Modified potato resistant starch and its use in set yoghurt

Abstract

The application discloses modified potato resistant starch and application thereof in set yogurt, and comprises the following steps: adding chitosan oligosaccharide and zinc salt into potato PRS3 starch milk, mixing and treating, reacting with leucine-glycine dipeptide to obtain composite modified potato PRS3 starch; pre-gelatinizing the composite modified potato PRS3 starch, mixing with milk, mixing, homogenizing, sterilizing, inoculating and fermenting, and post-ripening to prepare set yogurt. 2+ The chitosan oligosaccharide-Zn 2+ and leucine-glycine dipeptide composite modified potato PRS3 starch forms a reversible three-dimensional coordination network and hydrophobic interaction, significantly improves transparency, freeze-thaw stability and resistance retention rate, and enhances the adsorption and combination capacity of milk protein and milk fat. The set yogurt has good gel strength, texture characteristics and sensory quality, effectively promotes the proliferation of probiotics, improves the coagulation efficiency, prevents whey separation and promotes the synthesis of intestinal short-chain fatty acids, and improves intestinal health.

Description

Technical Field

[0001] This invention belongs to the field of food processing technology, specifically relating to a modified potato resistant starch and its application in set-type yogurt. Background Technology

[0002] Potato starch is rich in starch and has advantages such as large particle size, high viscosity, low gelatinization temperature, strong water absorption, and high paste transparency, giving it high economic value and development potential. Resistant starch (RS) refers to starch and its breakdown products that are not absorbed by the healthy human small intestine. It has physiological functions similar to dietary fiber. Studies have shown that adding resistant starch to the diet can inhibit postprandial blood glucose rise, lower serum cholesterol levels, and promote the proliferation of beneficial bacteria such as lactobacilli and bifidobacteria, thus improving the intestinal microecological environment.

[0003] Resistant starch can be classified into five types: RS1, RS2, RS3, RS4, and RS5. RS3 resistant starch (also known as retrograde resistant starch) is formed by rearranging starch molecules through relevant treatments, exhibiting good thermal stability and processing adaptability. In recent years, RS3 starch has been used as a prebiotic and thickening stabilizer in fermented dairy products. However, in existing studies, it is mostly used as a stabilizer in small quantities, thus failing to provide sufficient dietary fiber. Furthermore, RS3 starch has lower transparency and water-holding capacity compared to native potato starch, limiting its application in high-dose fermented dairy products. Current technologies for improving the properties of RS3 starch often employ physical modifications such as ultrasound and radio frequency or chemical methods such as octenyl succinic anhydride esterification. However, improving these properties often requires inhibiting retrogradation or disrupting crystallization, leading to a decrease in resistance content. Therefore, it is urgent to develop methods suitable for maintaining the original health functions and processing characteristics of PRS3, to solve the problems of low transparency and reduced water retention, and to prepare modified potato RS3 starch that is more suitable for set-type yogurt, so as to better improve the quality and efficacy of potato resistant starch set-type yogurt. Summary of the Invention

[0004] Technical Problem to be Solved: To address the aforementioned technical problems, the present invention aims to disclose a method for preparing modified potato resistant starch set-type yogurt. This method includes adding chitosan oligosaccharide and zinc salt to potato PRS3 starch milk for mixing and treatment, followed by reaction with leucine-glycine dipeptide to obtain composite modified potato PRS3 starch. The composite modified potato PRS3 starch is pre-gelatinized and mixed with milk, then subjected to mixing, homogenization sterilization, inoculation fermentation, and post-maturation to produce set-type yogurt. This invention utilizes chitosan oligosaccharide-Zn²⁺ and leucine-glycine dipeptide composite modified potato PRS3 starch to form a reversible three-dimensional coordination network and hydrophobic interactions, significantly improving transparency, freeze-thaw stability, and resistance retention rate, and enhancing the adsorption and binding capacity for milk proteins and milk fats. The set-type yogurt of this invention has good gel strength, textural properties, and sensory quality, effectively promoting probiotic proliferation, improving curdling efficiency, preventing whey separation, promoting the synthesis of short-chain fatty acids in the intestine, and improving intestinal health.

[0005] Technical solution: A method for preparing modified potato resistant starch-based yogurt, comprising the following steps: S1. Preparation of composite modified potato PRS3 starch Chitosan oligosaccharide and zinc salt were added to potato PRS3 starch milk and mixed, then reacted with leucine-glycine dipeptide solution, and finally dried to obtain composite modified potato PRS3 starch. S2. Preparation of modified potato resistant starch coagulating yogurt The modified potato PRS3 starch was pregelatinized and mixed with milk. After adding auxiliary materials, it was homogenized, sterilized, inoculated, fermented, and then matured to produce potato resistant starch set yogurt.

[0006] Preferably, in S1, the mass fraction of potato PRS3 starch milk is 15-30%, the amount of chitosan oligosaccharide added is 1-8%, and the amount of zinc salt added is 0.1-1%, based on the mass of potato PRS3 starch; the zinc salt is zinc chloride, zinc lactate, or zinc gluconate.

[0007] Preferably, the mass concentration of the leucine-glycine dipeptide solution in S1 is 2-10%, and the volume ratio of the leucine-glycine dipeptide solution to the potato PRS3 starch milk is 1:(2-5).

[0008] Preferably, the leucine-glycine dipeptide is prepared by mixing and dissolving leucine methyl ester and glycine in a molar ratio of 1:(0.6-1.5), adding α-amino acid ester acyltransferase and treating for 1-3 hours at 25-30℃ and pH 8.0-9.0, followed by enzyme inactivation at 45-60℃ for 20-30 minutes and purification.

[0009] Preferably, the amount of compound modified potato PRS3 starch added in S2 is 3-6%; the excipients consist of 0.4-0.6% xylitol, 0.006-0.01% acesulfame potassium and 0.0008-0.0012% neotame; more preferably, the excipients consist of 0.6% xylitol, 0.01% acesulfame potassium and 0.0008% neotame.

[0010] Preferably, the homogenization sterilization conditions in S2 are: homogenization pressure 15-25 MPa, homogenization time 10-15 min, sterilization temperature 85-95℃, and sterilization time 5-10 min.

[0011] Preferably, the inoculation and fermentation conditions in S2 are: 5-8% inoculum amount, 38-44℃ fermentation temperature, and 8-11h fermentation time; the inoculum is composed of Lactobacillus bulgaricus, Streptococcus thermophilus, Lactobacillus paracasei, Lactobacillus acidophilus, and Bifidobacterium animalis in a ratio of 1:1:(1-3):1:1; more preferably, the inoculum amount is 7%, the fermentation temperature is 42℃, and the fermentation time is 10h, the inoculum is composed of Lactobacillus bulgaricus, Streptococcus thermophilus, Lactobacillus paracasei, Lactobacillus acidophilus, and Bifidobacterium animalis in a ratio of 1:1:2:1:1.

[0012] Preferably, the post-ripening conditions in S2 are a processing temperature of 2-6℃ and a post-ripening time of 20-25h. Beneficial effects

[0013] 1. This invention uses amino oligosaccharide-Zn 2+ And a dipeptide-modified potato PRS3 starch synthesized from leucine and glycine, Zn 2+The modified structure forms a reversible and loose three-dimensional coordination network with the protonated amino groups on the oligosaccharide and the abundant hydroxyl groups on the potato PRS3 starch molecular chain, avoiding excessive aggregation between starch molecules or the formation of dense gel clumps, thereby reducing light scattering and improving the transparency of potato PRS3 starch. During the freeze-thaw cycle, the reversible coordination bonds generated by the modification can moderately shrink the network during freezing without destroying the coordination sites, and the network quickly returns to its original state during thawing, thereby effectively inhibiting the mechanical damage of ice crystals to the structure of potato PRS3 starch, preventing dehydration shrinkage and water separation, and significantly reducing freeze-thaw water separation to improve freeze-thaw stability. When a dipeptide synthesized from leucine and glycine is mixed with potato PRS3 starch treated with amino oligosaccharide-Zn²⁺, its leucine side chain can insert into the hydrophobic cavity of the double helix structure of potato PRS3 starch and the hydrophobic region of the starch molecule chain. This hydrophobic interaction disturbs the ordered structure of the tightly crystalline region of potato PRS3 starch, reducing excessive crystallinity and thus inhibiting long-term retrogradation during storage. Simultaneously, the amino and carboxyl groups of glycine can form a broad hydrogen bond network with the hydroxyl groups on the starch chain, the amino groups on the oligosaccharide, and water molecules, enhancing the hydration capacity of potato PRS3 starch and improving its water-holding capacity. Furthermore, its hydrophobic end is anchored to the starch chain, while its hydrophilic end coordinates with the amino groups or Zn²⁺ in the amino oligosaccharide-Zn²⁺ coordination network. 2+ The interaction between the coordinated water layer and the starch enhances the organic connection between potato PRS3 starch and the amino oligosaccharide coordination bridging network. The small molecule flexible structure of the dipeptide allows it to diffuse freely into the inter-chain gaps of starch, thereby preventing the formation of excessive coarse crystals in the amorphous region of starch during the rearrangement of starch molecules. This promotes the rearrangement to form a more regular crystal form with stronger resistance to enzymatic hydrolysis, and further synergistically improves the freeze-thaw stability, transparency and resistance retention rate of potato PRS3 starch.

[0014] 2. This invention uses composite modified potato PRS3 starch to prepare set-type yogurt. The three-dimensional coordination network in the composite modified potato PRS3 starch forms a stable cationic microenvironment around the starch molecules. This microenvironment can electrostatically attract casein in milk, causing casein to be adsorbed onto the surface and internal pores of the starch network. This prevents free casein from agglomerating and precipitating due to charge repulsion, thus avoiding its impact on the yogurt's texture. Furthermore, the high porosity of the coordination network allows whey protein, casein, and small-molecule lactose to freely permeate and be physically retained, maintaining efficient and stable milk absorption capacity. Simultaneously, Zn... 2+ It can cross-link with the phosphate groups on the milk fat globule membrane, making the fat globules uniformly dispersed. The hydrophobic end of leucine-glycine is inserted into the hydrophobic region of the starch double helix to improve the affinity of potato PRS3 starch surface for milk fat, significantly enhancing the adsorption capacity and binding strength of potato PRS3 starch for milk protein, thereby achieving the purpose of efficient absorption and stable binding of milk protein and milk fat.

[0015] 3. This invention uses modified potato PRS3 starch and milk as raw materials to prepare set-type yogurt through probiotic fermentation. The modified potato PRS3 starch and amino oligosaccharides can promote the proliferation of probiotics and encourage probiotics and casein to actively accumulate around the starch network, improving the coagulation ability of probiotics and shortening the coagulation time. Moreover, the coordination network locks in a large amount of free water through hydrogen bonds and capillary action, which can prevent moisture loss during fermentation, acidification, and refrigeration, and better prevent whey separation, thus giving the yogurt good sensory quality. The modified potato PRS3 starch can combine with milk protein through multiple interactions to form a uniform and dense three-dimensional composite gel network, giving the yogurt good gel strength and textural properties, ensuring that the yogurt maintains good quality during storage. In vitro fecal fermentation model tests show that the potato resistant starch set-type yogurt prepared by the method of this invention can promote the synthesis of short-chain fatty acids in the human intestine and enhance the intestinal health function of the yogurt. Attached Figure Description

[0016] Figure 1 The textural properties of Example 7, Comparative Examples 4-7, and regular yogurt during storage are shown, where A represents consistency, B represents hardness, C represents cohesiveness, and D represents cohesiveness. Figure 2 The acidity, water-holding capacity, and gel strength of Example 7, Comparative Examples 4-7, and regular yogurt during storage are shown, where A represents gel strength, B represents acidity, and C represents water-holding capacity. Figure 3 Examples 7, Comparative Examples 4-7, and regular yogurt are shown to show the survival of lactic acid bacteria during storage, where A represents the total number of lactic acid bacteria and B represents the number of bifidobacteria. Detailed Implementation

[0017] The present invention will be further described below with reference to embodiments. These embodiments are illustrative of the present invention, but the present invention is not limited to these embodiments: Example 1

[0018] A method for preparing composite modified potato PRS3 starch includes the following steps: Step 1. Mix 7.35g leucine methyl ester hydrochloride and 2.25g glycine, add 100mL 0.1mol / L phosphate buffer to dissolve and adjust the pH to 8.5, add 25U / mL α-amino acid ester acyltransferase and stir at 25℃ for 3h, then heat to 50℃ to inactivate the enzyme for 20min, cool and purify, and freeze dry to obtain leucine-glycine dipeptide; Step 2. Disperse 50g of potato PRS3 starch into 200mL of water to prepare a starch milk with a mass fraction of 20%. Add 1.5g of chitosan oligosaccharide and 0.25g of zinc gluconate to the starch milk and stir for 1h at 50℃ and 200rpm. Then add 50mL of leucine-glycine dipeptide solution with a mass concentration of 5% and continue treatment for 2h. Vacuum dry at 55℃ to obtain composite modified potato PRS3 starch. Example 2

[0019] A method for preparing composite modified potato PRS3 starch includes the following steps: Step 1. Mix 14.7g leucine methyl ester hydrochloride and 7.5g glycine, add 200mL 0.1mol / L phosphate buffer to dissolve and adjust pH to 8.0, add 60U / mL α-amino acid ester acyltransferase and stir at 28℃ for 2h, then heat to 55℃ to inactivate enzyme for 25min, cool and purify, freeze dry to obtain leucine-glycine dipeptide; Step 2. Disperse 75g of potato PRS3 starch into 300mL of water to prepare a starch milk with a mass fraction of 20%. Add 3g of chitosan oligosaccharide and 0.375g of zinc gluconate to the starch milk and stir for 1h at 55℃ and 200rpm. Then add 75mL of 4% leucine-glycine dipeptide solution and continue treatment for 1.5h. Vacuum dry at 55℃ to obtain composite modified potato PRS3 starch. Example 3

[0020] A method for preparing composite modified potato PRS3 starch includes the following steps: Step 1. Mix 22.05g of leucine methyl ester hydrochloride and 12.9g of glycine, add 300mL of 0.1mol / L phosphate buffer to dissolve and adjust the pH to 9.0, add 40U / mL of α-amino acid ester acyltransferase and stir at 30℃ for 1h, then heat to 50℃ to inactivate the enzyme for 20min, cool and purify, and freeze-dry to obtain leucine-glycine dipeptide; Step 2. Disperse 50g of potato PRS3 starch into 200mL of water to prepare a starch milk with a mass fraction of 20%. Add 4g of chitosan oligosaccharide and 0.5g of zinc gluconate to the starch milk and stir for 2h at 60℃ and 300rpm. Then add 50mL of 8% leucine-glycine dipeptide solution and continue treatment for 1h. Vacuum dry at 50℃ to obtain composite modified potato PRS3 starch. Example 4

[0021] A method for preparing composite modified potato PRS3 starch includes the following steps: Step 1. Mix 11.05 g leucine methyl ester hydrochloride and 5.65 g glycine, add 150 mL 0.1 mol / L phosphate buffer to dissolve and adjust the pH to 8.5, add 45 U / mL α-amino acid ester acyltransferase and stir at 27 °C for 2.5 h, then heat to 50 °C to inactivate the enzyme for 20 min, cool and purify, and freeze-dry to obtain leucine-glycine dipeptide; Step 2. Disperse 60g of potato PRS3 starch into 340mL of water to prepare a starch milk with a mass fraction of 15%. Add 3g of chitosan oligosaccharide and 0.3g of zinc gluconate to the starch milk and stir for 1h at 52℃ and 220rpm. Then add 70mL of 6% leucine-glycine dipeptide solution and continue treatment for 2h. Vacuum dry at 55℃ to obtain composite modified potato PRS3 starch. Example 5

[0022] A method for preparing composite modified potato PRS3 starch includes the following steps: Step 1. Mix 18.4 g leucine methyl ester hydrochloride and 9.4 g glycine, add 250 mL 0.1 mol / L phosphate buffer to dissolve and adjust the pH to 8.8, add 55 U / mL α-amino acid ester acyltransferase and stir at 30 °C for 2 h, then heat to 50 °C to inactivate the enzyme for 20 min, cool and purify, and freeze dry to obtain leucine-glycine dipeptide; Step 2. Disperse 90g of potato PRS3 starch into 210mL of water to prepare a starch milk with a mass fraction of 30%. Add 4.5g of chitosan oligosaccharide and 0.9g of zinc gluconate to the starch milk and stir for 1.5h at 60℃ and 200rpm. Then add 70mL of 3% leucine-glycine dipeptide solution and continue treatment for 2h. Vacuum dry at 50℃ to obtain composite modified potato PRS3 starch. Comparative Example 1

[0023] The difference between this comparative example and Example 3 is that chitosan oligosaccharide and zinc salt are not added; the remaining operations are the same as in Example 3. Comparative Example 2

[0024] The difference between this comparative example and Example 3 is that leucine-glycine dipeptide is not added; the remaining operations are the same as in Example 3. Comparative Example 3

[0025] The difference between this comparative example and Example 3 is that no zinc salt is added; the remaining operations are the same as in Example 3. Performance testing

[0026] (1) Freeze-thaw water separation rate Weigh 20 mL of 1.5% (w / w) PRS3 suspension into an empty weight tube. Heat to 95℃ and hold for 5 min, cool to room temperature, and freeze at -20℃ for 24 h. After removing from the freezer, thaw in a 30℃ water bath for 5 h. After 5 cycles, centrifuge at 4000 r / min for 20 min, discard the supernatant, and weigh. The formula for calculating the freeze-thaw water separation rate is as follows:

[0027] In the formula, m0 represents the mass of the centrifuge tube, m1 represents the mass of the starch suspension and the centrifuge tube, and m2 represents the mass after the supernatant is poured out.

[0028] (2) Solubility and swelling power Weigh 20 mL of 1.5% (w / w) PRS3 suspension into an empty tube. Record the dry weight of starch as m1. Heat to 95℃ and maintain for 10 min. After cooling to room temperature, centrifuge at 4000 r / min for 20 min. Decant the supernatant and record the weights of the precipitate, centrifuge tube, and supernatant after drying. The formulas for calculating solubility and swelling power are as follows:

[0029]

[0030] In the formula: m0 represents the mass of the centrifuge tube, m1 represents the mass of the dry starch, m2 represents the mass of the remaining precipitate and the centrifuge tube, and m3 represents the mass of the supernatant after drying.

[0031] (3) Transparency Prepare a 1.5% PRS3 suspension, place it in a 95℃ water bath, stir for 30 min, cool to room temperature, and measure the transmittance at 620 nm with distilled water as a blank control.

[0032] (4) Oil absorption Weigh 1g of PRS3 and 6mL of soybean oil into a centrifuge tube and mix continuously with stirring. Vortex the tube for 5 minutes, let it stand for 30 minutes to absorb the oil, and then centrifuge at 3000 rpm for 20 minutes. Discard the supernatant, dry the precipitate, and weigh it. The increase in weight is expressed as the oil absorption capacity. The formula for calculating oil absorption capacity is as follows:

[0033] In the formula: m1 represents the mass of PRS3, and m2 represents the mass of the precipitate after drying.

[0034] (5) Milk absorbability Add 0.1g PRS3 to 2mL of raw milk and proceed as described in (4). After drying, weigh the precipitate. The formula for milk absorbability is:

[0035] In the formula: m1 represents the mass of PRS3, and m2 represents the mass of the precipitate after drying.

[0036] (6) Water retention Add 0.45g PRS3 and 15mL distilled water to a pre-weighed 50mL centrifuge tube, place in a 37℃ water bath for 1 hour, centrifuge at 10000r / min for 10 minutes, discard the supernatant, weigh the centrifuge tube, and the formula for calculating the water holding capacity is as follows:

[0037] In the formula: m0 represents the mass of the centrifuge tube, m1 represents the mass of PRS3 and distilled water, and m2 represents the mass after discarding the supernatant.

[0038] Table 1. Physicochemical properties of Examples 1-5, Comparative Examples 1-3, and native potato starch.

[0039] As shown in Table 1, the freeze-thaw water separation rate of Examples 1-5 was significantly lower than that of Comparative Examples 1-3, and the solubility, transparency, and milk absorption were all higher than those of Comparative Examples 1-3. The water-holding capacity was significantly higher than that of unmodified potato PRS3 starch. This indicates that the Zn content in the composite modified potato PRS3 starch described in this invention is significantly higher than that in Comparative Examples 1-3. 2+ It forms a reversible three-dimensional coordination network with chitosan oligosaccharide and starch molecular chains, effectively inhibiting starch aggregation and improving transparency. At the same time, it enhances freeze-thaw stability through the reversible contraction-recovery properties of coordination bonds. Meanwhile, the hydrophobic end of the leucine-glycine dipeptide inserts into the starch double helix structure, disturbing the crystallization region and reducing the tendency for retrogradation. The hydrophilic end interacts with the coordination network, enhancing hydration capacity and promoting the formation of regular crystal forms. Example 6

[0040] A method for preparing modified potato resistant starch-based yogurt includes the following steps: S1. Weigh 20g of the composite modified potato PRS3 starch prepared in Example 3 and mix it with 200mL of water. Stir at 70℃ for 15min to pregelatinize the starch to obtain pregelatinized starch. Then, preheat 400mL of milk to 42℃. Add the pregelatinized starch solution to the preheated milk and add a sweetener consisting of 2.0g xylitol, 0.032g acesulfame potassium and 0.004g neotame. Stir and mix well to obtain a mixture. S2. After preheating the mixture to 82°C, homogenize it for 12 minutes under a homogenization pressure of 20 MPa. Then, heat it to 90°C at the center of the mixture and pasteurize it for 8 minutes. After sterilization, cool it to 38°C and inoculate it with 24 mL of activated starter culture (composed of 4.8 mL of Lactobacillus bulgaricus culture, 4.8 mL of Streptococcus thermophilus culture, 4.8 mL of Lactobacillus paracasei culture, 4.8 mL of Lactobacillus acidophilus culture, and 4.8 mL of Bifidobacterium animalis culture). Stir well and then dispense the mixture. S3. Ferment the packaged liquid at 40℃ for 11 hours, cool it rapidly to 6℃, and then ripen it at 4℃ for 24 hours. Finally, store it at 4℃ to obtain modified potato resistant starch set yogurt. Example 7

[0041] A method for preparing modified potato resistant starch-based yogurt includes the following steps: S1. Weigh 24g of the composite modified potato PRS3 starch prepared in Example 3 and mix it with 200mL of water. Stir at 75℃ for 15min to pregelatinize the starch to obtain pregelatinized starch. Then, preheat 400mL of milk to 40℃. Add the pregelatinized starch solution to the preheated milk and add a sweetener consisting of 2.4g xylitol, 0.04g acesulfame potassium and 0.0032g neotame. Stir and mix well to obtain a mixture. S2. After preheating the mixture to 80°C, homogenize it for 10 minutes under a homogenization pressure of 20 MPa. Then, heat it to 95°C at the center of the mixture and pasteurize it for 10 minutes. After sterilization, cool it to 40°C and inoculate it with 24 mL of activated starter culture (composed of 4 mL of Lactobacillus bulgaricus culture, 4 mL of Streptococcus thermophilus culture, 8 mL of Lactobacillus paracasei culture, 4 mL of Lactobacillus acidophilus culture, and 4 mL of Bifidobacterium animalis culture). Stir it evenly and then dispense the mixture. S3. Ferment the packaged liquid at 42℃ for 10 hours, quickly cool it to 6℃, and then ripen it at 4℃ for 24 hours. Finally, store it at 4℃ to obtain modified potato resistant starch set yogurt. Example 8

[0042] A method for preparing modified potato resistant starch-based yogurt includes the following steps: S1. Weigh 16g of the composite modified potato PRS3 starch prepared in Example 3 and mix it with 200mL of water. Stir at 70℃ for 15min to pregelatinize the starch to obtain pregelatinized starch. Then, preheat 400mL of milk to 42℃. Add the pregelatinized starch solution to the preheated milk and add a sweetener consisting of 1.6g xylitol, 0.024g acesulfame potassium and 0.0048g neotame. Stir and mix well to obtain a mixture. S2. After preheating the mixture to 85°C, homogenize it for 10 minutes under a homogenization pressure of 20 MPa. Then, heat it to 90°C at the center of the mixture and pasteurize it for 10 minutes. After sterilization, cool it to 40°C and inoculate it with 24 mL of activated starter culture (composed of 4.8 mL of Lactobacillus bulgaricus culture, 4.8 mL of Streptococcus thermophilus culture, 4.8 mL of Lactobacillus paracasei culture, 4.8 mL of Lactobacillus acidophilus culture, and 4.8 mL of Bifidobacterium animalis culture). Stir well and then dispense the mixture. S3. Ferment the packaged liquid at 40℃ for 9 hours, quickly cool it to 6℃, and then ripen it at 4℃ for 24 hours. Finally, store it at 4℃ to obtain modified potato resistant starch set yogurt. Example 9

[0043] A method for preparing modified potato resistant starch-based yogurt includes the following steps: S1. Weigh 24g of the composite modified potato PRS3 starch prepared in Example 3 and mix it with 200mL of water. Stir at 70℃ for 15min to pregelatinize the starch to obtain pregelatinized starch. Then, preheat 400mL of milk to 42℃. Add the pregelatinized starch solution to the preheated milk and add a sweetener consisting of 1.6g xylitol, 0.036g acesulfame potassium and 0.004g neotame. Stir and mix well to obtain a mixture. S2. After preheating the mixture to 80℃, homogenize it for 10 minutes under a homogenization pressure of 20MPa. Then, heat it to 95℃ at the center of the mixture and pasteurize it for 10 minutes. After sterilization, cool it to 40℃ and inoculate it with 28mL of activated starter culture (composed of 5.6mL Lactobacillus bulgaricus culture, 5.6mL Streptococcus thermophilus culture, 11.2mL Lactobacillus paracasei culture, 5.6mL Lactobacillus acidophilus culture, and 5.6mL Bifidobacterium animalis culture). Stir well and then dispense the mixture. S3. Ferment the packaged liquid at 40℃ for 9 hours, quickly cool it to 6℃, and then ripen it at 4℃ for 24 hours. Finally, store it at 4℃ to obtain modified potato resistant starch set yogurt. Example 10

[0044] A method for preparing modified potato resistant starch-based yogurt includes the following steps: S1. Weigh 12g of the composite modified potato PRS3 starch prepared in Example 3 and mix it with 200mL of water. Stir at 70℃ for 15min to pregelatinize the starch to obtain pregelatinized starch. Then, preheat 400mL of milk to 42℃. Add the pregelatinized starch solution to the preheated milk and add a sweetener consisting of 2.4g xylitol, 0.024g acesulfame potassium and 0.004g neotame. Stir and mix well to obtain a mixture. S2. After preheating the mixture to 85°C, homogenize it for 15 minutes under a homogenization pressure of 25 MPa. Then, heat it to 95°C at the center of the mixture and pasteurize it for 10 minutes. After sterilization, cool it to 40°C and inoculate it with 28 mL of activated starter culture (composed of 4 mL of Lactobacillus bulgaricus culture, 4 mL of Streptococcus thermophilus culture, 12 mL of Lactobacillus paracasei culture, 4 mL of Lactobacillus acidophilus culture, and 4 mL of Bifidobacterium animalis culture). Stir it evenly and then dispense the mixture. S3. Ferment the packaged liquid at 42℃ for 10 hours, quickly cool it to 6℃, and then ripen it at 4℃ for 24 hours. Finally, store it at 4℃ to obtain modified potato resistant starch set yogurt. Comparative Example 4

[0045] The difference between this comparative example and Example 7 is that it uses the composite modified potato PRS3 starch prepared in Comparative Example 1. The remaining operations are the same as in Example 7. Comparative Example 5

[0046] The difference between this comparative example and Example 7 is that the composite modified potato PRS3 starch prepared in Comparative Example 2 was used. The remaining operations are the same as in Example 7. Comparative Example 6

[0047] The difference between this comparative example and Example 7 is that it uses the composite modified potato PRS3 starch prepared in Comparative Example 3. The remaining operations are the same as in Example 7. Comparative Example 7

[0048] The difference between this comparative example and Example 7 is that unmodified potato PRS3 starch was used; the remaining operations are the same as in Example 7. Performance testing

[0049] (1) Sensory evaluation The sensory evaluation method for PRS3 set-type yogurt was based on GB19302-2010 "National Food Safety Standard for Fermented Milk". It was completed by a sensory evaluation team of 10 food professionals (5 men and 5 women). The members of the sensory evaluation team scored all yogurt samples according to the sensory scoring table 2. The scoring content included texture (weight 0.33), mouthfeel (weight 0.25), flavor (weight 0.21), and color (weight 0.21).

[0050] Table 2 Sensory evaluation criteria for modified potato resistant starch set-type yogurt

[0051] Table 3 Sensory evaluation scores of Examples 6-10 and Comparative Examples 4-7

[0052] As shown in Table 3, the sensory scores of the modified potato resistant starch set-type yogurt prepared in Examples 6-10 were better than those of Comparative Examples 4-7. This indicates that the composite modified potato PRS3 starch has excellent milk absorption characteristics. Its three-dimensional coordination network enables casein to be efficiently adsorbed onto the starch surface, forming a uniform and dense gel network with no whey separation and a milky white and bright color. At the same time, the leucine-glycine dipeptide can further improve the absorption and stability of milk proteins in milk, thus giving the modified potato resistant starch set-type yogurt good sensory quality.

[0053] (2) Yogurt storage quality evaluation test During storage, the samples were kept in a refrigerator at 4°C. Samples were taken out on days 1, 3, 6, 9, 15, 21, and 27 for the determination of the following indicators. The specific determination methods are as follows: ① Acidity: Weigh 10g of yogurt sample into an Erlenmeyer flask, add 20mL of boiled and cooled distilled water to room temperature, and 2 drops of 0.5% phenolphthalein indicator. Mix well and titrate with 0.1mol / L NaOH standard solution until a faint pink color appears and does not fade within 30s. Record the volume of NaOH standard solution consumed. The acidity value of yogurt is expressed in °T, and its calculation formula is as follows:

[0054] In the formula, X represents the acidity of the yogurt, C represents the concentration of the NaOH standard solution, V represents the volume of NaOH standard solution consumed during titration, and m represents the mass of the yogurt.

[0055] ②Gel strength: A P / 0.5 probe was selected, and compression mode was used. The speed was set to 1.5 mm / s before the test, 1 mm / s during the test, and 10 mm / s after the test, with a compression distance of 20 mm. The gel strength of the yogurt was then measured. ③Textural properties: The hardness, elasticity, cohesiveness and adhesiveness of yogurt were analyzed using an A / BE-35 probe. The measurement conditions were: measurement speed of 1 mm / s, pre-measurement speed of 2 mm / s, post-measurement speed of 2 mm / s, forward distance of 20 mm, and sensing force of 5 g.

[0056] ④ Total number of viable lactic acid bacteria and number of bifidobacteria: The number of viable lactic acid bacteria shall be determined according to GB4789.35-2016 National Food Safety Standard, Microbiological Examination of Food, Lactic Acid The bacteria were tested according to the "Bacterial Test".

[0057] ⑤ Water-holding capacity: Accurately weigh 10g (accurate to 0.01g) of sample into a 50mL centrifuge tube, centrifuge at 3000r / min for 20min, discard the supernatant, and accurately weigh the remaining precipitate. The formula for calculating the water-holding capacity is as follows:

[0058] In the formula: m0 represents the mass of the centrifuge tube, m1 represents the mass of the yogurt sample, and m2 represents the mass of the remaining precipitate and the centrifuge tube.

[0059] Depend on Figure 1 , Figure 2 and Figure 3 It can be seen that the modified potato resistant starch set-type yogurt prepared in Example 7 has better acidity, water-holding capacity, lactic acid bacteria survival, and textural properties than Comparative Examples 4-7 and commercially available yogurts during storage. This is due to the presence of chitosan oligosaccharide-Zn. 2+ The leucine-glycine dipeptide composite modified starch can efficiently adsorb milk proteins through its porous structure and abundant surface active sites, promoting the formation of a dense casein-whey protein cross-linked gel network in yogurt. This effectively delays the rise in acidity during storage, maintains good water-holding capacity, and prevents whey separation and textural deterioration. Simultaneously, the composite carrier provides excellent protection for probiotics, ensuring that lactic acid bacteria and bifidobacteria maintain high activity during storage, significantly superior to ordinary commercially available yogurt. Furthermore, the modified potato resistant starch-based settling yogurt in Example 7 exhibits stronger cohesiveness and viscosity, with the strongest internal gel network binding force, effectively resisting physical stress during storage. In contrast, commercially available yogurt, lacking the support of the composite modified starch, shows a significant decrease in hardness, consistency, and gel strength, and is prone to whey separation.

[0060] (3) Short-chain fatty acid content ① In vitro fermentation model i. Preparation of in vitro simulated digestive fluid: Sample digestive fluid was prepared by simulating human oral, gastric and intestinal digestion in vitro. Using the set-type yogurt prepared in Example 7 and Comparative Examples 4-7, as well as ordinary yogurt, as the test objects, 60g / L LRS3 set-type yogurt solutions (referred to as Example 7, Comparative Example 4, Comparative Example 5, and Comparative Example 6, respectively) and 60g / L ordinary yogurt solutions were prepared. 10mL of each solution was added to 1mL of 1200U / mL α-amylase. After incubation in a water bath at 37℃, 120r / min, and in the dark for 15min, the pH of the system was adjusted to 3 with HCl solution. 1.6mL of 24000U / mL pepsin was added, and the solution was incubated in a water bath at 37℃, 120r / min, and in the dark for 3h. Then, the pH was adjusted to 7 with NaOH, and 2mL of 1000U / mL trypsin and 1mL of 4% porcine bile salts were added. The solution was incubated in a water bath at 37℃, 120r / min, and in the dark for 3h to obtain the in vitro digestion simulation solution. ii. Preparation of fecal microbial suspension Fresh feces were collected from 6 healthy volunteers (3 males and 3 females) with no history of gastrointestinal disease and no use of antibiotics within the past six months. The feces were mixed with phosphate buffer (pH 7.2) at a ratio of 1:10 (W / V) under anaerobic conditions. Then, the impurities in the feces were removed with sterile gauze and placed in a beaker. The supernatant was collected to obtain a fecal bacterial suspension. iii Simulated fermentation Add 27 mL of anaerobic culture medium (2 g each of peptone, yeast extract and sodium bicarbonate, 0.04 g each of potassium dihydrogen phosphate and dipotassium hydrogen phosphate, 0.2 g of sodium chloride, 0.01 g each of CaCl2•6H2O and Mg2SO4•7H2O, 2 mL of Tween 80, 50 mg of heme chloride, 10 μg of vitamin K1, 0.5 g of L-cysteine, and 1 L of water) to the Erlenmeyer flasks, 3 mL of fecal suspension, and 1 mL of samples after different in vitro simulated digestion. The blank group (BCG group) used an equal volume of distilled water instead of samples. After thorough mixing, anaerobic culture was carried out at 37 °C for 24 h. ② Determination of short-chain fatty acid content i Sample pretreatment After 24 hours of fermentation, the sample was transferred to a centrifuge tube and centrifuged at 12000 rpm and 4℃ for 5 min. 5 mL of the supernatant was taken into the centrifuge tube, and 0.5 mL of 50% sulfuric acid solution and 5 mL of diethyl ether were added. The mixture was vortexed for 1 min and then centrifuged at 10000 rpm for 5 min at 4℃. The upper diethyl ether layer was taken, filtered through a 0.22 μm organic phase filter membrane, and stored in a gas chromatography vial for analysis.

[0061] ii. Gas chromatographic conditions Machine model: Agilent GC-7890A; Injector: Injector temperature 220℃, split ratio 10:1, nitrogen constant flow, column flow rate 1.5mL / min; Chromatographic column: 10mDB-WAX capillary column; initial temperature 70℃, hold for 1 min, increase to 160℃ at 15℃ / min, hold for 6 min, increase to 210℃ at 30℃ / min, hold for 5 min; Detector: Detector temperature 250℃, flame hydrogen detector (FID).

[0062] Table 4 Short-chain fatty acids of Example 7, Comparative Examples 4-7 and regular yogurt

[0063] As shown in Table 4, the modified potato resistant starch set-type yogurt prepared in Example 7 can significantly promote the secretion of acetic acid, propionic acid and isovaleric acid. This indicates that the composite modified potato PRS3 starch can be utilized by the intestinal microorganisms, promoting the formation of short-chain fatty acids by the intestinal microorganisms. At the same time, chitosan oligosaccharide and leucine-glycine dipeptide can also act as prebiotics to promote the probiotic effect of intestinal probiotics, enabling the intestinal flora to produce beneficial short-chain fatty acids, thereby effectively regulating the intestinal health of the body.

[0064] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. Any person skilled in the art can make many possible variations and modifications to the technical solutions of the present invention, or modify them into equivalent embodiments, without departing from the spirit and technical essence of the present invention. Therefore, any simple modifications, equivalent substitutions, equivalent changes, and modifications made to the above embodiments based on the technical essence of the present invention, without departing from the content of the technical solutions of the present invention, shall still fall within the scope of protection of the present invention.

Claims

1. A method for preparing modified potato resistant starch, characterized in that, Includes the following steps: S1. Add chitosan oligosaccharide and zinc salt to potato PRS3 starch milk and mix. S2. The mixture is then reacted with a leucine-glycine dipeptide solution and dried to obtain composite modified potato PRS3 starch.

2. The method for preparing modified potato resistant starch according to claim 1, characterized in that: The mass fraction of potato PRS3 starch milk in S1 is 15-30%, the amount of chitosan oligosaccharide added is 1-8%, and the amount of zinc salt added is 0.1-1%, based on the mass of potato PRS3 starch.

3. The method for preparing modified potato resistant starch according to claim 1, characterized in that: The mass concentration of the leucine-glycine dipeptide solution in S2 is 2-10%, and the volume ratio of the leucine-glycine dipeptide solution to potato PRS3 starch milk is 1:(2-5).

4. The method for preparing modified potato resistant starch according to claim 3, characterized in that: The leucine-glycine dipeptide is prepared by mixing and dissolving leucine methyl ester and glycine in a molar ratio of 1:(0.6-1.5), adding α-amino acid ester acyltransferase and treating for 1-3 hours at 25-35℃ and pH 8.0-9.0, followed by enzyme inactivation and purification.

5. Composite modified potato PRS3 starch prepared by the method according to any one of claims 1-4.

6. The application of the composite modified potato PRS3 starch according to claim 5 in the preparation of set-type yogurt.

7. The application according to claim 6, characterized in that, The preparation method of the set-type yogurt is as follows: the compound modified potato PRS3 starch is pregelatinized and mixed with milk. After adding auxiliary materials, it is homogenized and sterilized, inoculated and fermented, and then matured to produce potato resistant starch set-type yogurt.

8. The application according to claim 7, characterized in that: The amount of the composite modified potato PRS3 starch added is 3-6%; the auxiliary materials consist of 0.4-0.6% xylitol, 0.006-0.01% acesulfame potassium and 0.0008-0.0012% neotame.

9. The application according to claim 7, characterized in that: The homogenization sterilization conditions are: homogenization pressure 15-25 MPa, homogenization time 10-15 min, sterilization temperature 85-95℃, and sterilization time 5-10 min.

10. The application according to claim 7, characterized in that: The inoculation and fermentation conditions are as follows: inoculum amount of starter culture 5-8%, fermentation temperature 38-44℃, fermentation time 8-11h; the starter culture is composed of Lactobacillus bulgaricus, Streptococcus thermophilus, Lactobacillus paracasei, Lactobacillus acidophilus, and Bifidobacterium animalis in a ratio of 1:1:(1-3):1:1; the post-ripening conditions are as follows: treatment temperature 2-6℃, post-ripening time 20-25h.

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