A temperature-controlled acetic acid fermentation method and its application

Abstract

The present invention belongs to the technical field of vinegar brewing, and discloses a method for temperature-controlled acetic fermentation and its application. The present invention is to mix auxiliary materials, wine mash, and acetic acid fermentation bacteria to form a vinegar mash, and then carry out acetic fermentation; the entire acetic fermentation is divided into three fermentation stages: the front, middle, and back stages, and the fermentation temperature is controlled in each stage. In the early fermentation stage and the middle fermentation stage, the fermentation temperature is controlled at 34-40°C. When the temperature naturally drops to 34°C, it is heated to 40°C within 1 hour, and ventilation and turning of the mash are carried out during this period; in the back fermentation stage, the temperature of the vinegar mash is controlled to 34-40°C during this period, and ventilation and turning of the mash are carried out during this period; when the alcohol content in the vinegar mash is lower than 0.5 g / 100 g, and the acetic acid concentration remains unchanged, the fermentation is terminated. The method provided by the present invention is applicable to the acetic acid stage of vinegar production by solid-state fermentation, can significantly improve the flavor of vinegar, improve production efficiency, and has broad application prospects and promotion value.

Description

Technical Field

[0001] The invention belongs to the technical field of vinegar brewing and discloses a temperature-variable controlled acetic acid fermentation method and application thereof. Background Art

[0002] Vinegar is a traditional fermented condiment in my country, boasting a long history and a rich variety. Vinegar brewing methods primarily include solid-state fermentation and liquid-state fermentation. Solid-state fermentation, however, has become the primary method for preparing traditional vinegars (such as Shanxi aged vinegar and Zhenjiang fragrant vinegar) due to its ability to better preserve traditional flavor compounds and develop a unique, complex aroma. The acetic acid fermentation stage of solid-state fermentation primarily utilizes acetic acid bacteria to oxidize ethanol in the mash into acetic acid. Simultaneously, the synergistic action of various microorganisms produces lactic acid, amino acids, acetoin, and other key substances that determine the flavor, taste, and nutritional value of vinegar. Therefore, solid-state fermentation plays a crucial role in the final quality of the vinegar.

[0003] At present, most companies use mechanized and automated control methods to carry out solid-state fermentation of vinegar, and improve production efficiency by controlling the acetic acid fermentation stage in the solid-state fermentation in stages. Although this method optimizes the fermentation process to a certain extent, the growth and metabolic activity of associated bacteria (such as lactic acid bacteria and Bacillus) are limited, and the product quality, raw material utilization efficiency and fermentation rate still need to be improved. Summary of the Invention

[0004] To address these shortcomings, this invention provides a temperature-controlled acetic acid fermentation method and its application. This method divides acetic acid fermentation into three stages and controls the fermentation temperature in each stage to enhance the activity of key microorganisms, improve fermentation efficiency, and enhance the flavor quality of the vinegar.

[0005] To achieve the above objectives, the present invention provides the following technical solutions:

[0006] In a first aspect, the present invention provides a method for temperature-controlled acetic acid fermentation, characterized in that it comprises the following steps:

[0007] S1: mixing wine mash with auxiliary materials to obtain fermentation raw materials; inoculating acetic acid fermentation bacteria into the fermentation raw materials and stirring them evenly to obtain vinegar mash;

[0008] S2: The vinegar mash undergoes acetic acid fermentation in a solid-state fermentation container: in the early fermentation stage, the fermentation time is 5 days, the vinegar mash is heated to 40°C within 1 hour at the beginning of fermentation, and when the temperature naturally drops to 34°C, the temperature is raised to 40°C within 1 hour, and ventilation and turning are carried out during this period; in the middle fermentation stage, the fermentation time is 5 days, the temperature of the vinegar mash is controlled to be 34-40°C during this period, and when the temperature of the vinegar mash naturally drops to 34°C, the temperature is raised to 40°C within 1 hour, and ventilation and turning are carried out during this period; in the late fermentation stage, the temperature of the vinegar mash is controlled to be 34-40°C during this period, and ventilation and turning are carried out during this period; the fermentation is terminated when the alcohol content in the vinegar mash is lower than 0.5 g / 100 g vinegar mash and the acetic acid concentration remains unchanged.

[0009] In the present method, the temperature control method for the early and middle stages of acetic acid fermentation is rapid heating followed by natural cooling. Rapid, controllable heating intervention is performed at the trigger heating point (34°C) to quickly raise the temperature to the target high temperature (40°C), and then allowed to naturally cool to the trigger heating point. The temperature of the mash in the middle layer of the solid-state fermentation vessel can be continuously monitored in real time to represent the mash temperature. During the acetic acid fermentation process, the mash temperature naturally decreases because the heat generated by microbial activity is less than the ambient heat dissipation, and ventilation or turning the mash also has a cooling effect. Rapid heating is achieved by heating intervention to raise the mash temperature to the target high temperature within a short period of time (1 hour).

[0010] In the method of the present invention, the "solid-state fermentation container" refers to a special equipment used to carry vinegar mash and provide a suitable environment for acetic acid fermentation, including but not limited to traditional fermentation tanks and solid-state fermentation tanks.

[0011] In the method of the present invention, the "acetic acid fermentation bacteria" refers to microorganisms used in the acetic acid fermentation stage of vinegar, including but not limited to acetic acid bacteria, lactic acid bacteria and Bacillus, which can be introduced in the form of vinegar mash, Daqu, bran qu, pure strain bacterial agent or composite bacterial agent.

[0012] In the method of the present invention, the "auxiliary materials" refer to the auxiliary materials used in brewing vinegar, including but not limited to bran, rice chaff, rice husk and soybean meal.

[0013] In the method of the present invention, the "wine mash" refers to the key intermediate product in the process of brewing vinegar, specifically refers to the liquid or semi-liquid mixture containing alcohol, residual sugar, incompletely decomposed starch, protein, microorganisms and grain particles formed after grains (such as rice, glutinous rice, sorghum, etc.) are steamed, saccharified, and fermented with alcohol.

[0014] Preferably, the temperature of the mash during the late fermentation stage in step S2 is controlled to be 34-36°C, and when the temperature of the mash naturally drops to 34°C, it is heated to 36°C within 1 hour.

[0015] Dynamic temperature control (shaking culture at 34-36°C) is used in the later fermentation stage to promote the enrichment of total acid and key flavor substance acetoin in the vinegar mash.

[0016] More preferably, the temperature raising method in step S2 is to heat the solid-state fermentation container using hot circulating water.

[0017] Preferably, the aeration rate of the aeration and turning of the mash during the early fermentation stage, the middle fermentation stage and the late fermentation stage in step S2 is 5-7 lpm.

[0018] More preferably, the ventilation rate is 5 lpm.

[0019] Preferably, during the early fermentation stage and the mid-fermentation stage in step S2, ventilation and stirring of the mash are performed every 8-12 hours; the duration of the ventilation and stirring of the mash is 20 minutes.

[0020] Preferably, ventilation and turning of the mash are continuously performed during the late fermentation stage in step S2.

[0021] More preferably, the rotation speed of the ventilation and stirring mash is 3 rpm.

[0022] In a second aspect, the present invention further provides an application of the above-mentioned temperature-variable controlled acetic acid fermentation method in the production of vinegar by solid-state fermentation.

[0023] In a third aspect, the present invention also provides vinegar prepared by the above-mentioned temperature-controlled acetic acid fermentation method.

[0024] Beneficial effects:

[0025] This invention proposes a process improvement for the acetic acid fermentation stage of traditional vinegar solid-state fermentation. The core approach is to divide the acetic acid fermentation stage into three stages: early, middle, and late fermentation, and implement dynamic temperature control. This strategy of rapid temperature increase and natural cooling during the early and middle stages effectively stimulates the activity of acetic acid bacteria and lactic acid bacteria, achieving rapid ignition and increasing acid production. It also maintains high microbial activity during the mid-stage, stimulating the production of lactic acid, reducing sugars, and amino acid nitrogen.

[0026] This method not only greatly improves fermentation efficiency and product quality, but also ensures strong controllability of the entire fermentation process and stability of product quality by precisely controlling temperature, ventilation and turning over in stages. DETAILED DESCRIPTION

[0027] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the embodiments described are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0028] Unless otherwise specified, the percentage sign "%" in the examples refers to the mass percentage of solids, the percentage of solutions refers to the grams of solute contained in 100 mL, and the percentage of liquids refers to the volume ratio of the solutions at 25°C.

[0029] The test materials used in the present invention are all common commercial products and can be purchased in the market.

[0030] The Daqu comes from Shanxi Zilin Vinegar Co., Ltd., and the active dry yeast is a high-temperature resistant active dry yeast, which comes from Angel Yeast Co., Ltd.

[0031] The acetic acid fermentation bacteria used in the embodiment of the present invention are Lactobacillus helveticus ( Lactobacillus helveticus )0-6, Lactobacillus fermentum ( Lactobacillus fermentum ) 1-5, Lactobacillus plantarum ( Lactobacillus plants ) 1.2437, Pediococcus pentosaceus ( Pediococcus pentosaceus ) AAF1-3, Acetobacter pasteurianus ( Acetobacter pasteurianus ) A11 and Bacillus amyloliquefaciens ( Bacillus amyloliquefaciens )G2-9. These strains were screened from vinegar fermentation and deposited in the Microbial Pharmaceutics Laboratory of Tianjin University of Science and Technology. These strains have been published in "Construction of Artificial Microbial Community and Optimization of Fermentation Process for Solid-State Fermentation of Vinegar" (Zhao Cuimei, Master's thesis, 2021).

[0032] The culture medium used in the embodiments of the present invention is:

[0033] MRS medium (w / v): glucose 2%, casein 1%, beef powder 0.8%, yeast powder 0.5%, anhydrous sodium acetate 0.5%, triammonium citrate 0.2%, dipotassium hydrogen phosphate 0.2%, cysteine ​​hydrochloride 0.05%, magnesium sulfate 0.02%, manganese sulfate 0.005%, Tween 80 0.1%, and the rest is water. The pH was adjusted to 5.2.

[0034] GY medium (w / v): glucose 2%, yeast extract 2%, ethanol 3.5% (v / v), and the rest water.

[0035] LB medium (w / v): peptone 1%, yeast extract 0.5%, NaCl 1%, and the rest water.

[0036] The determination method involved in the embodiments of the present invention is:

[0037] Sample pretreatment methods were based on the methods described in the paper "Optimization of Solid-State Fermentation Conditions and Fermentation Kinetics Analysis of Vinegar" (by Li Xiaowei). Total acid and amino acid nitrogen were determined according to the standard methods of GB / T 19777-2013, "Geographical Indication Product, Shanxi Aged Vinegar." Ethanol content was determined using a SBA biosensor, reducing sugars were determined using the DNS method, and acetoin was determined according to QB / T 4234-2011 3-Hydroxy-2-Butanone (Acetoin). Acetic acid, lactic acid, and raw material utilization were determined according to the methods described in the paper "Optimization of Solid-State Fermentation Conditions and Fermentation Kinetics Analysis of Vinegar" (by Li Xiaowei).

[0038] Example 1

[0039] This embodiment provides a method for producing traditional vinegar by using a temperature-controlled acetic acid fermentation method.

[0040] (1) Raw material processing: Grind the dried sorghum into 40 meshes using a grinder and put it into the saccharification cylinder, then add 88-90℃ water-moistened material for 8 hours.

[0041] (2) Liquefaction and saccharification: Add high-temperature resistant α-amylase at a ratio of 1000 U / kg to the moistened sorghum, keep it warm at 88-90℃ for 20 min to form a mash; when the temperature of the mash drops below 62℃, add 1500 U / kg of saccharifying enzyme and keep it warm at 58-62℃ for 1 h.

[0042] (3) Mixing the koji: Lower the temperature of the mash to 28-32°C, add daqu to the mash at a mass ratio of sorghum to daqu of 1:0.625, and then add water to a material-water ratio of 1:3.3; inoculate active dry yeast into the mash at an inoculum rate of 2‰ (rehydrate and activate at 35-37°C for 30 min).

[0043] (4) Alcohol fermentation: The mash was placed in a wine vat (50 L), opened on the first day, and kept closed for the rest of the fermentation time. The fermentation temperature was maintained at 28-30 °C. The alcohol fermentation was terminated when the ethanol content in the mash was 7.0% (w / w) and the total acid content was 1.5 g / 100 g.

[0044] (5) Preparation of acetic acid fermentation strains: Take out the strain preservation liquid from the -80℃ refrigerator, among which Lactobacillus helveticus 0-6, Lactobacillus fermentum 1-5, Lactobacillus plantarum 1.2437, and Pediococcus pentosaceus AAF1-3 were inoculated at 2% in 5 mL of MRS culture medium and cultured at 37℃ for 12 h; Acetobacter pasteurianus A11 was inoculated at 2% in 5 mL of GY culture medium and cultured at 30℃ and 180 rpm for 24 h; Bacillus amyloliquefaciens G2-9 was inoculated at 2% in 5 mL of LB culture medium and cultured at 37℃ and 200 rpm for 12 h. Then, expand the culture, and the above strains were inoculated at 1% in MRS, GY and LB fermentation medium respectively, and cultured under the same conditions. Afterwards, enrich or dilute the strains to make the initial concentration of each strain reach 10 8 The obtained bacterial solution was centrifuged at 3500 r / min and 4°C for 5 min, the supernatant was discarded, and an appropriate amount of sterile saline was added for washing to obtain a pure bacterial solution (10 8 CFU / mL) was used for subsequent fermentation inoculation.

[0045] (6) Preliminary preparation for acetic acid fermentation: Place the wine mash in a rotary drum solid-state fermentation tank, add auxiliary materials according to the mass ratio of wine mash: bran: rice husk = 5:1.1:0.6, stir and mix well, then inoculate the above-mentioned acetic acid fermentation bacteria (the inoculation amount of each strain is 1%) to make vinegar mash. The initial alcohol content of the vinegar mash is 4.5-5.0 g / 100 g vinegar mash, and the moisture content of the vinegar mash is 60%-65%. Start acetic acid fermentation.

[0046] (7) Acetic acid fermentation: in the early fermentation stage, the fermentation time is 5 days. At the beginning of fermentation, the temperature of the fermentation mash in the fermentation tank is first raised to 40℃ in 1 hour by hot circulating water. When the temperature of the fermentation mash in the fermentation tank naturally drops to 34℃, it is heated to 40℃ within 1 hour. During this period, ventilation and mash turning are carried out. The ventilation and mash turning cycle is 8 hours, the ventilation rate is 5 lpm, the ventilation and mash turning time is 20 minutes, and the rotation speed is 3 rpm. In the middle fermentation stage, the fermentation time is 5 days. The fermentation temperature is controlled at 34-40℃ during the period. When the temperature of the fermentation mash in the solid-state fermentation container naturally drops to 34℃, it is heated to 40℃ within 1 hour. During this period, ventilation and mash turning are carried out. The ventilation and mash turning cycle is 12 hours, the ventilation rate is 5 lpm, the ventilation and mash turning time is 20 minutes, and the rotation speed is 3 rpm. In the late fermentation stage, constant temperature fermentation is carried out at 40℃. During this period, ventilation and mash turning are carried out. The ventilation and mash turning cycle is 8 hours. h, aeration rate of 5 lpm, ventilation and turning time of 20 min, rotation speed of 3 rpm; fermentation is terminated when the alcohol content in the vinegar mash is lower than 0.5 g / 100 g vinegar mash and the acetic acid concentration remains unchanged.

[0047] Example 2

[0048] This embodiment provides a method for producing traditional vinegar by using a temperature-controlled acetic acid fermentation method.

[0049] Steps (1) to (6) are the same as in Example 1.

[0050] (7) Acetic acid fermentation: in the early fermentation stage, the fermentation time is 5 days. At the beginning of fermentation, the temperature of the fermentation mash in the fermentation tank is first raised to 40℃ in 1 hour by hot circulating water. When the temperature of the fermentation mash in the fermentation tank naturally drops to 34℃, it is heated to 40℃ within 1 hour. During this period, ventilation and mash turning are carried out. The ventilation and mash turning cycle is 12 hours, the ventilation rate is 5 lpm, the ventilation and mash turning time is 20 minutes, and the rotation speed is 3 rpm. In the middle fermentation stage, the fermentation time is 5 days. The fermentation temperature is controlled at 34-40℃ during this period. When the temperature of the fermentation mash in the solid-state fermentation container naturally drops to 34℃, it is heated to 40℃ within 1 hour. During this period, ventilation and mash turning are carried out. The ventilation and mash turning cycle is 12 hours, the ventilation rate is 5 lpm, the ventilation and mash turning time is 20 minutes, and the rotation speed is 3 rpm. In the late fermentation stage, constant temperature fermentation is carried out at 40℃. During this period, ventilation and mash turning are carried out. The ventilation and mash turning cycle is 12 hours, the ventilation rate is 5 lpm, the ventilation and mash turning time is 20 minutes, and the rotation speed is 3 rpm. h, aeration rate of 5 lpm, ventilation and turning time of 20 min, rotation speed of 3 rpm; fermentation is terminated when the alcohol content in the vinegar mash is lower than 0.5 g / 100 g vinegar mash and the acetic acid concentration remains unchanged.

[0051] Example 3

[0052] This embodiment provides a method for producing traditional vinegar by using a temperature-controlled acetic acid fermentation method.

[0053] Steps (1) to (6) are the same as in Example 1.

[0054] (7) Acetic acid fermentation: in the early fermentation stage, the fermentation time is 5 days. At the beginning of fermentation, the temperature of the fermentation mash in the fermentation tank is first raised to 40℃ in 1 hour by hot circulating water. When the temperature of the fermentation mash in the fermentation tank naturally drops to 34℃, it is heated to 40℃ within 1 hour. During this period, ventilation and turning of the mash are carried out. The ventilation and turning cycle is 8 hours, the ventilation rate is 5 lpm, the ventilation and turning time is 20 minutes, and the rotation speed is 3 rpm. In the middle fermentation stage, the fermentation time is 5 days. The fermentation temperature is controlled at 34-40℃ during the period. When the temperature of the fermentation mash in the solid-state fermentation container naturally drops to 34℃, it is heated to 40℃ within 1 hour. During this period, ventilation and turning of the mash are carried out. The ventilation and turning cycle is 8 hours, the ventilation rate is 5 lpm, the ventilation and turning time is 20 minutes, and the rotation speed is 3 rpm. In the late fermentation stage, fermentation is carried out at a constant temperature of 40℃, and continuous ventilation and turning of the mash are carried out during this period. The ventilation and turning cycle is 8 hours, the ventilation rate is 5 lpm, the ventilation and turning time is 20 minutes, and the rotation speed is 3 rpm. lpm, ventilation and turning time is 20 min, and the rotation speed is 3 rpm; fermentation is terminated when the alcohol content in the vinegar mash is lower than 0.5 g / 100 g vinegar mash and the acetic acid concentration remains unchanged.

[0055] Example 4

[0056] This embodiment provides a method for producing traditional vinegar by using a temperature-controlled acetic acid fermentation method.

[0057] Steps (1) to (6) are the same as in Example 1.

[0058] (7) Acetic acid fermentation: in the early fermentation stage, the fermentation time is 5 days. At the beginning of fermentation, the temperature of the fermentation mash in the fermentation tank is first raised to 40℃ in 1 hour by hot circulating water. When the temperature of the fermentation mash in the fermentation tank naturally drops to 34℃, it is heated to 40℃ within 1 hour. During this period, ventilation and turning of the mash are carried out. The ventilation and turning cycle is 8 hours, the ventilation rate is 5 lpm, the ventilation and turning time is 20 minutes, and the rotation speed is 3 rpm. In the middle fermentation stage, the fermentation time is 5 days. The fermentation temperature is controlled at 34-40℃ during the period. When the temperature of the fermentation mash in the solid-state fermentation container naturally drops to 34℃, it is heated to 40℃ within 1 hour. During this period, ventilation and turning of the mash are carried out. The ventilation and turning cycle is 8 hours, the ventilation rate is 5 lpm, the ventilation and turning time is 20 minutes, and the rotation speed is 3 rpm. rpm; in the later fermentation stage, the fermentation is carried out under shaking at 34-37°C (firstly, the temperature is raised to 37°C with circulating hot water, and then the temperature in the fermentation tank is reduced to 34°C and then the temperature is raised to 37°C with circulating water, and this cycle is repeated), and the mash is continuously aerated and turned over. The aeration rate is 5 lpm, the aeration and turning time is 20 min, and the rotation speed is 3 rpm; the fermentation is terminated when the alcohol content in the mash is lower than 0.5 g / 100 g and the acetic acid concentration remains unchanged.

[0059] Example 5

[0060] This embodiment provides a method for producing traditional edible vinegar by using a temperature-controlled acetic acid fermentation method. The preparation method is the same as that of Example 4, except that in step (7), in the late fermentation stage, the fermentation is carried out under shaking at 34-36°C (first heated to 36°C with circulating hot water, then heated to 34°C in the fermentation tank and then heated to 36°C with circulating water, and this cycle is repeated), and continuous ventilation and stirring of the mash is performed at an aeration rate of 5 lpm, a ventilation and stirring time of 20 minutes, and a rotation speed of 3 rpm. Under these conditions, fermentation is carried out and tracking sampling is performed, and fermentation is terminated when the alcohol content in the mash is less than 0.5 g / 100 g and the acetic acid concentration remains unchanged.

[0061] Example 6

[0062] This embodiment provides a method for producing traditional vinegar using a temperature-controlled acetic acid fermentation method. The preparation method is the same as that of Example 5, except that in step (7), the aeration rate is 7 lpm in the early, middle, and late fermentation stages.

[0063] Comparative Example 1

[0064] This comparative example provides a method for producing traditional vinegar by solid-state fermentation.

[0065] Steps (1) to (6) are the same as in Example 1.

[0066] (7) Acetic acid fermentation: In the early fermentation stage (0-5 days), the temperature starts at 34°C and rises by 2°C every day, reaching a maximum temperature of 42°C on the 5th day. In the middle fermentation stage (6-10 days), the temperature drops by 2°C every day. In the late fermentation stage (10 days to the end of fermentation), the temperature is kept constant at 34°C. The ventilation and stirring cycle in the early and middle fermentation stages is 8 hours, and in the late fermentation stage, the ventilation and stirring cycle is 4 hours. During the entire acetic acid fermentation period, the ventilation rate is 5 lpm, the ventilation and stirring time is 20 minutes, and the rotation speed is 3 rpm. Fermentation is carried out under these conditions and tracking sampling is carried out. Fermentation is terminated when the alcohol content in the mash is less than 0.5 g / 100 g and the acetic acid concentration remains unchanged.

[0067] Comparative Example 2

[0068] This comparative example provides a method for producing traditional vinegar by solid-state fermentation.

[0069] Steps (1) to (6) are the same as in Example 1.

[0070] (7) Acetic acid fermentation: The entire acetic acid fermentation was carried out at a constant temperature of 34°C. The ventilation and stirring period in the early and middle fermentation stages was 8 hours, and in the late fermentation stage it was 4 hours. During the entire acetic acid fermentation period, the ventilation rate was 5 lpm, the ventilation and stirring time was 20 minutes, and the rotation speed was 3 rpm. Fermentation was carried out under these conditions and follow-up sampling was performed. Fermentation was terminated when the alcohol content in the mash was less than 0.5 g / 100 g and the acetic acid concentration remained unchanged.

[0071] Comparative Example 3

[0072] This comparative example provides a method for producing traditional vinegar by solid-state fermentation.

[0073] Steps (1) to (6) are the same as in Example 1.

[0074] (7) Acetic acid fermentation: The entire acetic acid fermentation was carried out at a constant temperature of 37°C. The ventilation and stirring period in the early and middle fermentation stages was 8 hours, and in the late fermentation stage it was 4 hours. During the entire acetic acid fermentation period, the ventilation rate was 5 lpm, the ventilation and stirring period was 20 minutes, and the rotation speed was 3 rpm. Fermentation was carried out under these conditions and follow-up sampling was performed. Fermentation was terminated when the alcohol content in the mash was less than 0.5 g / 100 g and the acetic acid concentration remained unchanged.

[0075] Comparative Example 4

[0076] This comparative example provides a method for producing traditional vinegar by solid-state fermentation.

[0077] Steps (1) to (6) are the same as in Example 1.

[0078] (7) Acetic acid fermentation: The entire acetic acid fermentation was carried out at a constant temperature of 40°C. The ventilation and stirring period in the early and middle fermentation stages was 8 hours, and in the late fermentation stage it was 4 hours. During the entire acetic acid fermentation period, the ventilation rate was 5 lpm, the ventilation and stirring period was 20 minutes, and the rotation speed was 3 rpm. Fermentation was carried out under these conditions and follow-up sampling was performed. Fermentation was terminated when the alcohol content in the mash was less than 0.5 g / 100 g and the acetic acid concentration remained unchanged.

[0079] Verification Example 1

[0080] After the acetic acid fermentation was completed, the contents of total acid, lactic acid, reducing sugar, amino acids (amino acid nitrogen) and main flavor substances (acetoin) in the vinegar mash samples obtained in Examples 1-6 and Comparative Examples 1-4 were detected, and the raw material utilization rate and fermentation rate were calculated. The results are shown in Tables 1 and 2.

[0081] Table 1 Physical and chemical results of the vinegar mash samples obtained in Comparative Examples 1-4

[0082]

[0083] Table 2 Physical and chemical results of the vinegar-wheat samples obtained in Examples 1-6

[0084]

[0085] As shown in Tables 1 and 2, compared with the fermentation method provided in the comparative example, the staged temperature-varied fermentation method for producing vinegar according to the embodiment achieved significant improvements in key indicators of the vinegar mash: total acid content increased by 5.02%-10.08%, lactic acid content increased by 16.67%-19.53%, significantly improving the taste of the vinegar, reducing the irritation of the vinegar, and mellowing the aftertaste; amino acid nitrogen content increased by 43.48%-83.33%, indicating that the protein decomposition efficiency was improved, which helped to enhance the umami taste of the vinegar and enrich its flavor layer; the content of acetoin, the main flavor substance in the vinegar mash, was significantly increased by 30.30%-138.89%, which not only enhanced the aromatic characteristics of the vinegar, but also enriched the overall flavor complexity of the vinegar. At the same time, the process significantly optimized the fermentation efficiency: the fermentation cycle was shortened by 2-3 days, the raw material utilization rate was increased by 19.78%-24.88%, and the fermentation rate was increased by 30.00%-36.84%.

[0086] In summary, the method provided by the present invention can significantly increase the content of key substances such as acetic acid, lactic acid, reducing sugars and amino acid nitrogen in vinegar, rapidly increase the accumulation of acetoin, improve the ratio of volatile acid to non-volatile acid, make the vinegar odor softer and the aftertaste longer, and improve the flavor of vinegar. This not only improves the flavor quality of vinegar and improves the taste, but also significantly improves production efficiency and economic benefits.

[0087] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A temperature-controlled acetic acid fermentation method, characterized in that: The following steps are involved: S1: mixing wine mash with auxiliary materials to obtain fermentation raw materials; inoculating acetic acid fermentation bacteria into the fermentation raw materials and stirring them evenly to obtain vinegar mash; S2: The vinegar mash undergoes acetic acid fermentation in a solid-state fermentation container: in the early fermentation stage, the fermentation time is 5 days, the vinegar mash is heated to 40°C within 1 hour at the beginning of fermentation, and when the temperature naturally drops to 34°C, the temperature is raised to 40°C within 1 hour, and ventilation and turning are carried out during this period; in the middle fermentation stage, the fermentation time is 5 days, the temperature of the vinegar mash is controlled to be 34-40°C during this period, and when the temperature of the vinegar mash naturally drops to 34°C, the temperature is raised to 40°C within 1 hour, and ventilation and turning are carried out during this period; in the late fermentation stage, the temperature of the vinegar mash is controlled to be 34-40°C during this period, and ventilation and turning are carried out during this period; the fermentation is terminated when the alcohol content in the vinegar mash is lower than 0.5 g / 100 g vinegar mash and the acetic acid concentration remains unchanged.

2. The temperature-controlled acetic acid fermentation method according to claim 1, wherein: During the late fermentation stage in step S2, the temperature of the mash is controlled to be 34-36° C., and when the temperature of the mash naturally drops to 34° C., it is heated to 36° C. within 1 hour.

3. The temperature-controlled acetic acid fermentation method according to claim 1 or 2, wherein: The method of heating in step S2 is to heat the solid-state fermentation container using hot circulating water.

4. The temperature-controlled acetic acid fermentation method according to claim 1, wherein: The ventilation rate of the aeration and turning of the mash during the early fermentation stage, the middle fermentation stage and the late fermentation stage in step S2 is 5-7 lpm.

5. The temperature-controlled acetic acid fermentation method according to claim 4, wherein: The ventilation rate was 5 lpm.

6. The temperature-controlled acetic acid fermentation method according to claim 1, wherein: During the early fermentation stage and the mid-fermentation stage in step S2, ventilation and stirring of the mash are performed every 8-12 hours; the duration of the ventilation and stirring of the mash is 20 minutes.

7. The temperature-controlled acetic acid fermentation method according to claim 6, wherein: In the later fermentation stage described in step S2, ventilation and stirring of the mash are continuously performed.

8. The temperature-controlled acetic acid fermentation method according to claim 6 or 7, wherein: The rotation speed of the ventilation and stirring mash is 3 rpm.

9. Use of the temperature-variable acetic acid fermentation method according to any one of claims 1 to 8 in producing vinegar by solid-state fermentation.

10. Vinegar prepared by the temperature-controlled acetic acid fermentation method according to any one of claims 1 to 8.

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