable to commercially available starches. This process is simple, safe, and provides stable performance.

[0052] Example 6: (1) Prepare a 2% phytic acid solution, adjust the pH of the solution to 4, and place it in a water bath at 30℃. Add 400 u / g phytase and react for 1 h. Then inactivate it in a water bath at 95℃ for 25 min.

[0053] (2) Weigh 10g of cassava starch and add 200ml of phytase hydrolysate.

[0054] (3) Adjust the pH of the starch suspension to 8, place it in a water bath at 40°C, add 15 U / g of hexokinase, and continue the reaction for 10 h.

[0055] (4) The final enzymatic hydrolysate was centrifuged at 5000 rpm for 5 min. After discarding the supernatant, 3 times the volume of ultrapure water was added to wash the precipitate. After washing and centrifuging 3 times, the precipitate was dried in an oven at 40℃ for 48 h.

[0056] (5) Weigh 10g of whole milk powder, add 0.5g of modified starch, then add 100ml of ultrapure water, preheat at 60℃ for 30min, homogenize at 15MPa, and pasteurize at 95℃ for 10min. Cool the sample to 40℃, inoculate with direct-inoculation culture, and ferment at 40℃ for 6h. Finally, store at 4°C for 12 hours.

[0057] The modified starch prepared in this example had a peak viscosity of 3656.50±45.96 cP and a freeze-thaw water separation rate of 28.37±1.05%. When added to yogurt, the textural properties of the yogurt were measured: hardness was 16.33±0.29 g, cohesiveness was 0.69±0.02, and viscosity was 8.17±0.28 g. It also reduced whey separation in yogurt, with a water holding capacity of 80.24±0.02%.

[0058] Example 7: (1) Prepare a 2% phytic acid solution, adjust the pH of the solution to 6, and place it in a water bath at 60℃. Add 1200 u / g phytase and react for 1 h. Then inactivate it in a water bath at 95℃ for 25 min.

[0059] (2) Weigh 50g of cassava starch and add 500ml of phytase hydrolysate.

[0060] (3) Adjust the pH of the starch suspension to 9.5, place it in a water bath at 55°C, add 20 U / g of hexokinase, and continue the reaction for 14 hours.

[0061] (4) The final enzymatic hydrolysate was centrifuged at 5000 rpm for 5 min. After discarding the supernatant, 3 times the volume of ultrapure water was added to wash the precipitate. After washing and centrifuging 3 times, the precipitate was dried in an oven at 40℃ for 48 h.

[0062] (5) Weigh 30g of whole milk powder, add 2.0g of modified starch, then add 200ml of ultrapure water, preheat at 80℃ for 30min, homogenize at 30MPa, and pasteurize at 95℃ for 10min. Cool the sample to 40℃, inoculate with direct-inoculation culture, and ferment at 40℃ for 10h. Finally, store at 4°C for 24 hours.

[0063] The modified starch prepared in this example had a peak viscosity of 3757.33±34.85 cP and a freeze-thaw water separation rate of 27.05±0.17%. When added to yogurt, the textural properties of the yogurt were measured: hardness was 19.17±0.28 g, cohesiveness was 0.81±0.02, and viscosity was 8.33±0.28 g. It also reduced whey separation in yogurt, with a water holding capacity of 82.69±0.01%.

Claims

1. A green process for the preparation of a phosphated starch for yoghurt, characterized in that, Includes the following steps: S1, based on the decomposition of phytic acid solution by phytase, phytase hydrolysate is obtained; S2, add 200-500mL of phytase hydrolysate to 10-50g of cassava starch to make a starch suspension; S3, adjust the pH of the starch suspension to alkaline, and add 15-20 U / g of hexokinase based on water bath heating at 40-55℃, continuing the reaction for 10-14 hours to carry out the phosphorylation reaction. After the reaction in S4 is complete, enzyme-modified starch is obtained by centrifugation, washing with water, drying, and grinding.

2. The method for preparing phosphate starch for yogurt according to claim 1, characterized in that, Step S1 includes preparing a 2% phytic acid solution, adjusting the pH of the solution to 4-6, placing it in a water bath at 30-60℃, adding 400-1200 u / g of phytase, and reacting for 0.5-2 h. Then, it is inactivated in a 95℃ water bath for 25 min.

3. The method for preparing phosphate starch for yogurt according to claim 1, characterized in that, The centrifugation, washing, and drying in step S4 are as follows: centrifuge at 5000 rpm for 5 min, discard the supernatant, add 3 times the volume of ultrapure water to wash the precipitate, wash and centrifuge 3 times, and then dry the precipitate in an oven at 40℃ for 48 h.

4. The method for preparing phosphate starch for yogurt according to claim 1, characterized in that, Includes the following steps: S1. Prepare a 2% phytic acid solution, adjust the pH to 5, and place it in a water bath at 50℃. Add 1000 u / g phytase, react for 1 h, and then inactivate it in a water bath at 95℃ for 25 min. S2, Weigh 20g of cassava starch and add 250ml of phytase hydrolysate; S3, adjust the pH of the starch suspension to 9, place it in a water bath at 50℃, add 20 U / g hexokinase, and continue the reaction for 12 hours; S4, the enzymatic hydrolysate was centrifuged at 5000 rpm for 5 min, the supernatant was discarded, and 3 times the volume of ultrapure water was added to wash the precipitate. After washing and centrifuging 3 times, the precipitate was dried in an oven at 40℃ for 48 h and then ground to obtain enzyme-modified starch.

5. The method for preparing phosphate starch for yogurt according to claim 1, characterized in that, In practical applications, enzyme-modified starch is added to the raw materials before fermentation. After preheating, homogenization, and pasteurization, fermentation yields yogurt.

6. A type of yogurt, characterized in that, The enzyme-modified starch according to any one of claims 1-5 is added to the raw materials before fermentation, and after preheating, homogenization, and pasteurization, fermentation yields yogurt.

7. The yogurt according to claim 6, characterized in that, It is prepared through the following steps: Weigh 10-30g of whole milk powder, add 0.5-2.0g of enzyme-modified starch as described in any one of claims 1-5, then add 100-200ml of ultrapure water, and preheat at 60-80℃ for 30min; Homogenize at 15-30 MPa, then pasteurize at 95°C for 10 min; The sample is cooled to 40°C, inoculated with direct-inoculation culture, and fermented at 40°C for 6-10 hours to obtain yogurt.

8. The yogurt according to claim 6, characterized in that, The yogurt was prepared by the following steps: 20g of whole milk powder was weighed, 1.5g of enzyme-modified starch as described in any one of claims 1-5 was added, and 100ml of ultrapure water was added. The mixture was preheated at 65℃ for 30min; homogenized at 20MPa, and then pasteurized at 95℃ for 10min; the sample was cooled to 40℃, inoculated with direct-inoculation culture, and fermented at 40℃ for 10h to obtain yogurt.

9. A yogurt according to claim 7 or 8, characterized in that, The bacterial strains are Lactobacillus bulgaricus and Streptococcus thermophilus.

10. The yogurt according to claim 6, characterized in that, After fermentation is complete, store at 4°C for 12-24 hours.

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