Fermentation method for reducing bitter taste of crude soy sauce and soy sauce produced by same

Abstract

The invention discloses a fermentation method capable of reducing bitter taste of soy sauce crude oil and soy sauce produced by the method, gallic acid, p-coumaric acid and sinapic acid are added into the production process of the soy sauce, so that generation of bitter substances such as 5-hydroxymethylfurfural and DDMP in the soy sauce can be obviously reduced, generation of harmful Maillard reaction products is reduced, and the taste of the soy sauce is improved. More beneficial substances are reserved, the taste is more fresh and sweet, the quality of the crude soy sauce is improved, and the production requirements are met; the method is high in fermentation speed, complete in fermentation, simple in preparation method, convenient to operate, low in cost and high in additional value, and has better popularization and application values.

Description

Technical Field

[0001] The invention relates to the technical field of soy sauce production, and in particular to a fermentation method for reducing the bitterness of soy sauce crude oil and soy sauce produced by the method. Background Art

[0002] Soy sauce is a condiment with multiple amino acids and nutrients made from soybeans or defatted soybean meal as the main raw materials, supplemented by starchy raw materials such as flour or wheat, and fermented by microorganisms. The taste of crude soy sauce is mainly salty and umami, supplemented by sweetness, sourness and bitterness. The bitterness of soy sauce mainly comes from the following three aspects: first, the bitter substances contained in salt, second, the bitter amino acids contained in the raw soybeans or soybean meal, and third, the bitter substances produced by the Maillard reaction and caramelization reaction during the fermentation and sterilization of soy sauce. The Maillard reaction accompanies the entire production process of soy sauce; the caramelization reaction reacts violently during the ultra-high temperature (125℃~135℃) sterilization of soy sauce. For example, the reaction of glucose and sweet amino acids lysine or glycine will form bitter substances such as 5-hydroxymethylfurfural and 2,3-dihydro-3,5-dihydroxy-6-methyl-4H-pyran-4-one (DDMP), which not only consumes the original sweet amino acids of soy sauce, but also further increases the bitterness. Soy sauce itself contains a very small amount of phenolic acid substances, but its content is obviously insufficient for the Maillard reaction that exists at all times during the production process of soy sauce. Phenolic acid has antioxidant properties, and can inhibit the degradation induced by glucose and amino groups, reduce the chemical reactions that form bitter substances, and can retain more sweet and umami amino acids and reducing sugars, thereby improving the quality of crude oil. Therefore, it is very necessary to reduce the bitterness produced by the Maillard reaction by adding phenolic acid during the production process of soy sauce. In addition, there is a prior art method that achieves the purpose of removing the bitterness of soy sauce by adding microporous activated carbon and modified carbon fiber to crude oil through adsorption. This technology removes the bitterness in soy sauce by physical adsorption, but it may also reduce the soy sauce flavor in soy sauce, and also increase the production cost of subsequent processes such as ultrafiltration. Therefore, there is a need for an effective fermentation method that can effectively reduce the bitterness of soy sauce. Summary of the invention

[0003] The objective of the present invention is achieved through the following technical solutions:

[0004] A first aspect of the present invention provides a fermentation method for reducing the bitterness of crude soy sauce, comprising the following steps:

[0005] S1 soybean meal cooking: select high-quality defatted soybean meal raw materials that are free of insect bites and mildew, cook them, and then cool them for later use;

[0006] S2 Wheat frying: Fry the wheat using a wheat frying machine, and crush it into 4 to 6 petals after cooling, and set aside;

[0007] S3 inoculation: Mix the soybean meal treated in steps S1 and S2 with the roasted wheat at 35-40° C., inoculate Aspergillus oryzae, and culture at a constant temperature and humidity for 36-48 hours, turn the koji twice every 12-24 hours, and fermentation is completed when the koji material turns yellow-green;

[0008] S4: adding salt water: adding the cooled salt water after boiling to the finished koji, stirring evenly to carry out moromi fermentation;

[0009] S5 staged temperature controlled fermentation:

[0010] S51 The first fermentation stage: the fermentation temperature of the sauce mash is controlled at 15-18°C for 10-20 days, during which the mixture is stirred once a day for 6-15 minutes each time;

[0011] S52 second fermentation stage: on the 30th to 40th day of fermentation, the temperature is raised to 30°C. During this period, on the 25th to 35th day of fermentation, Saccharomyces rouxii is inoculated, gallic acid, p-coumaric acid and sinapinic acid are added, and the constant temperature fermentation is continued for 50 to 60 days;

[0012] S53 third fermentation stage: on the 50th to 60th day of fermentation, the activated Torulopsis yeast is inoculated and the fermentation is continued at a constant temperature for 115 to 120 days. During this period, on the 90th to 95th day of fermentation, gallic acid, p-coumaric acid and sinapinic acid are added and stirred evenly and the fermentation is continued for 115 to 120 days to obtain a fermented mature mash;

[0013] S6: squeezing and filtering: squeezing the mature soy sauce mash to obtain soy sauce residue and soy sauce crude oil;

[0014] S7 sterilization: sterilize the crude soy sauce obtained in S6 at high temperature instantaneously, cool it to below 60°C quickly after sterilization, pump it into a storage tank, store and precipitate it for more than one week for inspection, and pump it into a storage tank after passing the inspection, and obtain the product;

[0015] Further, in step S1, the cooking specifically includes: dry steaming the soybean meal at 100-120° C. for 30-50 min, adding 0.8-1.2 times the mass of the soybean meal and 65-70° C. hot water, rotating and swelling, and then steaming at 110-130° C. for 30-50 min, until the texture is soft, the color is light brown, there is a cooked bean aroma, and it feels soft;

[0016] Furthermore, in step S2, the frying temperature is 280-320° C., and after frying, the wheat is brown, puffed, not burnt, moderately cooked, and has a strong frying wheat aroma;

[0017] Furthermore, in step S3, the mass ratio of soybean meal to fried wheat is 5-7:3-5;

[0018] Furthermore, in step S3, the constant temperature and humidity conditions are 30-32°C and 80-90% relative humidity;

[0019] Further, in S3, the inoculum amount of Aspergillus oryzae is 0.3-0.5w / w% of the raw material;

[0020] Further, in S4, the salt water concentration is 17-18° Bé, and the mass ratio of the finished koji to the salt water is 1:1.5-2.5;

[0021] Furthermore, in S52, the inoculation amount of Saccharomyces rouxii is 0.3-0.8% of the volume of the mash;

[0022] Further, in S52 and S53, after inoculation, the final concentrations of the gallic acid, p-coumaric acid and sinapinic acid are all 3-12 mM / L;

[0023] Furthermore, in S53, the inoculation amount of the Torulopsis yeast is 0.3-0.8% of the volume of the mash;

[0024] Further, in S6, the pressing is performed by a vertical press;

[0025] Furthermore, in S6, the water content of the sauce residue is 20-30% w / w;

[0026] Further, in S7, the high temperature instantaneous sterilization temperature is 128-132°C;

[0027] The second aspect of the present invention provides a low-bitterness soy sauce prepared by any of the above methods;

[0028] The invention can significantly reduce the generation of bitter substances such as 5-hydroxymethylfurfural and DDMP in the soy sauce by adding gallic acid, p-coumaric acid and sinapic acid into the soy sauce production process, reduce the generation of harmful Maillard reaction products, retain more beneficial substances, make the taste more fresh and sweet, improve the quality of the crude soy sauce, and meet the production needs.

[0029] The invention has the advantages of fast fermentation speed, complete fermentation, simple preparation method, convenient operation, low cost, high added value and good promotion and application value. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 Flow chart of the process for preparing soy sauce according to the present invention DETAILED DESCRIPTION

[0031] The present invention is further described below in conjunction with the accompanying drawings and embodiments.

[0032] (I) Embodiment

[0033] Example 1

[0034] A fermentation method for reducing the bitterness of crude soy sauce comprises the following steps:

[0035] S1. Soybean meal cooking: Select high-quality defatted soybean meal raw materials that are free of insect bites and mildew, first dry-steam them at 110℃ for 40 minutes, then add 0.8-1.2 times the mass of the raw materials and 65-70℃ hot water, rotate and swell, then steam them at about 120℃ for 40 minutes, until the texture is soft, the color is light brown with the aroma of cooked beans, and it feels soft, then cool it for use; S2. Wheat frying: The frying temperature is 300℃. After frying, the wheat is brown, puffed, not burnt, moderately cooked, and has a strong aroma of fried wheat. After cooling, grind it into powder 4-6 petals are broken for standby use; S3. Inoculation: At 40°C, the soybean meal treated in steps S1 and S2 is mixed with fried wheat in a raw material mass ratio of 5.5:4.5, and 0.3-0.5% w / w Aspergillus oryzae of the raw material mass is inoculated, and the temperature is 30°C, and the humidity is 80-90% for constant temperature and humidity culture. The koji is turned over once every 12 hours. When the koji material is yellow-green, the fermentation ends and the koji is obtained. The total culture time is about 40 hours; S4. Add salt water: Add the boiled and cooled salt water to the koji, and the salt water concentration is 17~18°Bé, the mass of the salt water is 2 times that of the finished koji, and it is stirred evenly; S5. Temperature-controlled fermentation: the fermentation temperature of the sauce mash is controlled at 15~18℃, and the fermentation is carried out for 10~20 days. During this period, it is stirred once a day, and each time is 10 minutes; after 30~40 days of fermentation, the temperature is raised to 30℃, and the fermentation is carried out at a temperature of 10 minutes. On the 30th day of fermentation, 0.5% of the volume of the sauce mash is inoculated with activated Saccharomyces cerevisiae (commercially available) and gallic acid, p-coumaric acid and sinapinic acid with a final concentration of 3mM / L, respectively. On the 60th day of fermentation, , inoculate 0.5% of the volume of the mash with activated Torulopsis saccharomyces (commercially available), and continue to ferment at a constant temperature for 60 days; ferment for 90 days, keep the temperature below 28°C, add gallic acid, p-coumaric acid and sinapinic acid with a final concentration of 3mM / L on the 90th day of fermentation, stir evenly, and ferment until 120 days to obtain the fermented mature mash; S6. pressing and filtration: the mature mash is pressed by a vertical press to separate the residue and crude oil, obtain the residue with a water content of 25% w / w, and obtain the crude soy sauce oil. S7. Sterilization: sterilize the crude oil obtained in S6 at 128-132℃ for an instant, cool it to below 60℃ quickly after sterilization, pump it into a storage tank, store it for sedimentation for more than one week for inspection, and pump it into a storage tank after passing the inspection. S8. Testing: test the stored crude oil for physical and chemical indicators such as total acid, amino acid nitrogen, reducing sugar, and the amount of free amino acids of bitter substances such as 5-hydroxymethylfurfural and DDMP, and have 10 trained sensory evaluators conduct flavor sensory evaluation.

[0036] Example 2

[0037] A fermentation method for reducing the bitterness of crude soy sauce comprises the following steps:

[0038] S1. Soybean meal cooking: Select high-quality defatted soybean meal raw materials that are free of insect bites and mildew, first dry-steam them at 110℃ for 40 minutes, then add 0.8-1.2 times the mass of the raw materials and 65-70℃ hot water, rotate and swell, and then steam them at about 120℃ for 40 minutes until the texture is soft, light brown in color, with the aroma of cooked beans, and soft to the touch, then cool and set aside; S2. Wheat frying: The frying temperature is 300℃. After frying, the wheat is brown, puffed, not burnt, and has a strong aroma of fried wheat. After cooling, crush 4-6 petals for use; S3. Inoculation: At 35-40℃, mix the soybean meal treated in steps S1 and S2 with the fried wheat. Mix the raw materials at a mass ratio of 5.5:4.5, inoculate 0.3-0.5% w / w Aspergillus oryzae of the raw material mass, culture at a temperature of 30-32°C and a humidity of 80-90% for constant temperature and humidity, turn the koji over every 12 hours, and fermentation is completed when the koji material turns yellow-green, and the total culture time is about 40 hours; S4. Add salt water: add the brine cooled after boiling to the koji, the brine concentration is 17-18°Bé, the brine mass is twice that of the koji, and stir evenly; S5. Temperature-controlled fermentation: the fermentation temperature of the sauce mash is controlled at 15-18°C, and the fermentation is 10-20 days. During this period, stir once a day for 10 minutes each time; ferment for 30-40 minutes. After 30 days, the temperature was raised to 30°C for heat preservation fermentation. On the 30th day of fermentation, 0.5% of the volume of the mash of activated Saccharomyces rouxii (commercially available) and gallic acid, p-coumaric acid and sinapinic acid with a final concentration of 6 mM / L were inoculated. On the 60th day of fermentation, 0.5% of the volume of the mash of activated Torulopsis saccharomyces (commercially available) were inoculated, and the constant temperature fermentation was continued for 60 days; the fermentation was carried out for 90 to 120 days, and the temperature was maintained below 28°C. On the 90th day of fermentation, gallic acid, p-coumaric acid and sinapinic acid with a final concentration of 6 mM / L were added, and the mixture was stirred evenly until the fermentation was carried out for 120 days to obtain the fermented mature mash; S6. Squeezing and filtration: The cooked mash is squeezed by a vertical press to separate the residue from the crude oil, and the residue with a water content of 25% w / w is obtained to obtain the crude soy sauce oil; S7. Sterilization: The crude oil obtained in S6 is sterilized at 128-132°C for an instant, and then quickly cooled to below 60°C after sterilization, and pumped into a storage tank, and stored and precipitated for more than one week for inspection, and then pumped into a storage tank after passing the inspection to obtain the crude oil; S8. Testing: The stored crude oil is tested for physical and chemical indicators such as total acid, amino acid nitrogen, reducing sugar, and the amount of free amino acids of bitter substances such as 5-hydroxymethylfurfural and DDMP, and 10 trained sensory evaluators conduct flavor sensory evaluation;

[0039] Example 3

[0040] A fermentation method for reducing the bitterness of soy sauce crude oil comprises the following steps: S1. soybean meal cooking: selecting high-quality defatted soybean meal raw material without insect bites and mildew, firstly dry-steaming at 110°C for 40 minutes, adding hot water of 0.8 to 1.2 times the mass of the raw material and 65 to 70°C, rotating and swelling, and then steaming at about 120°C for 40 minutes, steaming until the texture is soft, light brown in color, with a cooked bean aroma, soft to the touch, and then cooling for use; S2. wheat frying: the frying temperature is 300°C, and the wheat after frying is tea-colored, puffed, not burnt, and moderately cooked. The product has a strong aroma of roasted wheat. After cooling, it is crushed into 4 to 6 petals for standby use; S3. Inoculation: At 35 to 40°C, the soybean meal treated in steps S1 and S2 is mixed with roasted wheat in a raw material mass ratio of 5.5:4.5, and 0.3 to 0.5% w / w Aspergillus oryzae of the raw material mass is inoculated. The temperature is 30 to 32°C and the humidity is 80 to 90%. The koji is turned over once every 12 hours. When the koji material turns yellow-green, the fermentation is completed and the total cultivation time is about 40 hours; S4. Add salt water: Add the boiled and cooled salt water Add water to the finished koji, the salt water concentration is 17-18°Bé, the mass of the salt water is 2 times that of the finished koji, and stir evenly; S5. Temperature-controlled fermentation: The fermentation temperature of the sauce mash is controlled at 15-18°C, and the fermentation is 10-20 days. During this period, stir once a day for 10 minutes each time; after 30-40 days of fermentation, the temperature is raised to 30°C, and the fermentation is kept warm. On the 30th day of fermentation, 0.5% of the volume of the sauce mash is inoculated with activated Saccharomyces cerevisiae (commercially available) and gallic acid, p-coumaric acid and sinapinic acid with a final concentration of 9mM / L, respectively. After 60 days, inoculate activated Torulopsis yeast (commercially available) with a volume of 0.5% of the mash, and continue to ferment at a constant temperature for 60 days; ferment for 90 to 120 days, keep the temperature below 28°C, add gallic acid, p-coumaric acid and sinapinic acid with a final concentration of 9mM / L on the 90th day of fermentation, stir evenly, and obtain a mature mash after fermentation for 120 days; S6. pressing and filtration: the mature mash is pressed by a vertical press to separate the residue and crude oil, obtain the residue with a water content of 25%w / w, and obtain the crude soy sauce oil. S7. Sterilization: sterilize the crude oil obtained in S6 at 128-132℃ for an instant, cool it to below 60℃ quickly after sterilization, pump it into a storage tank, store it for sedimentation for more than one week for inspection, and pump it into a storage tank after passing the inspection. S8. Testing: test the stored crude oil for physical and chemical indicators such as total acid, amino acid nitrogen, reducing sugar, and the amount of free amino acids of bitter substances such as 5-hydroxymethylfurfural and DDMP, and have 10 trained sensory evaluators conduct flavor sensory evaluation.

[0041] Example 4

[0042] A fermentation method for reducing the bitterness of crude soy sauce comprises the following steps:

[0043] S1. Soybean meal cooking: Select high-quality defatted soybean meal raw materials that are free of insect bites and mildew, first dry-steam them at 110℃ for 40 minutes, then add 0.8-1.2 times the mass of the raw materials and 65-70℃ hot water, rotate and swell, and then steam them at about 120℃ for 40 minutes until the texture is soft, light brown in color, with the aroma of cooked beans, and soft to the touch, then cool and set aside; S2. Wheat frying: The frying temperature is 300℃. After frying, the wheat is brown, puffed, not burnt, and has a strong aroma of fried wheat. After cooling, crush 4-6 petals for use; S3. Inoculation: At 35-40℃, mix the soybean meal treated in steps S1 and S2 with the fried wheat. Mix the raw materials at a mass ratio of 5.5:4.5, inoculate 0.05% w / w Aspergillus oryzae of the raw material mass, culture at a temperature of 30-32°C and a humidity of 80-90% for constant temperature and humidity, turn the koji over once every 12 hours, and fermentation is completed when the koji material turns yellow-green, and the total culture time is about 40 hours; S4. Add salt water: add the boiled and cooled salt water to the finished koji, the salt water concentration is 17-18°Bé, the salt water mass is 2 times that of the finished koji, and stir evenly; S5. Temperature-controlled fermentation: the fermentation temperature of the sauce mash is controlled at 15-18°C, and the fermentation is 10-20 days. During this period, stir once a day for 10 minutes each time; after 30-40 days of fermentation, heat the mixture until the fermentation is complete. The temperature is raised to 30°C for heat preservation fermentation. On the 30th day of fermentation, 0.5% of the volume of the mash of activated Saccharomyces rouxii (commercially available) and gallic acid, p-coumaric acid and sinapinic acid with a final concentration of 12 mM / L are inoculated. On the 60th day of fermentation, 0.5% of the volume of the mash of activated Torulopsis saccharomyces (commercially available) are inoculated, and the constant temperature fermentation is continued for 60 days; for 90 to 120 days of fermentation, the temperature is maintained below 28°C, and on the 90th day of fermentation, gallic acid, p-coumaric acid and sinapinic acid with a final concentration of 12 mM / L are added, and the mixture is stirred evenly until the fermentation is 120 days to obtain the fermented mature mash; S6. Squeeze and filter: The cooked soy sauce mash is squeezed by a vertical press to separate the soy sauce residue and the crude oil, and the soy sauce residue with a water content of 25% w / w is obtained to obtain the soy sauce crude oil; S7. Sterilization: The crude oil obtained in S6 is sterilized at a high temperature of 128-132°C for an instant, and then quickly cooled to below 60°C after sterilization, pumped into a storage tank, and stored and precipitated for more than one week for inspection. After passing the inspection, it is pumped into a storage tank to obtain the soy sauce; S8. Testing: The stored crude oil is tested for physical and chemical indicators such as total acid, amino acid nitrogen, reducing sugar, and the amount of free amino acids of bitter substances such as 5-hydroxymethylfurfural and DDMP, and 10 trained sensory evaluators conduct flavor sensory evaluation.

[0044] (II) Comparative Example

[0045] Comparative Example 1: Gallic acid, p-coumaric acid and sinapinic acid were added only at day 30 of fermentation

[0046] A fermentation method for reducing the bitterness of crude soy sauce comprises the following steps:

[0047] S1. Soybean meal cooking: Select high-quality defatted soybean meal raw materials that are free of insect bites and mildew, first dry-steam them at 110℃ for 40 minutes, then add 0.8-1.2 times the mass of the raw materials and 65-70℃ hot water, rotate and swell, then steam them at about 120℃ for 40 minutes, steam until the texture is soft, light brown in color with the aroma of cooked beans, soft to the touch, then cool and set aside; S2. Wheat frying: The frying temperature is 300℃. After frying, the wheat is brown, puffed, not burnt, moderately cooked, and has a strong aroma of fried wheat. After cooling, crush it into 4-6 petals and set aside; S3. Inoculation: At 35-40°C, the soybean meal treated in steps S1 and S2 and the fried wheat are mixed at a raw material mass ratio of 5.5:4.5, and 0.3-0.5% w / w Aspergillus oryzae of the raw material mass is inoculated, and the temperature is 30-32°C, and the humidity is 80-90% for constant temperature and humidity culture. The koji is turned over once every 12 hours, and the fermentation ends when the koji material presents a yellow-green color, and the total culture time is about 40 hours; S4. Add salt water: Add the boiled and cooled salt water to the koji, the salt water concentration is 17-18°Bé, and the mass of the salt water is twice that of the koji, and stir evenly;

[0048] S5. Temperature-controlled fermentation: the fermentation temperature of the mash is controlled at 15-18°C, and the fermentation is carried out for 10-20 days, during which the mixture is stirred once a day for 10 minutes each time; after 30-40 days of fermentation, the temperature is raised to 30°C, and the fermentation is kept warm. On the 30th day of fermentation, 0.5% of the volume of the mash of activated Saccharomyces cerevisiae (commercially available) and gallic acid, p-coumaric acid and sinapinic acid with a final concentration of 9 mM / L are inoculated; on the 60th day of fermentation, 0.5% of the volume of the mash of activated Torulopsis cerevisiae (commercially available) are inoculated, and the fermentation is continued at a constant temperature for 60 days; the fermentation is carried out for 90-120 days, and the temperature is maintained below 28°C until the fermentation is carried out for 120 days to obtain the fermented mature mash; S6. Pressing and filtration: the mature mash is pressed by a vertical press to separate the residue and crude oil, to obtain the residue with a water content of 25% w / w, and to obtain crude soy sauce oil. S7. Sterilization: sterilize the crude oil obtained in S6 at 128-132℃, cool it to below 60℃ quickly after sterilization, pump it into a storage tank, store it for precipitation for more than one week, and then inspect it. After passing the inspection, pump it into the storage tank to obtain the crude oil; S8. Testing: test the total acid, amino acid nitrogen, reducing sugar and other physical and chemical indicators of the stored crude oil, and the amount of free amino acids of bitter substances such as 5-hydroxymethylfurfural and DDMP, and have 10 trained sensory evaluators conduct flavor sensory evaluation;

[0049] Comparative Example 2: Gallic acid, p-coumaric acid and sinapinic acid were added only at day 90 of fermentation

[0050] A fermentation method for reducing the bitterness of crude soy sauce comprises the following steps:

[0051] S1. Soybean meal cooking: Select high-quality defatted soybean meal raw materials that are free of insect bites and mildew, first dry-steam them at 110℃ for 40 minutes, then add 0.8-1.2 times the mass of the raw materials and 65-70℃ hot water, rotate and swell, and then steam them at about 120℃ for 40 minutes, until the texture is soft, the color is light brown with the aroma of cooked beans, and it feels soft, then cool it for use; S2. Wheat frying: The frying temperature is 300℃. After frying, the wheat is tea-colored, puffed, not burnt, and has a strong aroma of fried wheat. After cooling, crush it into 4-6 petals for use; S3. Inoculation: Inoculate the wheat that has been treated in steps S1 and S2 at 35-40℃. The soybean meal and the fried wheat are mixed in a raw material mass ratio of 5.5:4.5, and 0.3-0.5% w / w Aspergillus oryzae mass of the raw materials is inoculated. The temperature is 30-32°C and the humidity is 80-90% for constant temperature and humidity culture. The koji is turned over once every 12 hours. When the koji material turns yellow-green, the fermentation is completed and the total culture time is about 40 hours; S4. Adding salt water: Adding the brine cooled after boiling to the koji, the concentration of the brine is 17-18°Bé, the mass of the brine is twice that of the koji, and stirring is uniform; S5. Temperature-controlled fermentation: The temperature of the sauce fermentation is controlled at 15-18°C, and the fermentation is 10-20 days. During this period, stirring is done once a day, and each time 10min; after 30 to 40 days of fermentation, the temperature is raised to 30°C for heat preservation fermentation. On the 30th day of fermentation, 0.5% of the volume of the mash of activated Saccharomyces rouxii (commercially available) is inoculated. On the 60th day of fermentation, 0.5% of the volume of the mash of activated Torulopsis saccharomyces cerevisiae (commercially available) is inoculated, and the constant temperature fermentation is continued for 60 days; for 90 to 120 days of fermentation, the temperature is maintained below 28°C, and gallic acid, p-coumaric acid and sinapinic acid with a final concentration of 9mM / L are added on the 90th day of fermentation, and the mixture is stirred evenly until the fermentation is 120 days to obtain the fermented mature mash; S6. Squeezing and filtration: The mature mash is subjected to vertical filtration The press is used to separate the soy sauce residue and the crude oil, and the soy sauce residue with a water content of 25% w / w is obtained to obtain the soy sauce crude oil; S7. Sterilization: The crude oil obtained in S6 is sterilized at a high temperature of 128-132°C, and then quickly cooled to below 60°C after sterilization, and pumped into a storage tank, and stored and precipitated for more than one week for inspection. After passing the inspection, it is pumped into the storage tank to obtain the soy sauce; S8. Testing: The stored crude oil is tested for physical and chemical indicators such as total acid, amino acid nitrogen, reducing sugar, and the amount of free amino acids of bitter substances such as 5-hydroxymethylfurfural and DDMP, and 10 trained sensory evaluators conduct flavor sensory evaluation;

[0052] Comparative Example 3: Gallic acid, p-coumaric acid and sinapinic acid were not added during the fermentation process

[0053] A fermentation method for reducing the bitterness of crude soy sauce comprises the following steps:

[0054] S1. Soybean meal cooking: Select high-quality defatted soybean meal raw materials that are free of insect bites and mildew, first dry-steam them at 110℃ for 40 minutes, then add 0.8-1.2 times the mass of the raw materials and 65-70℃ hot water, rotate and swell, and then steam them at about 120℃ for 40 minutes, until the texture is soft, the color is light brown with the aroma of cooked beans, and it feels soft, then cool it for use; S2. Wheat frying: The frying temperature is 300℃. After frying, the wheat is brown, puffed, not burnt, and has a strong aroma of fried wheat. After cooling, crush it into 4-6 petals for use; S3. Inoculation: Inoculate the wheat that has been through the steps at 35-40℃. The soybean meal treated in step S1 and S2 is mixed with the fried wheat in a raw material mass ratio of 5.5:4.5, and 0.3-0.5% w / w Aspergillus oryzae of the raw material mass is inoculated. The temperature is 30-32°C and the humidity is 80-90% for constant temperature and humidity culture. The koji is turned over once every 12 hours. When the koji material turns yellow-green, the fermentation is completed and the total culture time is about 40 hours; S4. Adding salt water: Adding the boiled and cooled salt water to the finished koji, the salt water concentration is 17-18°Bé, the salt water mass is twice that of the finished koji, and stirring evenly; S5. Temperature-controlled fermentation: The fermentation temperature of the sauce mash is controlled at 15-18°C, Fermentation is carried out for 10 to 20 days, during which stirring is carried out once a day for 10 minutes each time; after fermentation for 30 to 40 days, the temperature is raised to 30°C for heat preservation fermentation, and on the 30th day of fermentation, 0.5% of the volume of the mash of activated Saccharomyces cerevisiae (commercially available) is inoculated, and on the 60th day of fermentation, 0.5% of the volume of the mash of activated Torulopsis cerevisiae (commercially available) is inoculated, and constant temperature fermentation is continued for 60 days; fermentation is carried out for 90 to 120 days, and the temperature is maintained below 28°C until the fermentation is carried out for 120 days to obtain the fermented mature mash; S6. pressing and filtration: the mature mash is pressed by a vertical press to achieve Separation of the soy sauce residue and crude oil to obtain the soy sauce residue with a water content of 25% w / w, and obtain the soy sauce crude oil; S7. Sterilization: sterilize the crude oil obtained in S6 at a high temperature of 128-132°C, quickly cool it to below 60°C after sterilization, pump it into a storage tank, store it for precipitation for more than one week for inspection, and pump it into a storage tank after passing the inspection to obtain the soy sauce; S8. Testing: The stored crude oil is tested for physical and chemical indicators such as total acid, amino acid nitrogen, reducing sugar, and the amount of free amino acids of bitter substances such as 5-hydroxymethylfurfural and DDMP, and 10 trained sensory evaluators conduct flavor sensory evaluation.

[0055] Table 1 Effects of adding different contents of gallic acid, p-coumaric acid and sinapinic acid on the basic indicators of soy sauce

[0056]

[0057] Table 2 Effects of adding different amounts of gallic acid, p-coumaric acid and sinapic acid on bitter substances in soy sauce

[0058]

[0059] Note: In Table 2, 5-HMF content in soy sauce was determined by liquid chromatography-mass spectrometry (HPLC-MS); headspace solid phase microextraction-gas chromatography-mass spectrometry (SPME-GC-MS) was used to detect the main bitter substances in the other three soy sauces.

[0060] Table 3 Effects of adding different amounts of gallic acid, p-coumaric acid and sinapinic acid on free amino acids in soy sauce

[0061]

[0062] Table 4 Effects of adding different amounts of gallic acid, p-coumaric acid and sinapinic acid on the taste and flavor of soy sauce

[0063]

[0064]

[0065] From the experimental results of the examples, it can be seen that adding gallic acid, p-coumaric acid and sinapinic acid into the soy sauce production process can significantly reduce the generation of bitter substances such as 5-hydroxymethylfurfural and DDMP in the soy sauce, reduce the bitter substances produced by the Maillard reaction, retain more beneficial substances, make the taste sweeter, and improve the quality of the crude soy sauce.

[0066] Although the present invention has been described above with reference to the embodiments, various modifications may be made thereto and parts thereof may be replaced with equivalents without departing from the scope of the present invention. In particular, as long as there is no structural conflict, the various features in the embodiments disclosed in the present invention may be used in combination with each other in any manner, and the fact that these combinations are not exhaustively described in this specification is only for the sake of omitting space and saving resources. Therefore, the present invention is not limited to the specific embodiments disclosed herein, but includes all technical solutions falling within the scope of the claims.

Claims

1. A fermentation method for reducing the bitterness of crude soy sauce, characterized in that: The following steps are involved: S1 soybean meal cooking: select high-quality defatted soybean meal raw materials that are free of insect bites and mildew, cook them, and then cool them for later use; S2 Wheat frying: Fry the wheat using a wheat frying machine, and crush it into 4 to 6 petals after cooling, and set aside; S3 inoculation: the soybean meal treated in step S1 and S2 is mixed with the roasted wheat at 35-40°C, inoculated with Aspergillus oryzae, cultured at a constant temperature and humidity for 36-48 hours, turned over twice every 12-24 hours, and the fermentation is completed when the koji material turns yellow-green; S4: adding salt water: adding the cooled salt water after boiling to the finished koji, stirring evenly to carry out moromi fermentation; S5 staged temperature controlled fermentation: S51 The first fermentation stage: the fermentation temperature of the sauce mash is controlled at 15-18°C for 10-20 days, during which the mixture is stirred once a day for 6-15 minutes each time; S52 second fermentation stage: on the 30th to 40th day of fermentation, the temperature is raised to 30°C. During this period, on the 25th to 35th day of fermentation, Saccharomyces cerevisiae is inoculated, gallic acid, p-coumaric acid and sinapinic acid are added, and the constant temperature fermentation is continued for 50 to 60 days; S53 third fermentation stage: on the 50th to 60th day of fermentation, the activated Torulopsis yeast is inoculated and fermented at a constant temperature for 115 to 120 days. During this period, on the 90th to 95th day of fermentation, gallic acid, p-coumaric acid and sinapinic acid are added and stirred evenly and fermented for 115 to 120 days to obtain a fermented mature mash; further, in S53, the inoculation amount of the Torulopsis yeast is 0.3 to 0.8% of the volume of the mash; S6: squeezing and filtering: squeezing the mature mash to obtain soy sauce residue and soy sauce crude oil; further, in S6, the squeezing is performed using a vertical press; further, in S6, the soy sauce residue has a water content of 20-30% w / w; S7 sterilization: subject the soy sauce crude oil obtained in S6 to high-temperature instantaneous sterilization, rapidly cool it to below 60°C after sterilization, pump it into a storage tank, store and precipitate it for more than one week for inspection, and pump it into a storage tank after passing the inspection; further, in S7, the high-temperature instantaneous sterilization temperature is 128-132°C.

2. The fermentation method for reducing the bitterness of crude soy sauce according to claim 1, characterized in that: In step S1, the cooking specifically includes: dry-steaming the soybean meal at 100-120° C. for 30-50 min, adding hot water at 65-70° C., which is 0.8-1.2 times the mass of the soybean meal, and then steaming at 110-130° C. for 30-50 min after rotation swelling, until the texture is soft, the color is light brown, there is a cooked bean aroma, and it feels soft.

3. The fermentation method for reducing the bitterness of crude soy sauce according to claim 1, characterized in that: In step S2, the frying temperature is 280-320°C, and after frying, the wheat is brown, puffed, not burnt, moderately cooked, and has a strong fried wheat aroma.

4. The fermentation method for reducing the bitterness of crude soy sauce according to claim 1, characterized in that: In step S3, the mass ratio of the soybean meal to the fried wheat is 5-7:3-5.

5. The fermentation method for reducing the bitterness of crude soy sauce according to claim 1, characterized in that: In step S3, the constant temperature and humidity conditions are a temperature of 30-32° C. and a relative humidity of 80-90%.

6. The fermentation method for reducing the bitterness of crude soy sauce according to claim 1, characterized in that: In step S3, the inoculum amount of Aspergillus oryzae is 0.3-0.5w / w% of the raw material.

7. The fermentation method for reducing the bitterness of crude soy sauce according to claim 1, characterized in that: In step S4, the concentration of the brine is 17-18° Bé, and the mass ratio of the finished koji to the brine is 1:1.5-2.

5.

8. The fermentation method for reducing the bitterness of crude soy sauce according to claim 1, characterized in that: In step S52, the inoculation amount of the Saccharomyces rouxii is 0.3-0.8% of the volume of the mash.

9. The fermentation method for reducing the bitterness of crude soy sauce according to claim 1, characterized in that: In steps S52 and S53, after inoculation, the final concentrations of the gallic acid, p-coumaric acid and sinapinic acid are all 3-12 mM / L.

10. A low-bitterness soy sauce prepared by the fermentation method according to any one of claims 1 to 9.

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