A fermented soy food and a method for preparing the same

Abstract

The present application relates to a kind of preparation methods of legume fermented food, comprising the following steps: (1) providing first soybean milk, access first fermentation bacteria, anaerobic fermentation, fermentation end point is pH 4-5, obtain first fermentation product;The first fermentation bacteria are selected from one or more lactic acid bacteria;(2) providing second soybean milk, access second fermentation bacteria, anaerobic fermentation, fermentation length is 6-10h, obtain second fermentation product;The second fermentation bacteria are selected from one or more of Leuconostoc mesenteroides, Kluyveromyces marxianus and Saccharomyces cerevisiae;(3) according to 0.5-1.5:1 Weight ratio mixes first fermentation product with second fermentation product, aerobic fermentation is carried out to mixture, fermentation end point is to pH 4-6, obtain third fermentation product.

Description

Technical Field

[0001] This invention relates to the food industry, specifically to a fermented soybean food and its preparation method. Background Technology

[0002] Soy products are a popular traditional food in Asian countries. Soy milk is rich in protein, iron, unsaturated fatty acids, and niacin, while being low in fat, carbohydrates, and calcium. Consuming soy products offers direct and indirect health and nutritional benefits, such as providing high-quality plant protein, which helps lower serum cholesterol and prevent cardiovascular disease, cancer, and other chronic diseases.

[0003] Fermentation with lactic acid bacteria can increase the content of isoflavones and B vitamins in soy milk, enhancing its nutritional function. However, fermented soy yogurt retains the beany and rancid smell of soy milk, lacks the aroma of yogurt, and develops a strong sour and rancid odor after sterilization, reducing consumer acceptance of soy products. The main component of soy milk odor is hexanal, while other volatile compounds such as trans-2-hexenal, 1-octen-3-ol, n-hexanol, pentanol, benzaldehyde, and trans-, trans-2,4-decadienal also negatively impact soy milk flavor. These odor compounds are mainly produced through the lipoxygenase pathway. During soybean processing, the lipoxygenase-catalase pathway is rapidly activated due to moisture, oxygen, and temperature conditions, converting linoleic acid into hexanal and linolenic acid into cis-3-hexenal and other flavor compounds. The odor interacts with soy protein and is retained in soy products. While the hexanal content in fermented soy yogurt is significantly reduced, it is still perceptible to consumers due to its extremely low threshold. The content of 1-octen-3-ol, n-hexanol, and 2-pentylfuran in soy yogurt is higher than that in milk yogurt. These flavor compounds contribute to the beany and sour taste of soy yogurt. There is limited research on the sour taste of pasteurized soy yogurt, but it is speculated that it is due to the combination of diacetyl with other flavor compounds in soy yogurt after pasteurization, resulting in an off-flavor.

[0004] Currently, commercially available soy yogurts still have noticeable beany and rancid odors, and their overall flavor is less pleasant than that of milk yogurt. As shelf life extends, these unpleasant flavors worsen, making all products unacceptable to tasters towards the end of their shelf life. Cold-chain soy yogurts have a shorter shelf life and stricter storage requirements, hindering widespread adoption. Room-temperature soy yogurts offer fewer choices, tend to have higher viscosity, a greasy and unpleasant texture, and tend to stick to the sides of the container, failing to maintain stability during storage and exhibiting separation and water separation. Furthermore, many stabilizers are added to the ingredient list, failing to meet consumers' expectations for clean ingredient lists. Summary of the Invention

[0005] This invention utilizes a multi-stage fermentation process to produce bean-based yogurt (e.g., soy yogurt) with a refreshing taste and no beany or beany odor.

[0006] In a first aspect, this application provides a method for preparing fermented soybean food, comprising the following steps:

[0007] Provide the first batch of soy milk, inoculate it with the first fermentation bacteria, and carry out anaerobic fermentation. The fermentation endpoint is pH 4-5 (e.g., 4.6-4.8), to obtain the first fermentation product.

[0008] The first fermentation bacteria are selected from one or more lactic acid bacteria;

[0009] (2) Provide the second soy milk, inoculate it with the second fermentation bacteria, and ferment it anaerobically for 4 to 10 hours to obtain the second fermentation product;

[0010] The second fermentation strain is selected from one or more of Leuconostoc mesenteroides, Kluyveromyces martensii, and Saccharomyces cerevisiae;

[0011] (3) Mix the first fermentation product and the second fermentation product in a weight ratio of 0.5-1.5:1 (e.g., 0.8-1.2:1), and carry out aerobic fermentation on the mixture until the pH reaches 4.2-4.4 to obtain the third fermentation product.

[0012] In the above scheme, the purpose of the first fermentation is to obtain conventionally fermented soybean yogurt; the purpose of the second fermentation is to obtain a special fermentation bacteria culture with high bacterial count and high enzyme activity. After the first and second fermentations are completed, the two yogurts are thoroughly mixed, and the anaerobic environment is removed to allow for aerobic fermentation. The aerobic environment not only reduces or eliminates the production of alcohol by the second fermentation bacteria, but also enables the abundant aldehyde dehydrogenase and ketone dehydrogenase in the second fermentation bacteria to convert unpleasant flavor substances in the yogurt into pleasant esters, giving the yogurt a unique fruity flavor without any beany or musty odor, making it more appealing.

[0013] In some implementations, in step (1), the protein concentration of the first soy milk is 2%-4%, for example, 3%.

[0014] In some implementations, in step (1), the inoculum amount of the first fermentation bacteria is 0.1 U / L-0.2 U / L.

[0015] In some implementations, the fermentation temperature in step (1) is 37-42°C.

[0016] In some implementations, the fermentation time in step (1) is 6 to 10 hours (e.g., 8 hours).

[0017] In some implementations, in step (1), lactic acid bacteria (LAB) is a general term for a class of bacteria (e.g., non-spore-forming, Gram-positive bacteria) that degrade fermentable carbohydrates to produce lactic acid.

[0018] In some embodiments, the lactic acid bacteria are selected from one or more of Streptococcus thermophilus, Lactobacillus bulgaricus, Lactobacillus acidophilus, Lactobacillus plantarum, Lactobacillus casei, Lactococcus lactis, and Bifidobacterium.

[0019] In some implementations, in step (1), the lactococcus is selected from one or more of the lactococcus lactis subsp. lactis and lactococcus lactis subsp. lactis.

[0020] In some implementations, in step (1), the Bifidobacterium is selected from one or more of Bifidobacterium adolescentis, Bifidobacterium animalis subsp. animalis, Bifidobacterium animalis subsp. lactis, Bifidobacterium bifidum, Bifidobacterium breve, Bifidobacterium infantis, and Bifidobacterium longum.

[0021] In some embodiments, the first fermentation bacteria include Lactobacillus bulgaricus and Streptococcus thermophilus, with a live count ratio of 1:0.1 to 10, for example 1:1 to 10, or 1:1 to 3.

[0022] In some implementations, in step (2), the protein concentration of the second soy milk is 2%-4%.

[0023] In some implementations, in step (2), the second fermenting bacteria is a yeast, such as Kluyveromyces MAX.

[0024] In some implementations, in step (2), the inoculation amount of the second fermentation bacteria is 0.002 U / L-0.02 U / L (e.g., 0.01 U / L-0.02 U / L).

[0025] In some implementations, the fermentation temperature in step (2) is 28-37°C, for example 25-28°C.

[0026] In some implementations, the fermentation time in step (2) is 4 to 10 hours, for example, 8 hours.

[0027] In some implementations, in step (2), the Leuconostoc mesenteroides is the Leuconostoc mesenteroides subsp. mesenteroides.

[0028] In some implementations, the fermentation temperature in step (3) is 25-43°C, for example 35-40°C.

[0029] In some implementations, the fermentation time in step (3) is 2 to 4 hours, for example, 3 hours.

[0030] In some implementation methods, the preparation method of fermented soybean products further includes the steps of preparing a first soy milk and a second soy milk, specifically including:

[0031] (a1) Perform enzyme-inactivating heat treatment on soybeans;

[0032] (a2) Grind and filter the enzyme-inactivated soybeans to obtain soybean milk base;

[0033] (a3) Pre-treat the soybean milk base material before fermentation to obtain the first soybean milk and the second soybean milk.

[0034] In some implementations, in step (a1), the enzyme-inactivating heat treatment is a dry heat treatment.

[0035] In some implementations, in step (a1), the temperature of the enzyme-inactivating heat treatment is 180°C to 240°C.

[0036] In some implementations, in step (a1), the enzyme-inactivating heat treatment time is 2 to 8 minutes.

[0037] In some implementations, in step (a1), the beans are whole, unpeeled beans.

[0038] In some implementations, in step (a1), the grains are soybeans.

[0039] In some implementations, in step (a2), the pulp has one or more of the following characteristics:

[0040] The temperature of the water used for grinding is 80–95℃;

[0041] The dissolved oxygen in the grinding water is below 3 ppm;

[0042] The soybean-to-water weight ratio during grinding is 1:6 to 1:8.

[0043] The grinding time for the pulp is 15-30 minutes;

[0044] Before grinding, the soybeans are peeled.

[0045] In some implementations, step (a3) ​​includes one or more of the following operations:

[0046] (b1) Protein concentration regulation;

[0047] (b2) Add flavoring agents, conditioning agents and stabilizers;

[0048] (b3) Shearing and mixing;

[0049] (b4) pH adjustment;

[0050] (b5) Homogeneous;

[0051] (b6) Sterilization.

[0052] In some embodiments, the pre-fermentation pretreatment has one or more of the following characteristics:

[0053] In operation (b1), the protein concentration is adjusted to 2%-4%;

[0054] In operation (b3), the shearing and mixing time is 10-15 min;

[0055] In operation (b4), adjust the pH to 6.5-7.0;

[0056] In operation (b5), homogenization refers to homogenization at 60-70°C using a pressure of 25-35 MPa;

[0057] In operation (b6), sterilization refers to sterilization at 95°C for 5-15 minutes.

[0058] In some implementation schemes, it also includes:

[0059] (4) Post-fermentation treatment of the third fermentation product;

[0060] The post-fermentation treatment includes one or more of the following operations:

[0061] (c1) Protein concentration regulation;

[0062] (c2) Add formulation excipients, formulation excipients and stabilizers;

[0063] (c3) Shearing and mixing;

[0064] (c4) pH adjustment;

[0065] (c5) Homogeneous;

[0066] (c6) Sterilization.

[0067] In some embodiments, the post-fermentation treatment has one or more of the following features:

[0068] In operation (c1), the protein concentration is adjusted to 1%-3%;

[0069] In operation (c3), the shearing and mixing time is 10-15 min;

[0070] In operation (c4), adjust the pH to 4.2-4.4;

[0071] In operation (c5), homogenization refers to homogenization at 60-62°C using a pressure of 10-25 MPa;

[0072] In operation (c6), sterilization refers to sterilization at 75°C for 20-60 seconds.

[0073] In some implementation schemes, compounding excipients can refer to excipients that can be used to adjust the flavor of food, conditioning excipients can refer to excipients that can be used to adjust the texture of food, and stabilizers can refer to food additives that can be used to shape food and maintain its shape and texture stability.

[0074] In some implementation schemes, the additives are selected from one or more of sugar and fruit juice.

[0075] In some implementation schemes, the conditioning adjuvants are selected from one or more of starch, salt, fruit pulp, and dietary fiber.

[0076] In some implementations, the stabilizer is selected from one or more of pectin, carrageenan, gellan gum, agar, or soybean polysaccharides.

[0077] In some implementations, the fermented soybean product is soybean yogurt.

[0078] In some implementation schemes, depending on the processing method of the third fermentation product, the preparation of the third fermentation product can be called different types of yogurt products, such as live-culture yogurt or room-temperature yogurt.

[0079] In some implementations, the hexanal content of soy yogurt (e.g., live culture type) is less than 25 ng / ml (e.g., less than 20 ng / ml, e.g., less than 15 ng / ml) and the 1-octen-3-ol content is less than 2 ng / ml (e.g., less than 1.8 ng / ml) over a 35-day shelf life.

[0080] In some implementations, the hexanal content of soy yogurt (e.g., room temperature type) is less than 65 ng / ml (e.g., less than 60 ng / ml) and the 1-octen-3-ol content is less than 1.3 ng / ml (e.g., less than 1.2 ng / ml) over a 35-day shelf life.

[0081] In some embodiments, this application provides a method for preparing soy-based yogurt, comprising the following steps:

[0082] (1) Whole soybean enzyme inactivation: Place whole soybeans in an oven and heat them at 170-190℃ for 5-7 minutes. After the oven is finished, let them cool naturally and then use a soybean peeling machine to peel them.

[0083] (2) Grinding: Grind the peeled soybeans obtained in step (1) into a paste, control the soybean-to-water ratio to be 1:7-9, the grinding water temperature to be 85-95℃, the dissolved oxygen in the water to be 1-10ppm, grind for 20-40 minutes and then filter to obtain soybean milk base.

[0084] (3) Ingredients: Adjust the protein concentration of the soybean milk base to 2-4%, add the pre-set auxiliary materials, cut for 10-20 minutes and mix well, adjust the pH to 6-7, homogenize, sterilize and cool to obtain the fermentation base.

[0085] (4) Fermentation:

[0086] Using 50 parts by weight of fermentation base as the first soy milk, cool it to 35-40℃, add 0.1-0.3 U / L of the first fermentation bacteria, which include Lactobacillus bulgaricus and Streptococcus thermophilus (the ratio of the number of viable bacteria of the two is 2-4:6-8), anaerobic fermentation for 7-9 hours, reaching the fermentation endpoint pH 4-5, and obtaining the first fermentation product.

[0087] Use 50 parts by weight of the fermentation base as the second soy milk, and cool the other half of the fermentation base to 25-30℃, add the second fermentation bacteria, which is 0.01-0.02 U / L of Kluyveromyces martensii, and ferment anaerobicly for 6-10 hours to obtain the second fermentation product.

[0088] The first and second fermentation products are aseptically mixed, heated to 35-40°C, and fermented aerobically for 2-4 hours until the pH reaches below 4.4, which yields the third fermentation product.

[0089] (5) Post-fermentation treatment:

[0090] The third fermentation product is cooled and demulsified, and the pH is adjusted to 4-4.5 to obtain soy yogurt (live culture type).

[0091] In some embodiments, this application provides a method for preparing soy-based yogurt, comprising the following steps:

[0092] (1) Whole soybean enzyme inactivation: Place whole soybeans in an oven and heat them at 190-200℃ for 5-7 minutes. After the oven is finished, let them cool naturally and then use a soybean peeling machine to peel them.

[0093] (2) Grinding: Grind the peeled soybeans obtained in step (1) into a paste, control the soybean-to-water ratio to be 1:7-9, the grinding water temperature to be 85-95℃, the dissolved oxygen in the water to be 1-10ppm, grind for 20-40 minutes and then filter to obtain soybean milk base.

[0094] (3) Ingredients: Adjust the protein concentration of the soybean milk base to 3-5%, add the pre-set auxiliary materials, cut for 10-20 minutes and mix well, adjust the pH to 6-7, homogenize, sterilize and cool to obtain the fermentation base;

[0095] (4) Fermentation:

[0096] Using 50 parts by weight of fermentation base as the first soy milk, cool it to 38-42℃, add 0.1-0.3 U / L of the first fermentation bacteria, which include Lactobacillus bulgaricus and Streptococcus thermophilus (the ratio of the number of viable bacteria of the two is 2-4:6-8), anaerobic fermentation for 7-9 hours, reaching the fermentation endpoint pH 4-5, and obtaining the first fermentation product.

[0097] Using 50 parts by weight of fermentation base as the second soy milk, cooling it to 25-30℃, adding the second fermentation bacteria (using 0.01-0.02 U / L of Kluyveromyces martensii), and anaerobic fermentation for 4-6 hours, the second fermentation product is obtained.

[0098] The two fermentation products were aseptically mixed and heated to 35–40°C for aerobic fermentation for 2–4 hours until the final pH of 4–5 was reached. The mixture was then cooled to break the emulsion, yielding the third fermentation product.

[0099] (5) Post-fermentation treatment

[0100] Adjust the protein concentration of the third fermentation product obtained in step (4) to 2-4%, add the pre-set auxiliary materials, cut for 10-20 minutes and mix well, adjust the pH to 4-4.5, homogenize at room temperature, sterilize, cool and fill to obtain soy yogurt (room temperature drinking type).

[0101] In a second aspect, this application provides a fermented soybean food product prepared by the method described in any of the above-mentioned methods.

[0102] Terminology Explanation

[0103] The Chinese-Latin name correspondence of the strains used in this application is as follows.

[0104]

[0105]

[0106] Beneficial effects

[0107] The disclosed fermented soybean food and its preparation method have one or more of the following beneficial effects:

[0108] (1) This formula, through the specific combination of primary and secondary fermentation strains, reduces the content of undesirable flavor substances such as oxidized and sour taste in fermented soybean yogurt products. Under refrigeration, the unsterilized yogurt achieves a hexanal content of less than 13 ng / ml and a 1-octen-3-ol content of less than 1.5 ng / ml, meaning the yogurt has extremely low levels of undesirable flavors such as sourness and oxidation. After sterilization, the hexanal content is less than 24 ng / ml and the 1-octen-3-ol content is less than 1.3 ng / ml, meaning the yogurt retains its good flavor before sterilization, without any undesirable flavors such as sourness or oxidation, forming a clear distinction from the flavor of commercially available plant-based yogurt after sterilization.

[0109] (2) Some embodiments of this disclosure adopt a soybean heat treatment process, which, compared with the current industrial production direct grinding process, reduces the energy consumption of the grinding process, significantly reduces the content of undesirable flavors in soybean milk, and makes the content of the main undesirable flavor substance n-hexanal in soybean milk lower, making the overall flavor of soybean milk pleasant, without raw or beany smell, thereby weakening the undesirable flavors of subsequent fermentation.

[0110] (3) The soy yogurt disclosed herein has good shelf-life stability and can maintain good flavor during the shelf life without the need to add flavorings to the product. At the end of the shelf life, the content of undesirable flavor substances is lower than when the product was first produced. Detailed Implementation

[0111] The embodiments of the present invention will be described in detail below with reference to examples. However, those skilled in the art will understand that the following examples are for illustrative purposes only and should not be considered as limiting the scope of the invention. Unless otherwise specified in the examples, conventional conditions or conditions recommended by the manufacturer are followed. Unless otherwise specified, the strains, reagents, or instruments used are all commercially available conventional products.

[0112] Example 1

[0113] (1) Whole soybean enzyme inactivation: Place whole soybeans in an oven and heat them at 180℃ for 6 minutes. After the oven is finished, let them cool naturally and then use a soybean peeling machine to peel them.

[0114] (2) Grinding: Grind the peeled soybeans obtained in step (1) into a paste, control the soybean-to-water ratio to be 1:8, use water at 90°C, and keep dissolved oxygen in the water at 3 ppm. After grinding for 30 minutes, filter to obtain soybean milk base.

[0115] (3) Ingredients: Adjust the protein concentration of the soybean milk base to 3%, add 9% sucrose, 0.8% starch, 0.05% salt, 1% dietary fiber and 0.15% pectin, shear for 15 min and mix well, adjust pH to 6.5, homogenize at 25 MPa pressure at 60℃, sterilize at 95℃ for 5 min, and cool to obtain fermentation base.

[0116] (4) Fermentation:

[0117] Using 50 parts by weight of fermentation base as the first soy milk, cooling it to 37°C, and adding 0.2 U / L of the first fermentation bacteria, which included Lactobacillus bulgaricus and Streptococcus thermophilus (with a live bacteria ratio of 3:7), anaerobic fermentation was carried out for 8 hours until the fermentation endpoint of pH 4.7 was reached, thus obtaining the first fermentation product.

[0118] 50 parts by weight of the fermentation base were used as the second soy milk. The other half of the fermentation base was cooled to 28°C, and a second fermentation bacteria were added. The second fermentation bacteria used was Kluyveromyces macrocephala at a concentration of 0.01 U / L. Anaerobic fermentation was carried out for 8 hours to obtain the second fermentation product.

[0119] The first and second fermentation products were aseptically mixed, heated to 37°C, and fermented aerobically for 3 hours until the pH reached below 4.4, which yielded the third fermentation product.

[0120] (5) Post-fermentation treatment:

[0121] The third fermentation product was cooled and demulsified, and the pH was adjusted to 4.3 to obtain soy yogurt (live culture type).

[0122] Comparative Example 1A

[0123] The difference between Comparative Example 1A and Example 1 is that the whole soybean enzyme inactivation step was not performed. Comparative Example 1 directly ground whole soybeans. Other steps and parameters were the same as in Example 1, resulting in soy yogurt (live culture type).

[0124] Comparative Example 1B

[0125] The difference between Comparative Example 1B and Example 1 lies in step (4) fermentation. In Comparative Example 2:

[0126] 100 parts by weight of fermentation base material was used as the first soy milk, cooled to 37°C, and 0.2 U / L of the first fermentation bacteria (same as in Example 1) was added. Anaerobic fermentation was carried out for 8 hours until the fermentation endpoint pH 4.7 was reached, and the first fermentation product was obtained.

[0127] The first fermentation product is cooled and demulsified, and the pH is adjusted to 4.3 to obtain soy yogurt (live culture type).

[0128] Example 2

[0129] (1) Whole soybean enzyme inactivation: Place whole soybeans in an oven and heat them at 180℃ for 6 minutes. After the oven is finished, let them cool naturally and then use a soybean peeling machine to peel them.

[0130] (2) Grinding: Grind the peeled soybeans obtained in step (1) into a paste, control the soybean-to-water ratio to be 1:8, use water at 95°C, and keep dissolved oxygen in the water at 3 ppm. After grinding for 25 minutes, filter to obtain soybean milk base.

[0131] (3) Ingredients: Adjust the protein concentration of the soy milk base to 4%, add 6% sucrose, 0.8% starch and 1% dietary fiber, cut for 15 min and mix well, adjust pH to 6.5, homogenize at 25 MPa pressure at 60℃, sterilize at 95℃ for 5 min, and cool to obtain fermentation base;

[0132] (4) Fermentation:

[0133] Using 50 parts by weight of fermentation base as the first soy milk, cooling it to 42℃, and adding 0.2 U / L of the first fermentation bacteria, which included Lactobacillus bulgaricus and Streptococcus thermophilus (the ratio of their viable counts was 3:7), anaerobic fermentation was carried out for 6 hours until the fermentation endpoint of pH 4.6 was reached, and the first fermentation product was obtained.

[0134] Using 50 parts by weight of fermentation base as the second soy milk, cooling to 25°C, adding the second fermentation bacteria (0.01 U / L of Kluyveromyces macrocephala), and anaerobic fermentation for 6 hours, the second fermentation product was obtained.

[0135] The two fermentation products were aseptically mixed and heated to 37°C for aerobic fermentation for 3 hours, reaching the fermentation endpoint of pH 4.3. The mixture was then cooled to break the emulsion, yielding the third fermentation product.

[0136] (5) Post-fermentation treatment

[0137] Adjust the protein concentration of the third fermentation product obtained in step (4) to 3%, add 2% sucrose, 0.5% pectin and 0.3% soybean polysaccharide, shear for 15 min and mix well, adjust pH to 4.3, homogenize at 25 MPa pressure at room temperature, sterilize at 75℃ for 30 s, cool, and fill to obtain soy yogurt (room temperature drinking type).

[0138] Comparative Example 2A

[0139] The difference between Comparative Example 2A and Example 2 is that the whole soybean enzyme inactivation step was not performed. Comparative Example 1 directly ground whole soybeans. Other steps and parameters were the same as in Example 2.

[0140] Comparative Example 2B

[0141] The difference between Comparative Example 2B and Example 2 lies in step (4) fermentation. In Comparative Example 2B:

[0142] (4) Using 100 parts by weight of fermentation base material as the first soy milk, cooling it to 42°C, adding 0.2 U / L of the first fermentation bacteria (same as in Example 1), and anaerobic fermentation for 6 hours to reach the fermentation endpoint pH 4.6, thus obtaining the first fermentation product.

[0143] (5) Post-fermentation treatment

[0144] Adjust the protein concentration of the first fermentation product obtained in step (4) to 3%, add 2% sucrose, 0.5% pectin and 0.3% soybean polysaccharide, shear for 15 min and mix well, adjust pH to 4.3, homogenize at 25 MPa pressure at room temperature, sterilize at 75℃ for 30 s, cool, and fill to obtain soy yogurt (room temperature drinking type).

[0145] Analysis and testing

[0146] 1. GC-MS was used to determine the volatile flavor compounds in soy yogurt, including beany flavor components (hexanal) and unpleasant sour flavor components (content of 1-octen-3-ol).

[0147] Table 1. Hexanal content (ng / ml) in soy-based yogurt

[0148]

[0149] As shown in Table 1, the hexanal content of the live-culture yogurt in Example 1 was initially detected to be 5.7 ng / ml. The hexanal content increased slightly during the shelf life, but the overall increase was not significant. The hexanal content of the uninactivated raw yogurt in Comparative Example 1A was close to that in Example 1 at the beginning, but the hexanal content on day 35 of the shelf life was about 4.4 times that of Example 1. The hexanal content of Comparative Example 1B was several times higher than that of Example 1 from freshly made to the end of the shelf life.

[0150] As shown in Table 1, the initial hexanal content of the room-temperature soy yogurt prepared in Example 2 was 21.2 ng / ml. During the shelf life, the highest hexanal content was lower than that of the yogurt in Comparative Example 2A, and the hexanal content was significantly lower than that of the yogurt in Comparative Example 2B throughout the entire shelf life.

[0151] Table 2. Content of 1-octen-3-ol in soy-based yogurt (ng / ml)

[0152]

[0153]

[0154] As shown in Table 2, the initial 1-octen-3-ol content of the live-culture yogurt in Example 1 was 1.62 ng / ml, while the 1-octen-3-ol content of the uninactivated yogurt in Comparative Example A was 3.43 ng / ml, which is 2.1 times higher. Furthermore, the 1-octen-3-ol content of the yogurt in Example 1 was consistently lower than that in Comparative Example 1A and Comparative Example 1B throughout its shelf life.

[0155] As shown in Table 2, the initial 1-octen-3-ol content of the room-temperature yogurt in Example 2 was 1.0 ng / ml. During the shelf life, the 1-octen-3-ol content was consistently significantly lower than that of the room-temperature yogurt with uninactivated enzyme raw material in Comparative Example 2A and the conventionally fermented room-temperature yogurt in Comparative Example 2B.

[0156] 2. Sensory evaluation of soy yogurt includes four indicators: color, smell, taste, and overall acceptability, with each indicator scored out of 10.

[0157] Table 3 Sensory scores for soy-based yogurt (live culture type)

[0158]

[0159] *In the table, day 0 and day 35 correspond to day 0 and day 35 of the shelf life, respectively.

[0160] As shown in Table 3, the sensory evaluation of the live-culture soy yogurt prepared in Example 1 was higher than that of commercially available soy yogurt, and its acceptance at the end of its shelf life was higher than that of the live-culture yogurt with uninactivated enzyme raw material in Comparative Example 1A, the soy yogurt fermented by conventional method in Comparative Example 1B, and commercially available soy yogurt.

[0161] Table 4 Sensory ratings of soy yogurt (room temperature type)

[0162]

[0163] *In the table, day 0 and day 35 correspond to day 0 and day 35 of the shelf life, respectively.

[0164] As shown in Table 4, the sensory evaluation of the drinking room-temperature plant-based yogurt prepared in Example 2 was higher than that of commercially available plant-based yogurt, and its acceptance at the end of its shelf life was higher than that of the room-temperature yogurt with uninactivated enzyme raw material in Comparative Example 2A and the conventionally fermented room-temperature yogurt in Comparative Example 2B.

[0165] The experimental results show that, compared with commercially available soy yogurt, the fermentation process in Examples 1-2 significantly reduced the content of undesirable flavor substances in soy yogurt, improved the flavor of soy yogurt, and ensured good flavor retention during shelf life.

[0166] Although specific embodiments of the invention have been described in detail, those skilled in the art will understand that various modifications and variations can be made to the details based on all the teachings disclosed, and all such changes are within the scope of protection of the invention. The full scope of the invention is given by the appended claims and any equivalents thereof.

Claims

1. A method for preparing soy-based yogurt, comprising the following steps: (1) Provide the first soybean milk, inoculate it with the first fermentation bacteria, and carry out anaerobic fermentation. The fermentation endpoint is pH 4-5, and the first fermentation product is obtained. The first fermentation strain is selected from one or more of Streptococcus thermophilus and Lactobacillus bulgaricus; and the fermentation temperature is 37-42℃, and the fermentation time is 6-10h. (2) Provide a second batch of soy milk, inoculate it with a second batch of fermentation bacteria, and carry out anaerobic fermentation for 6-10 hours to obtain the second fermentation product; The second fermentation strain is selected from one or more of Kluyveromyces martensii and Saccharomyces cerevisiae; and the fermentation temperature is 28-37℃; (3) Mix the first fermentation product and the second fermentation product at a weight ratio of 0.8 to 1.2:1, and carry out aerobic fermentation of the mixture until the pH reaches 4-6 to obtain the third fermentation product; and the fermentation temperature is 25-43℃ and the fermentation time is 2-4h. Furthermore, prior to step (1), the process includes the steps of preparing the first soy milk and the second soy milk, specifically including: (a1) The soybean grains are subjected to enzyme inactivation heat treatment; and the enzyme inactivation heat treatment is a dry heat treatment; the temperature of the enzyme inactivation heat treatment is 180℃~240℃; and the time of the enzyme inactivation heat treatment is 2~8min. (a2) Grind and filter the enzyme-inactivated soybeans to obtain soybean milk base; (a3) Pre-treat the soybean milk base material before fermentation to obtain the first soybean milk and the second soybean milk.

2. The method according to claim 1, wherein it has one or more of the following features: In step (1), the protein concentration of the first soy milk is 2%-4%; In step (1), the inoculum amount of fermentation bacteria is 0.1U / L-0.2U / L.

3. The method according to claim 1, wherein it has one or more of the following features: In step (2), the protein concentration of the second soy milk is 2%-4%; In step (2), the inoculum amount of fermentation bacteria is 0.002U / L-0.02U / L.

4. In the method according to claim 1, in step (a1), the beans are whole, unpeeled beans.

5. The method according to claim 1, wherein in step (a1), the bean is a soybean.

6. The method according to claim 1, wherein in step (a2), the pulp has one or more of the following characteristics: (1) The temperature of the water used for grinding is above 80℃; (2) The dissolved oxygen in the grinding water is below 3 ppm; (3) The weight ratio of soybeans to water during grinding is 1:6 to 1:8; (4) The grinding time for the pulp is 15-30 min; (5) Peel the soybeans before grinding them into a paste.

7. The method according to claim 1, wherein step (a3) ​​includes one or more of the following operations: (b1) Regulation of protein concentration; (b2) Add formulation excipients, conditioning excipients, and stabilizers; wherein, The formulation additives are selected from one or more of sugar and fruit juice; the conditioning additives are selected from one or more of starch, salt, fruit pulp, and dietary fiber; the stabilizers are selected from one or more of pectin, carrageenan, gellan gum, agar, or soybean polysaccharides. (b3) Shear and mix; (b4) pH adjustment; (b5) Homogeneous; (b6) Sterilization.

8. The method according to claim 7, wherein the pre-fermentation pretreatment has one or more of the following characteristics: In operation (b1), the protein concentration is adjusted to 2%-4%; In operation (b3), the shearing and mixing time is 10-15 min; In operation (b4), adjust the pH to 6.5-7.0; In operation (b5), homogenization refers to homogenization at 60-70°C using a pressure of 25-35 MPa; In operation (b6), sterilization refers to sterilization at 95°C for 5-15 minutes.

9. The method according to claim 1, further comprising: (4) Perform post-fermentation treatment on the third fermentation product; The post-fermentation treatment includes one or more of the following operations: (c1) Protein concentration regulation; (c2) Add formulation adjuvants, conditioning adjuvants and stabilizers; wherein the formulation adjuvants are selected from one or more of sugar and fruit juice; the conditioning adjuvants are selected from one or more of starch, salt, fruit pulp and dietary fiber; the stabilizers are selected from one or more of pectin, carrageenan, gellan gum, agar or soybean polysaccharide; (c3) Shearing and mixing; (c4) pH adjustment; (c5) Homogeneous; (c6) Sterilization.

10. The method according to claim 9, wherein the post-fermentation treatment has one or more of the following characteristics: In operation (c1), the protein concentration is adjusted to 1%-3%; In operation (c3), the shearing and mixing time is 10-15 min; In operation (c4), adjust the pH to 4.2-4.4; In operation (c5), homogenization refers to homogenization at 60-70°C using a pressure of 10-25 MPa; In operation (c6), sterilization refers to sterilization at 75°C for 20-60 seconds.

11. A soy-based yogurt, prepared by the method described in any one of claims 1-10.

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