Rice wine, method for preparing the same, and rice vinegar prepared using the same

Abstract

This application relates to the field of food fermentation technology, and particularly to a rice wine, its preparation method, and the rice vinegar prepared therefrom. This application uses fermentation mash prepared from rice and yeast, and protease hydrolysate from rice residue as fermentation materials, to prepare rice wine mash through a post-fermentation process at a suitable temperature. The rice wine prepared from this mash has high levels of ammonia nitrogen and β-phenylethanol. The rice vinegar prepared from this rice wine through acetic acid fermentation also has high levels of ammonia nitrogen and β-phenylethanol. The process of this application does not employ a koji-making method, resulting in a simple production process, stable product quality, and meeting the requirements of liquid vinegar fermentation. This process also enables the secondary utilization of rice residue, reduces post-fermentation waste, and lowers environmental pressure.

Description

Technical Field

[0001] This application relates to the field of food fermentation technology, and in particular to a rice wine, its preparation method, and rice vinegar prepared therefrom. Background Technology

[0002] β-Phenylacetyl alcohol is an aromatic alcohol with a pleasant rose aroma. It is found in the flowers and leaves of various fruits and vegetables, or in their extracted essential oils, and is widely used in food, daily chemical products, and even pharmaceuticals. In fermented foods, β-Phenylacetyl alcohol serves as a typical flavor compound, used to measure the flavor quality of fermented products. β-Phenylacetyl alcohol in fermented products mainly originates from the fermentation metabolism of microorganisms, primarily yeast. Yeast synthesizes β-Phenylacetyl alcohol in two ways: the shikimic acid pathway and the Ehrlich pathway. The Ehrlich pathway is more widely studied; it uses L-phenylalanine as a substrate and synthesizes β-Phenylacetyl alcohol through several enzymatic reactions, resulting in a shorter and more controllable synthesis pathway.

[0003] Amino acid nitrogen is an important flavor substance. For example, glycine and proline contribute to sweetness, while glutamic acid and aspartic acid contribute to umami. Seasonings such as monosodium glutamate (MSG) and chicken bouillon are mainly composed of amino acids or their sodium salts to enhance the flavor of dishes. In fermented products, the amino acid nitrogen content can be increased by adding protein-rich raw materials for fermentation, and simultaneously adding proteases directly or indirectly to break down proteins during fermentation, thereby increasing the required amino acid nitrogen content.

[0004] Current vinegar brewing processes mainly include solid-state fermentation and liquid-state fermentation. Compared with solid-state fermentation, liquid-state fermentation has many advantages, such as shorter fermentation cycle, higher productivity, and greater mechanization and automation. However, because current liquid-state fermentation processes primarily rely on pure culture fermentation using brewing yeast and acetic acid bacteria, the fermentation process lacks the rich microbial participation found in solid-state fermentation. These microorganisms are the main contributors to the flavor compounds in vinegar, resulting in lower levels of amino acids, organic acids, and flavor compounds in liquid vinegar, and a less desirable taste and aroma compared to solid-state vinegar. Therefore, improving the levels of ammonia nitrogen, organic acids, and flavor compounds during liquid vinegar fermentation to enhance product quality is a major research direction for future liquid-fermented vinegar production.

[0005] Existing research on enhancing ammonia nitrogen and flavor compounds in rice vinegar mainly falls into two categories:

[0006] One approach involves screening microbial strains to obtain high-yield flavor compounds, thereby increasing the content of flavor compounds in rice vinegar. For example, patent application CN202010104405.5, entitled "A Strain of Brewing Yeast and Its Application," describes the screening of a strain of brewing yeast capable of efficiently synthesizing β-phenylethanol using L-phenylalanine as a substrate while producing only a small amount of ethanol. However, while increasing the β-phenylethanol content in rice wine, it reduces the overall alcohol content, directly impacting the subsequent acidification and fermentation of rice vinegar, and is therefore unsuitable for improving the quality of rice vinegar products. For example, the paper titled "Metabolic Engineering Modification of Saccharomyces cerevisiae for the Production of β-Phenylene Ethanol" published by Zhu Linghuan et al. describes how, through genetic engineering, the expression of heterologous enzymes in the Ehrlich pathway was adjusted to establish a highly efficient synthetic pathway with amino receptor complementation, thereby achieving the goal of efficient conversion of β-phenylethanol and increasing its production. The patent application CN201810461782.7, entitled "A Strains and Methods for Producing β-Phenylene Ethanol," describes how a high-yielding Enterobacterium β-phenylethanol was obtained through screening, and then the β-phenylethanol production was increased through optimized culture methods. Both of these methods achieve the goal of increasing β-phenylethanol production by changing the strains used in fermentation. However, the direct use of genetically modified strains and Enterobacter β-phenylethanol in food fermentation poses certain food safety risks.

[0007] Another method to enhance flavor compounds is to restore the koji-adding process in solid-state vinegar fermentation, thereby improving the flavor of fermented rice vinegar. For example, the paper titled "Research on High-Amino Acid Vinegar Brewing Technology" published by Zhang Chunjie et al. describes how increasing the amount of protein raw materials and introducing multiple compound koji for multi-strain compound fermentation increases the content of protein and protease in the fermentation liquid, thus increasing the ammonia nitrogen content of the fermented vinegar. The patent application CN201910290136.3, entitled "A Method for Increasing the β-Phenylene Ethanol Content in Rice Wine," describes how developing three new koji processes and mixed fermentation yields rice wine with high β-phenylethanol content. Both methods employ koji-making for rice vinegar or rice wine fermentation to increase ammonia nitrogen or β-phenylethanol. However, using koji-making processes leads to a longer production cycle, increases the number of koji-making steps, and raises production costs. Furthermore, the addition of koji causes the rice wine or rice vinegar to darken in color, become more complex in flavor, and lose purity.

[0008] Currently, there is limited research on optimizing and improving the liquid vinegar fermentation process itself to upgrade the quality of rice vinegar. Therefore, developing a rice vinegar fermentation process that can simultaneously increase ammonia nitrogen and β-phenylethanol, based on the traditional liquid rice vinegar fermentation process, is of significant research importance. Summary of the Invention

[0009] Based on this, one or more embodiments of this application provide a rice wine, a method for preparing the same, and rice vinegar prepared therefrom.

[0010] In a first aspect of this application, a method for preparing rice wine is provided, the method comprising the following steps:

[0011] Rice residue, water, and protease are mixed and hydrolyzed to inactivate the enzyme and prepare protease hydrolysate.

[0012] Mix water and rice, liquefy and saccharify them, then use yeast for pre-fermentation to prepare fermented mash;

[0013] The protein hydrolysate and fermentation mash are mixed and then subjected to post-fermentation to prepare rice wine mash; and,

[0014] Collect the clear liquid from the rice wine mash to prepare rice wine;

[0015] The temperature for post-fermentation is 30℃-33℃.

[0016] In some embodiments of this application, the post-fermentation time is 8-12 days.

[0017] In some embodiments of this application, the amount of the protease hydrolysate used is 0.8% to 1.2% of the weight of the rice.

[0018] In some embodiments of this application, the preparation steps of the protease hydrolysate satisfy one or more of the following conditions:

[0019] (1) The rice residue has a moisture content of 35wt%-50wt%, and the ratio of rice residue, water, and protease used is 1g:10g-20g:10000U-50000U; and,

[0020] (2) The hydrolysis temperature is 35℃-45℃ and the hydrolysis time is 20h-40h. During the hydrolysis process, the mixture is stirred once every 3.5h-4.5h for 5min-15min each time, and the stirring speed is 50rpm-100rpm.

[0021] In some embodiments of this application, the preparation step of the fermentation mash satisfies one or more of the following conditions:

[0022] 1) The weight ratio of rice to water is 1:(3-4);

[0023] 2) The amount of yeast used is 0.1‰-0.5‰ of the weight of the rice; and,

[0024] 3) The temperature for pre-fermentation is 26℃-30℃, and the fermentation time is 3-5 days.

[0025] In some embodiments of this application, enzyme inactivation is performed using a physical enzyme inactivation method; optionally, the physical enzyme inactivation method includes: heating the hydrolyzed product to deactivate the protease; further optionally, the heating temperature is 80℃-100℃ and the heating time is 3h-6h.

[0026] In a second aspect of the embodiments of this application, a rice wine is provided, which is prepared by the preparation method described in the first aspect.

[0027] In a third aspect of this application, a method for preparing rice vinegar is provided, the method comprising the following steps:

[0028] Rice wine is prepared using the preparation method described in the first aspect; and,

[0029] Rice wine and acetic acid bacteria are mixed and fermented with acetic acid to prepare rice vinegar.

[0030] In some embodiments of this application, the preparation steps of the rice vinegar satisfy one or more of the following conditions:

[0031] A) The amount of acetic acid bacteria used is 8%-12% of the weight of the rice wine; and,

[0032] B) The temperature for acetic acid fermentation is 32℃-35℃, and the fermentation time is 1-2 days.

[0033] In a fourth aspect of the embodiments of this application, a rice vinegar is provided, which is prepared by the preparation method described in the third aspect.

[0034] Compared to traditional technologies, the beneficial effects of this application include:

[0035] This application uses fermented mash prepared from rice and yeast, along with protease hydrolysate from rice residue, as fermentation materials to prepare rice wine mash through a post-fermentation process at a suitable temperature. The rice wine prepared from this mash has high levels of ammonia nitrogen and β-phenylethanol. Rice vinegar prepared from this rice wine through acetic acid fermentation also has high levels of ammonia nitrogen and β-phenylethanol. The process described in this application does not employ a koji-making method, resulting in a simple production process, stable product quality, and compliance with the requirements of liquid vinegar fermentation. This process also enables the secondary utilization of rice residue, reduces post-fermentation waste, and lowers environmental impact. Attached Figure Description

[0036] To more clearly illustrate the technical solutions in the embodiments of this application and to more completely understand this application and its beneficial effects, the drawings used in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0037] Figure 1 This is a process flow diagram for this application. Detailed Implementation

[0038] The present application will be further described in detail below with reference to the accompanying drawings, embodiments, and examples. It should be understood that these embodiments and examples are for illustrative purposes only and are not intended to limit the scope of the present application. The purpose of providing these embodiments and examples is to enable a more thorough and comprehensive understanding of the disclosure of the present application. It should also be understood that the present application can be implemented in many different forms and is not limited to the embodiments and examples described herein. Those skilled in the art can make various modifications or alterations without departing from the spirit of the present application, and the equivalent forms obtained also fall within the protection scope of the present application. Furthermore, numerous specific details are set forth in the following description to provide a fuller understanding of the present application. It should be understood that the present application can be implemented without one or more of these details.

[0039] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. The terminology used herein in the specification of this application is for descriptive purposes only and is not intended to be limiting of the application.

[0040] the term

[0041] Unless otherwise stated or in case of contradiction, the terms or phrases used herein shall have the following meanings:

[0042] The terms "and / or," "or / and," and "and / or" as used herein include any one of two or more of the related listed items, as well as any and all combinations of the related listed items. These arbitrary and all combinations include any two related listed items, any more related listed items, or a combination of all related listed items. It should be noted that when at least three items are connected by at least two conjunctions selected from "and / or," "or / and," and "and / or," it should be understood that in this application, the technical solution undoubtedly includes technical solutions connected by "logical AND," and also undoubtedly includes technical solutions connected by "logical OR." For example, "A and / or B" includes three parallel solutions: A, B, and A+B. For example, the technical solution of "A, and / or, B, and / or, C, and / or, D" includes any one of A, B, C, and D (that is, a technical solution that is connected by "logical OR"), as well as any and all combinations of A, B, C, and D, that is, combinations of any two or three of A, B, C, and D, and also combinations of all four of A, B, C, and D (that is, a technical solution that is connected by "logical AND").

[0043] In this application, the terms "multiple", "various", "multiple times", "multi-dimensional", etc., unless otherwise specified, refer to a quantity greater than or equal to 2. For example, "one or more" means one or more than or equal to two.

[0044] The terms “combinations of,” “any combination of,” and “any combination of” used in this article include all suitable combinations of any two or more of the listed items.

[0045] In this document, the term "suitable" as used in phrases such as "suitable combination," "suitable method," and "any suitable method" refers to the ability to implement the technical solution of this application, solve the technical problem of this application, and achieve the expected technical effect of this application.

[0046] In this document, terms such as “preferred,” “better,” “more suitable,” and “ideal” are merely used to describe implementation methods or examples that achieve better results, and should be understood not to limit the scope of protection of this application.

[0047] In this application, terms such as "further," "even further," and "particularly" are used to describe purposes and indicate differences in content, but should not be construed as limiting the scope of protection of this application.

[0048] In this application, "optionally," "optionally," and "optional" mean that something is optional, that is, it means that it is selected from either "with" or "without." If there are multiple "optional" entries in a technical solution, unless otherwise specified, and there are no contradictions or mutual constraints, each "optional" entry shall be independent.

[0049] In this application, the terms "first aspect," "second aspect," "third aspect," "fourth aspect," etc., are used for descriptive purposes only and should not be construed as indicating or implying relative importance or quantity, nor should they be construed as implicitly indicating the importance or quantity of the indicated technical features. Moreover, "first," "second," "third," "fourth," etc., serve only as a non-exhaustive enumeration and should be understood not to constitute a closed limitation on quantity.

[0050] In this application, the technical features described in an open-ended manner include both closed technical solutions consisting of the listed features and open technical solutions that include the listed features.

[0051] In this application, numerical intervals (i.e., numerical ranges) are involved. Unless otherwise specified, the selected numerical distributions within the aforementioned numerical intervals are considered continuous and include the two endpoints (i.e., the minimum and maximum values) of the numerical range, as well as every value between these two endpoints. Unless otherwise specified, when a numerical interval refers only to integers within that interval, it includes the two endpoint integers of the numerical range, as well as every integer between the two endpoints. In this document, this is equivalent to directly listing every integer. For example, if t is an integer selected from 1 to 10, it means that t is any integer selected from the group of integers consisting of 1, 2, 3, 4, 5, 6, 7, 8, 9, and 10. Furthermore, when multiple ranges are provided to describe features or characteristics, these ranges can be merged. In other words, unless otherwise specified, the ranges disclosed herein should be understood to include any and all subranges to which they are included.

[0052] Unless otherwise specified, the temperature parameters in this application are permitted to be either constant-temperature treatment or variations within a certain temperature range. It should be understood that the constant-temperature treatment allows temperature fluctuations within the precision range of the instrument control, such as ±5℃, ±4℃, ±3℃, ±2℃, or ±1℃.

[0053] In this application, %(w / w) and wt% both represent weight percentage, %(v / v) refers to volume percentage, and %(w / v) refers to mass-volume percentage.

[0054] First aspect of the embodiments of this application

[0055] This application provides a method for preparing rice wine, the method comprising the following steps:

[0056] Rice residue, water, and protease are mixed and hydrolyzed to inactivate the enzyme and prepare protease hydrolysate.

[0057] Mix water and rice, liquefy and saccharify them, then use yeast for pre-fermentation to prepare fermented mash;

[0058] The protein hydrolysate and fermentation mash are mixed and then subjected to post-fermentation to prepare rice wine mash; and,

[0059] Collect the clear liquid from the rice wine mash to prepare rice wine;

[0060] The temperature for post-fermentation is 30℃-33℃.

[0061] The rice residue in this application refers to the rice residue after fermentation and filtration of other batches of rice wine. It should be understood that during the rice wine preparation process, after preparing the rice wine mash, the mash is filtered, and the resulting clear liquid is rice wine; the resulting filter residue is called rice residue. The rice residue in the following examples of this application may be the rice residue produced according to the method described in Comparative Example 1, but it is understood that this application is not limited to this.

[0062] In some of these examples, the post-fermentation time is 8 to 12 days (e.g., 8, 8.5, 9, 9.5, 10, 10.5, 11, 11.5, 12 days).

[0063] In some of these examples, the amount of the protease hydrolysate used is 0.8% to 1.2% of the weight of the rice (e.g., 0.8%, 0.9%, 1.0%, 1.1%, 1.2%).

[0064] In some of these examples, the preparation steps of the protease hydrolysate satisfy one or more of the following conditions:

[0065] (1) The moisture content of the rice residue is 35wt%-50wt% (e.g., 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50wt%), and the ratio of rice residue, water, and protease is 1g:10g-20g (1, 2, 4, 6, 8, 10, 12, 14, 16, 18, 20g):1000. 0U-50000U (10000, 12000, 14000, 16000, 18000, 20000, 22000, 24000, 26000, 28000, 30000, 32000, 34000, 36000, 38000, 40000, 42000, 44000, 46000, 48000, 50000U); and,

[0066] (2) The hydrolysis temperature is 35℃-45℃ (e.g., 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45℃), and the hydrolysis time is 20h-40h (e.g., 20, 22, 24, 26, 28, 30, 32, 34, 36, 38, 40h). During the hydrolysis process, the mixture is stirred once every 3.5h-4.5h (e.g., 3.5, 3.6, 3.7, 3.8, 3.9, 4.0, 4.1, 4.2, 4.3, 4.4, 4.5h), for 5min-15min each time (e.g., 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15min), and the stirring speed is 50rpm-100rpm (e.g., 50, 60, 70, 80, 90, 100rpm).

[0067] In some of these examples, the preparation steps of the fermentation mash satisfy one or more of the following conditions:

[0068] 1) The weight ratio of rice to water is 1:(3-4) (e.g., 1:3, 1:3.1, 1:3.2, 1:3.3, 1:3.4, 1:3.5, 1:3.6, 1:3.7, 1:3.8, 1:3.9, 1:4).

[0069] 2) The amount of yeast used is 0.1‰-0.5‰ of the weight of the rice (e.g., 0.1‰, 0.2‰, 0.3‰, 0.4‰, 0.5‰); and,

[0070] 3) The temperature for pre-fermentation is 26℃-30℃ (e.g., 26, 27, 28, 29, 30℃), and the time for pre-fermentation is 3-5 days (e.g., 3, 3.2, 3.4, 3.6, 3.8, 4, 4.2, 4.4, 4.6, 4.8, 5 days).

[0071] In some examples, enzyme inactivation is performed using physical enzyme inactivation methods; optionally, the physical enzyme inactivation method includes: heating the hydrolysis product to deactivate the protease; further optionally, the heating temperature is 80℃-100℃ (e.g., 80, 82, 84, 86, 88, 90, 92, 94, 96, 98, 100℃), and the heating time is 3h-6h (e.g., 3, 3.2, 3.4, 3.6, 3.8, 4, 4.2, 4.4, 4.6, 4.8, 5, 5.2, 5.4, 5.6, 5.8, 6h).

[0072] Second aspect of the embodiments of this application

[0073] This application provides a rice wine prepared by the preparation method described in the first aspect.

[0074] Third aspect of the embodiments of this application

[0075] This application provides a method for preparing rice vinegar, the method comprising the following steps:

[0076] Rice wine is prepared using the preparation method described in the first aspect; and,

[0077] Rice wine and acetic acid bacteria are mixed and fermented with acetic acid to prepare rice vinegar.

[0078] In some embodiments of this application, the preparation steps of the rice vinegar satisfy one or more of the following conditions:

[0079] A) The amount of acetic acid bacteria used is 8%-12% of the weight of the rice wine (e.g., 8%, 9%, 10%, 11%, 12%); and,

[0080] B) The temperature for acetic acid fermentation is 32℃-35℃ (e.g., 32, 33, 34, 35℃), and the fermentation time is 1-2 days (e.g., 1, 1.1, 1.2, 1.3, 1.4, 1.5, 1.6, 1.7, 1.8, 1.9, 2 days).

[0081] Fourth aspect of the embodiments of this application

[0082] This application provides a rice vinegar prepared by the preparation method described in the third aspect.

[0083] The embodiments of this application will be described in detail below with reference to examples. It should be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of this application. For experimental methods in the following embodiments where specific conditions are not specified, please refer to the guidelines given in this application, or follow experimental manuals or conventional conditions in the art, or follow the conditions recommended by the manufacturer, or refer to experimental methods known in the art.

[0084] In the specific embodiments described below, the measurement parameters involving raw material components may have slight deviations within the weighing accuracy range unless otherwise specified. Temperature and time parameters are subject to acceptable deviations due to instrument testing accuracy or operational precision.

[0085] In the following specific examples: Protease: Novozymes' acidic protease, with an optimal reaction temperature of 40°C and an optimal pH of 4-6; Yeast powder: Angel Yeast; Acetic acid bacteria: Taist Biotechnology's acetic acid bacteria. The rice residue is derived from the rice residue after fermentation and filtration of the previous batch of rice wine, and the moisture content of the rice residue is required to be 35%-50%.

[0086] Example 1

[0087] Step 1: Crush the filtered rice residue (moisture content 35wt%-50wt%) into particles no larger than broad beans, specifically with a particle diameter no more than 1cm and a thickness no more than 5mm; add process water at 10 times the weight of the rice residue; add protease powder at a ratio of 40000U / g based on the weight of the rice residue to prepare an enzymatic hydrolysis mixture.

[0088] Step 2: Heat the enzymatically hydrolyzed mixture from Step 1 to 40℃ for 24 hours to hydrolyze the rice residue. Stir for 10 minutes every 4 hours at a speed of 50 rpm. After the treatment is completed, heat-treat at 90℃ for 4 hours and filter to obtain the protease hydrolysate.

[0089] Step 3: Complete the production of rice wine fermentation mash according to the normal liquefaction and saccharification fermentation process, in which the weight ratio of rice to water is 1:3.5.

[0090] Step 4: After liquefaction, saccharification and cooling are completed, add yeast powder at 0.1‰ of the weight of rice in Step 3 for pre-fermentation at 28℃ for 3 days to prepare fermented mash.

[0091] Step 5: Add the protease hydrolysate from Step 2 to the fermentation mash from Step 4 at 1% of the weight of the rice in Step 3, and adjust the fermentation temperature to 32℃ for post-fermentation of rice wine. Ferment for 9 days to prepare rice wine mash. Filter the rice wine mash to obtain clear rice wine liquid (rice wine).

[0092] Step 6: Inoculate with acetic acid bacteria at a ratio of 10% of the weight of the clear liquid, and carry out acidification fermentation to obtain fermented rice vinegar. The fermentation temperature is 32℃ and the fermentation time is 2 days.

[0093] Example 2

[0094] Step 1: Crush the filtered rice residue (moisture content 35wt%-50wt%) into particles no larger than broad beans, specifically with a particle diameter no more than 1cm and a thickness no more than 5mm; add process water at 20 times the weight of the rice residue; add protease powder at a ratio of 10000U / g based on the weight of the rice residue to prepare an enzymatic hydrolysis mixture.

[0095] Step 2: Heat the enzymatically hydrolyzed mixture from Step 1 to 40℃ for 36 hours to hydrolyze the rice residue. Stir for 10 minutes every 4 hours at a speed of 50 rpm. After the treatment is completed, heat-treat at 90℃ for 6 hours and filter to obtain the protein hydrolysate.

[0096] Step 3: Complete the production of rice wine fermentation mash according to the normal liquefaction and saccharification fermentation process, in which the rice-to-water ratio is 1:3.

[0097] Step 4: After liquefaction, saccharification and cooling are completed, add yeast powder at 0.4‰ of the rice weight in Step 3 for pre-fermentation at 26℃ for 5 days to prepare fermented mash.

[0098] Step 5: Add the protease hydrolysate from Step 2 to the fermentation mash from Step 4 at 1.2% of the rice amount from Step 3, and adjust the fermentation temperature to 30℃ for post-fermentation of rice wine for 12 days. Prepare rice wine mash. Filter the rice wine mash to obtain clear rice wine liquid (rice wine).

[0099] Step 6: Inoculate with acetic acid bacteria at a ratio of 10% of the clear liquid volume to carry out acidification fermentation and obtain fermented rice vinegar. The fermentation temperature is 35℃ and the fermentation time is 1 day.

[0100] Comparative Example 1

[0101] This comparative example is a comparative example of Example 1. The difference from Example 1 includes that no protein hydrolysate was prepared for rice wine fermentation. Specifically, the steps include the following:

[0102] Step 3: Complete the production of rice wine fermentation mash according to the normal liquefaction and saccharification fermentation process, wherein the weight ratio of rice to water is 1:3.5.

[0103] Step 4: After liquefaction, saccharification and cooling are completed, add yeast powder at 0.1‰ of the weight of rice in Step 3 for pre-fermentation at 28℃ for 3 days to prepare fermented mash.

[0104] Step 5: Adjust the fermentation temperature of the fermentation mash from Step 4 to 32℃ and carry out post-fermentation of rice wine for 9 days to prepare rice wine mash.

[0105] Step 6: Filter the rice wine mash from Step 5 to obtain clear rice wine liquid and prepare rice wine; inoculate acetic acid bacteria at a ratio of 10% of the weight of the clear liquid for acidification fermentation to obtain fermented rice vinegar. The fermentation temperature is 32℃ and the fermentation time is 2 days.

[0106] Comparative Example 2

[0107] This comparative example is a comparative example of Example 1. The difference from Example 1 includes that protein hydrolysate was not prepared for rice wine fermentation, but protease was added directly during rice wine fermentation. Specifically, the steps include the following:

[0108] Step 3: Complete the production of rice wine fermentation mash according to the normal liquefaction and saccharification fermentation process, in which the weight ratio of rice to water is 1:3.5.

[0109] Step 4: After liquefaction, saccharification and cooling are completed, add yeast powder at 0.1‰ of the weight of rice in Step 3 for pre-fermentation at 28℃ for 3 days to prepare fermented mash.

[0110] Step 5: Add protease at a dosage of 1000 U / g to the fermentation mash from Step 4, based on the weight of the rice in Step 3. Adjust the fermentation temperature to 32℃ and carry out post-fermentation of rice wine for 9 days to prepare rice wine mash. Filter the rice wine mash to obtain clear rice wine liquid.

[0111] Step 6: Inoculate with acetic acid bacteria at a ratio of 10% of the weight of the clear liquid, and carry out acidification fermentation to obtain fermented rice vinegar. The fermentation temperature is 32℃ and the fermentation time is 2 days.

[0112] Comparative Example 3

[0113] This comparative example is a comparative example of Example 1. The difference from Example 1 is that the amino acid mixed hydrolysate in step 2 was not subjected to enzyme inactivation treatment and was directly added to the fermentation mash in step 4.

[0114] Comparative Example 4

[0115] This comparative example is a comparative example of Example 1. The main difference from Example 1 is the addition of an amino acid mixed hydrolysate during the pre-fermentation stage. Specifically, it includes the following steps:

[0116] Step 1: Crush the filtered rice residue into pieces no larger than broad beans; add process water at 10 times the weight of the rice residue; add protease powder at a ratio of 40,000 U / g based on the weight of the rice residue to prepare an enzymatic hydrolysis mixture.

[0117] Step 2: Heat the enzymatically hydrolyzed mixture from Step 1 to 40℃ for 24 hours to hydrolyze the rice residue. Stir for 10 minutes every 4 hours at a speed of 50 rpm. After the treatment is complete, bathe in a 90℃ water bath for 4 hours and filter to obtain the protease hydrolysate.

[0118] Step 3: Complete the production of rice wine fermentation mash according to the normal liquefaction and saccharification fermentation process, in which the weight ratio of rice to water is 1:3.5.

[0119] Step 4: Add the protease hydrolysate from Step 2 to the rice wine fermentation mash at 1% of the rice weight, and add yeast powder at 0.1‰ of the rice weight. Perform pre-fermentation at 28℃ for 3 days.

[0120] Step 5: After the initial fermentation is complete, adjust the fermentation temperature to 32℃ and carry out the secondary fermentation for 9 days. Press and filter the rice wine mash to obtain clear rice wine liquid.

[0121] Step 6: Inoculate with acetic acid bacteria at a ratio of 10% of the weight of the clear liquid, and carry out acidification fermentation to obtain fermented rice vinegar. The fermentation temperature is 32℃ and the fermentation time is 2 days.

[0122] Comparative Example 5

[0123] This comparative example is a comparative example of Example 1. The main difference from Example 1 is that the post-fermentation temperature is 28°C. Specifically, it includes the following steps:

[0124] Step 1: Crush the filtered rice residue into pieces no larger than broad beans; add process water at 10 times the weight of the rice residue; add protease powder at a ratio of 40,000 U / g based on the weight of the rice residue to prepare an enzymatic hydrolysis mixture.

[0125] Step 2: Heat the enzymatically hydrolyzed mixture from Step 1 to 40℃ for 24 hours to hydrolyze the rice residue. Stir for 10 minutes every 4 hours at a speed of 50 rpm. After the treatment is completed, heat-treat at 90℃ for 4 hours and filter to obtain the protease hydrolysate.

[0126] Step 3: Complete the production of rice wine fermentation mash according to the normal liquefaction and saccharification fermentation process, in which the weight ratio of rice to water is 1:3.5.

[0127] Step 4: After liquefaction, saccharification and cooling are completed, add yeast powder at 0.1‰ of the weight of rice in Step 3 for pre-fermentation at 28℃ for 3 days to prepare fermented mash.

[0128] Step 5: Add protease hydrolysate to the fermentation mash after the rice wine pre-fermentation is completed, according to the proportion of 1% of the rice weight in Step 3, continue fermentation at 28℃ for 9 days, press and filter the rice wine mash to obtain clear rice wine liquid.

[0129] Step 6: Inoculate with acetic acid bacteria at a ratio of 10% of the weight of the clear liquid, and carry out acidification fermentation to obtain fermented rice vinegar. The fermentation temperature is 32℃ and the fermentation time is 2 days.

[0130] The β-phenylethanol, alcohol content, total acid, and ammonia nitrogen in the fermented rice wine and rice vinegar of each group of examples were tested. The results are shown in the table below. The testing criteria are as follows:

[0131] β-Phenylephethanol: T / CBJ 8101-2019 Determination of β-Phenylephethanol in Grain-Flavored Cooking Wine by Gas Chromatography.

[0132] Alcohol content: GB5009.225-2023 National Food Safety Standard - Determination of ethanol concentration in wine and edible alcohol.

[0133] Total acidity: GB12456-2021 National Food Safety Standard - Determination of total acidity in food.

[0134] Total nitrogen: GB5009.235-2016 National Food Safety Standard - Determination of amino acid nitrogen in food.

[0135] Table 1

[0136]

[0137] Analysis of the results from each example group shows that, using Example 3 as a blank control group, the ammonia nitrogen and β-phenylethanol levels in Examples 1 and 2 were significantly higher than those in the control group. The levels in Examples 1 and 2 were generally similar, with no significant difference. However, in the remaining groups, some showed high ammonia nitrogen and low β-phenylethanol, or both were low, which did not meet the expected results. Therefore, the schemes in Examples 1 and 2 were the best and met the actual needs.

[0138] In this embodiment, by adding protease hydrolysate from rice residue, the amino acid content is increased in the early stage of fermentation, and the ammonia nitrogen index in the fermented rice vinegar can reach about 0.6 g / L or above. By adjusting the fermentation temperature, the β-phenylethanol index in the fermented rice vinegar can reach more than 145 mg / L, which significantly increases the content of ammonia nitrogen and β-phenylethanol in rice wine and rice vinegar, thereby improving the flavor of rice vinegar and enhancing the product value of rice vinegar.

[0139] The technical features of the above-described embodiments and examples can be combined in any suitable manner. For the sake of brevity, not all possible combinations of the technical features in the above-described embodiments and examples are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0140] The embodiments described above are merely illustrative of several implementation methods of this application, intended to facilitate a detailed understanding of the technical solutions of this application, but should not be construed as limiting the scope of protection of the patent application. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of this application, and these all fall within the scope of protection of this application. Furthermore, it should be understood that after reading the above teachings of this application, those skilled in the art can make various alterations or modifications to this application, and the equivalent forms obtained also fall within the scope of protection of this application. It should also be understood that technical solutions obtained by those skilled in the art based on the technical solutions provided in this application through logical analysis, reasoning, or limited experimentation are all within the scope of protection of the appended claims. Therefore, the scope of protection of this patent application should be determined by the content of the appended claims, and the specification and drawings can be used to interpret the content of the claims.

Claims

1. A method for preparing rice wine that simultaneously increases the content of β-phenylethanol and ammonia nitrogen, characterized in that, The preparation method includes the following steps: Rice residue, water, and protease are mixed and hydrolyzed to inactivate the enzyme and prepare protease hydrolysate. Mix water and rice, liquefy and saccharify them, and then use yeast for pre-fermentation to prepare fermented mash; The protease hydrolysate and fermentation mash are mixed for post-fermentation to prepare rice wine mash; and, Collect the clear liquid from the rice wine mash to prepare rice wine; in, The temperature for secondary fermentation is 30℃-33℃; The post-fermentation time is 8-12 days; The amount of the protease hydrolysate used is 0.8%-1.2% of the weight of the rice; The preparation steps of the protease hydrolysate meet the following conditions: the water content of the rice residue is 35wt%-50wt%, 10g-20g of water and 10000U-50000U of protease are added per 1g of rice residue; the protease is Novozymes' acidic protease; the hydrolysis temperature is 35℃-45℃, and the hydrolysis time is 20h-40h. The preparation steps of the fermented mash meet the following conditions: the amount of yeast used is 0.1‰-0.5‰ of the weight of the rice.

2. The method for preparing rice wine with simultaneously increased β-phenylethanol and ammonia nitrogen content according to claim 1, characterized in that, The preparation steps of the protease hydrolysate satisfy the following conditions: During the hydrolysis process, the mixture is stirred once every 3.5-4.5 hours for 5-15 minutes each time, at a speed of 50-100 rpm.

3. The method for preparing rice wine with simultaneously increased β-phenylethanol and ammonia nitrogen content according to any one of claims 1 to 2, characterized in that, The preparation steps of the fermentation mash satisfy one or more of the following conditions: The weight ratio of rice to water is 1:(3-4); and, The temperature for pre-fermentation is 26℃-30℃, and the fermentation time is 3-5 days.

4. The method for preparing rice wine with simultaneously increased β-phenylethanol and ammonia nitrogen content according to any one of claims 1 to 2, characterized in that, Enzyme inactivation is performed using physical methods.

5. The method for preparing rice wine with simultaneously increased β-phenylethanol and ammonia nitrogen content according to claim 4, characterized in that, The physical enzyme inactivation method includes: heating the hydrolyzed product to deactivate the protease.

6. The method for preparing rice wine with simultaneously increased β-phenylethanol and ammonia nitrogen content according to claim 5, characterized in that, The heat treatment temperature is 80℃-100℃, and the heat treatment time is 3h-6h.

7. A method for preparing rice vinegar, characterized in that, The preparation method includes the following steps: Rice wine is prepared by the preparation method according to any one of claims 1 to 6; and, Rice wine and acetic acid bacteria are mixed and fermented with acetic acid to prepare rice vinegar.

8. The method for preparing rice vinegar according to claim 7, characterized in that, The preparation steps of the rice vinegar satisfy one or more of the following conditions: A) The amount of acetic acid bacteria used is 8%-12% of the weight of the rice wine; and, B) The temperature for acetic acid fermentation is 32℃-35℃, and the fermentation time is 1-2 days.

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