Vinasse polypeptide and preparation method thereof

Abstract

The invention relates to the field of vinasse polypeptides, aims to solve the problem that existing vinasse polypeptides are difficult to be directly reused in the wine brewing industry, and provides a preparation method of vinasse polypeptides, which comprises the following steps: S100, drying and crushing vinasse, adding deionized water, and hydrolyzing by compound protease to obtain a first enzymatic hydrolysate; s200, filtering the first enzymatic hydrolysate to obtain a first permeate and a first trapped fluid; s300, filtering the first permeate to obtain a second permeate and a second trapped fluid; carrying out secondary enzymolysis to obtain a second enzymatic hydrolysate; s400, filtering the second enzymatic hydrolysate to obtain a third permeate and a third trapped fluid; s500, analyzing and judging the improvement condition of the wine quality in the trapped fluid and the permeate; and S600, obtaining a final enzymolysis process of the vinasse according to the lifting condition, and preparing the vinasse polypeptide through the final enzymolysis process. According to the method, the difference of polypeptide distribution in trapped fluids and permeate liquids is improved by adjusting an enzymolysis process, so that polypeptides capable of improving the quality of finished wine are screened out.

Description

Technical Field

[0001] This invention relates to the field of distillers' grains polypeptides, and more specifically, to a distillers' grains polypeptide and its preparation method. Background Technology

[0002] In the brewing process of baijiu (Chinese liquor), the amount of lees produced for every ton of baijiu is approximately six to ten times the volume of the liquor itself. This lees is rich in various functional components. Currently, the comprehensive utilization of lees mainly focuses on the development of livestock feed, fuel production, and the production of chemical raw materials. However, the economic benefits of developing lees into feed are low, and developing it into fuel faces problems such as secondary pollution. Furthermore, because lees contain various food-derived bioactive substances, existing technologies have also researched the application of lees hydrolysis products. Some studies have even found that bioactive peptides obtained after enzymatic hydrolysis have effects such as lowering blood sugar, improving sleep, and anti-oxidation. However, research on the direct application of lees hydrolysis products in the brewing industry is rarely reported. Summary of the Invention

[0003] The purpose of this invention is to provide a lees polypeptide and its preparation method, thereby solving the problem that existing lees polypeptides are difficult to directly reuse in the brewing industry.

[0004] The embodiments of the present invention are achieved through the following technical solutions: A method for preparing a polypeptide from distiller's grains includes the following steps: S100. After drying and pulverizing the lees, deionized water is added, and then the mixture is hydrolyzed by a complex protease to obtain the first enzymatic hydrolysate. The complex protease includes alkaline protease and neutral protease. The pH of the system is 6-7, the hydrolysis temperature is 30-45℃, and the hydrolysis time is 1-3h. Based on the weight of the lees, the amount of the complex protease added is 4000-6000U / g. S200, the first enzymatic hydrolysate is filtered through a 20-30kDa ultrafiltration membrane to obtain a first permeate and a first retentate; S300, the first permeate is filtered through a 5-10kDa ultrafiltration membrane to obtain the second permeate and the second retentate; Adjust the pH of the first retentate to 9-10, and then perform a second enzymatic hydrolysis at 50-60℃ for 1-2 hours to obtain the second enzymatic hydrolysate; S400, the second enzymatic hydrolysate is filtered through a 5-10kDa ultrafiltration membrane to obtain a third permeate and a third retentate; S500: Analyze and determine the improvement of wine quality by the first retentate, the second retentate, the third retentate, the first permeate, the second permeate, and the third permeate. S600: Based on the improvement, the final enzymatic hydrolysis process of the lees is obtained, and then lees polypeptides are obtained through the final enzymatic hydrolysis process.

[0005] Since distiller's grains are a product of the brewing process, applying them to other fields often involves transportation and sales. However, directly reusing distiller's grains in the brewing process or in alcoholic beverages simplifies the resource utilization process, reduces costs, and further improves product quality. The quality and aroma of baijiu (Chinese white liquor) are influenced by flavor compounds. During brewing, microbial metabolism continuously produces various flavor compounds, some of which are also found in the distiller's grains. Non-volatile substances produced during baijiu brewing, such as acids, sugars, amino acids, and peptides, may interact with volatile substances to regulate the aroma structure of baijiu. Therefore, the applicant hopes to extract polypeptides from the distiller's grains that can be used in baijiu to improve its quality.

[0006] This invention involves multi-stage separation of hydrolysate from distiller's grains and investigates the impact of each stage on the quality of baijiu (Chinese liquor). After obtaining the optimal hydrolysate, the corresponding peptides are enriched through improvements in the enzymatic hydrolysis process, thereby increasing the yield of peptides that can improve baijiu quality. Under the same conditions, different proteases exhibit varying rates of hydrolysis for different protein types. Furthermore, different proteases have different selectivity for their hydrolysate targets. Therefore, using a composite protease for enzymatic hydrolysis not only ensures the effective hydrolysis of the entire protein as much as possible but also increases the difference in the proportion of peptides obtained from different proteases in the hydrolysate, thus increasing the variation in hydrolysate at each stage and making it more beneficial for screening peptides suitable for the brewing industry.

[0007] One of the purposes of using neutral protease and alkaline protease in this invention is to increase the difference in their enzymatic hydrolysis rates by regulating the reaction conditions, thereby increasing the difference in the proportion of their enzymatic hydrolysis products. As a result, the enzymatic hydrolysis products at each stage not only contain as many polypeptide fragments as possible, but also increase the diversity of each polypeptide fragment, which is beneficial for screening polypeptides suitable for the brewing industry.

[0008] The first retentate mainly contains polypeptides with a molecular weight greater than 20-30 kDa obtained by enzymatic hydrolysis under the action of neutral protease; the second retentate mainly contains polypeptides with a molecular weight less than 20-30 kDa and greater than 5-10 kDa obtained by enzymatic hydrolysis under the action of neutral protease; the third retentate mainly contains polypeptides with a molecular weight greater than 5-10 kDa, and the content of polypeptides obtained by enzymatic hydrolysis under the action of alkaline protease is significantly increased; the first permeate mainly contains polypeptides with a molecular weight less than 20-30 kDa obtained by enzymatic hydrolysis under the action of neutral protease; the second permeate mainly contains polypeptides with a molecular weight less than 5-10 kDa obtained by enzymatic hydrolysis under the action of neutral protease; the third permeate mainly contains polypeptides with a molecular weight less than 5-10 kDa, and the content of polypeptides obtained by enzymatic hydrolysis under the action of alkaline protease is significantly increased.

[0009] The quality of wines can be set according to sensory evaluation standards, such as color and appearance, aroma, taste, and style. When screening for peptides, selection can be made according to actual needs, such as assigning different weights to evaluation factors and selecting peptides based on the final score. Alternatively, a single evaluation factor can be selected as the standard, for example, using the aroma score as the standard and selecting the peptide with the highest score.

[0010] Preferably, the mass ratio of the neutral protease to the alkaline protease is 1:(1.5-2).

[0011] In order to broaden the distribution range of peptides in each permeate and retentate, and to ensure that the peptides obtained by alkaline protease hydrolysis have a sufficient amount to affect the quality of the wine, this invention appropriately increases the amount of alkaline protease while ensuring the difference in peptide proportion.

[0012] Preferably, S100 includes: drying and pulverizing the lees to obtain lees powder, obtaining pretreated lees powder through a loosening process, adding deionized water, and then hydrolyzing it with a compound protease to obtain a first enzymatic hydrolysate; The loosening process includes: loading the distiller's grains powder into a high-pressure autoclave, heating it to 120-150℃, raising the steam pressure to 1.5-2MPa, holding the pressure for 5-10 minutes, and then releasing the pressure instantly.

[0013] In the process of extracting polypeptides from distiller's grains, hydrolysis of polysaccharide structures such as cellulose is often required to better release or expose the protein structure and promote the hydrolytic action of proteases. However, the hydrolysis of polysaccharides makes the final polypeptide separation process more complicated. Therefore, the applicant has devised a method that can fully utilize the protease effect without adding cellulase or other enzymes. This method uses high temperature and high pressure, as well as instantaneous pressure relief, to soften and destroy the fibrous structure, making the distiller's grains loose and porous.

[0014] The depressurization time is less than 1 second.

[0015] Preferably, the loosening process includes: after instantaneous depressurization, immersing the distiller's grains powder in 0.3-0.5% acetic acid for 1-2 hours, and finally obtaining pretreated distiller's grains powder after filtration and washing.

[0016] After the lees become loose and porous, the effect of acetic acid is greatly enhanced. It can slightly disrupt the cross-linking structure of polysaccharides and improve enzyme accessibility.

[0017] Weak acids can avoid or reduce their impact on proteins. Washing with water can prevent acids from affecting proteases.

[0018] Preferably, S500 includes: separating polypeptides from the first retentate, the second retentate, the third retentate, the first permeate, the second permeate, and the third permeate through a separation process, adding the polypeptides to the same type of finished wine, and then judging the aroma change of the finished wine. The S600 includes: an enzymatic hydrolysis process corresponding to the retentate or permeate that meets preset conditions based on the aroma changes, to obtain the final enzymatic hydrolysis process of the distiller's grains.

[0019] Since multiple aroma changes may occur in the aforementioned retentate or permeate to meet the preset conditions, it may be necessary to consider multiple corresponding enzymatic hydrolysis processes. Aroma changes can be calculated by subtracting the aroma score of the finished wine without added peptides from the aroma score of the finished wine after adding peptides. A positive difference indicates an enhanced aroma, while a negative difference indicates a weakened aroma.

[0020] Preferably, the amount of polypeptide added in S500 is based on the highest aroma score of the finished wine.

[0021] Due to differences in the types and distribution of polypeptides, their ability to enhance the aroma of finished wine varies. At the same dosage, one polypeptide composition may be less effective than another, but by increasing the dosage, its maximum aroma enhancement may be greater than that of another polypeptide composition. Therefore, this invention uses the highest aroma score in the finished wine as the standard for polypeptide addition. Experiments have shown that the optimal addition amount for each polypeptide composition is 0.05-0.1 g / L.

[0022] Preferably, in step S500, after adding the polypeptide to the same type of finished wine, it is stored for 30-60 days, and then the aroma retention rate is obtained. The aroma change includes: aroma retention rate; the storage conditions are a temperature of 45-60℃ and an ambient illuminance of 500-600lx.

[0023] Peptides can interact with volatile flavor components, thus contributing to aroma retention to a certain extent. Therefore, this invention focuses on investigating the aroma retention rate of the finished liquor after storage when exploring aroma changes.

[0024] The storage method in this invention is not cellar storage, but rather conventional storage for product bottling or sale, with appropriate storage conditions set to accelerate the aging of the finished wine.

[0025] Fragrance retention rate = 100% * (initial aroma score - aroma score after storage) / initial aroma score.

[0026] Preferably, the final enzymatic hydrolysis process includes: B100. After drying and pulverizing the distiller's grains, deionized water is added, followed by the addition of neutral protease for a first enzymatic hydrolysis to obtain a first hydrolysate. Based on the weight of the distiller's grains, the amount of neutral protease added is 2000-4000 U / g, the hydrolysis temperature is 30-35℃, the hydrolysis time is 2-4h, and the pH of the system is 6-7. The first hydrolysate is then filtered sequentially through a 20-30kDa ultrafiltration membrane and a 5-10kDa ultrafiltration membrane to obtain a first retentate corresponding to the 20-30kDa ultrafiltration membrane and a second retentate corresponding to the 5-10kDa ultrafiltration membrane. B200. After adjusting the pH of the primary retentate to 9-10, add alkaline protease for secondary enzymatic hydrolysis to obtain a secondary hydrolysate. The amount of alkaline protease added is 1500-3000 U / g, the hydrolysis temperature is 30-35℃, and the hydrolysis time is 2-4h. The secondary hydrolysate is then filtered through a 5-10kDa ultrafiltration membrane to obtain a secondary permeate. B300: The secondary permeate and secondary retentate are combined to obtain a mixture, which is then separated to obtain distillers' grains polypeptides.

[0027] Experiments showed that both the third permeate and the second retentate had good effects on improving the quality of alcoholic beverages. Therefore, this invention enriched the product based on the composition of the two.

[0028] Preferably, the separation process includes: adding anhydrous ethanol to the mixture, controlling the volume fraction of ethanol in the system to be 50%-70%, then letting it stand at 4-6℃ for 12-24 hours, and then obtaining the precipitate through a centrifugation process. The precipitate is then washed and dried to obtain the distiller's grains polypeptide.

[0029] Centrifugation speed can be 4000-6000 r / min. Drying temperature can be selected from 80-100℃.

[0030] A lees polypeptide prepared by the aforementioned preparation method.

[0031] The present invention has at least the following beneficial effects: This invention improves the diversity of peptide distribution in various retentate and permeate solutions by adjusting the enzymatic hydrolysis process, thereby enabling the screening of peptides suitable for brewing processes or finished wines. During enzymatic hydrolysis, this invention reduces the hydrolysis of polysaccharides such as cellulose, simplifying the separation process and avoiding the influence of polysaccharide components in the retentate or permeate on wine quality, thus improving the accuracy of peptide effect evaluation. It provides new application directions for distiller's grains peptides and corresponding application methods. Reusing distiller's grains peptides in the wine itself reduces recycling costs and facilitates industrial promotion. Detailed Implementation

[0032] To make the objectives, methods, and advantages of the embodiments of the present invention clearer, the methods in the embodiments of the present invention will be clearly and completely described. Obviously, the described embodiments are some embodiments of the present invention, but not all embodiments.

[0033] Example 1: A method for preparing a polypeptide from distiller's grains, comprising the following steps: S100. After drying and pulverizing the lees, lees powder is obtained. The lees powder is then pretreated through a loosening process, deionized water is added, and then hydrolyzed by a complex protease to obtain the first enzymatic hydrolysate. The complex protease includes alkaline protease and neutral protease. The pH of the system is 6-7, the hydrolysis temperature is 30-45℃, and the hydrolysis time is 1-3h. Based on the weight of the lees, the amount of the complex protease added is 4000-6000U / g. The loosening process includes: loading the distiller's grains powder into a high-pressure autoclave, heating it to 120-150℃, raising the steam pressure to 1.5-2MPa, holding the pressure for 5-10 minutes, releasing the pressure instantly, then immersing the distiller's grains powder in 0.3-0.5% acetic acid for 1-2 hours, and finally obtaining pretreated distiller's grains powder after filtration and washing with water. The mass ratio of the neutral protease to the alkaline protease is 1:(1.5-2). S200, the first enzymatic hydrolysate is filtered through a 20-30kDa ultrafiltration membrane to obtain a first permeate and a first retentate; S300, the first permeate is filtered through a 5-10kDa ultrafiltration membrane to obtain the second permeate and the second retentate; Adjust the pH of the first retentate to 9-10, and then perform a second enzymatic hydrolysis at 50-60℃ for 1-2 hours to obtain the second enzymatic hydrolysate; S400, the second enzymatic hydrolysate is filtered through a 5-10kDa ultrafiltration membrane to obtain a third permeate and a third retentate; S500: Analyze and determine the improvement of wine quality by the first retentate, the second retentate, the third retentate, the first permeate, the second permeate, and the third permeate. S600: Based on the improvement, the final enzymatic hydrolysis process of the lees is obtained, and then lees polypeptides are obtained through the final enzymatic hydrolysis process.

[0034] Example 2: When using the aroma change of wine as the screening standard for peptides, an improvement was made based on Example 1. In this example, S500 includes: separating peptides from the first retentate, second retentate, third retentate, first permeate, second permeate, and third permeate through a separation process; adding the peptides to a similar finished wine; storing for 30-60 days; and then obtaining the aroma retention rate. The aroma change includes the aroma retention rate. The storage conditions are a temperature of 45-60℃ and an ambient illuminance of 500-600 lx. The separation process includes: adding anhydrous ethanol to the mixture, controlling the volume fraction of ethanol in the system to be 50%-70%, then letting it stand at 4-6℃ for 12-24 hours, and then obtaining the precipitate through a centrifugation process. The precipitate is then washed and dried to obtain the lees polypeptide.

[0035] The amount of polypeptide added in S500 is based on the highest aroma score of the finished wine. The S600 includes: an enzymatic hydrolysis process corresponding to the retentate or permeate that meets preset conditions based on the aroma changes, to obtain the final enzymatic hydrolysis process of the distiller's grains.

[0036] Example 1: A method for preparing a polypeptide from distiller's grains, comprising the following steps: S100. After drying and pulverizing the lees, lees powder is obtained. The lees powder is then pretreated through a loosening process, deionized water is added, and then hydrolyzed by a complex protease to obtain the first enzymatic hydrolysate. The complex protease includes alkaline protease and neutral protease. The pH of the system is 7, the hydrolysis temperature is 45℃, and the hydrolysis time is 2h. Based on the weight of the lees, the amount of complex protease added is 5000U / g. The loosening process includes: loading the distiller's grains powder into a high-pressure autoclave, heating it to 130°C, raising the steam pressure to 1.8 MPa, maintaining the pressure for 8 minutes, and then releasing the pressure instantly (0.8 s). The distiller's grains powder is then soaked in 0.4 wt% acetic acid for 1-2 hours, and finally filtered and washed with water to obtain pretreated distiller's grains powder. The mass ratio of the neutral protease to the alkaline protease is 1:2; S200. The first enzymatic hydrolysate is filtered through a 30kDa ultrafiltration membrane to obtain a first permeate and a first retentate. S300, the first permeate is filtered through a 5kDa ultrafiltration membrane to obtain the second permeate and the second retentate; The pH of the first retentate was adjusted to 9, and after a second enzymatic hydrolysis at 60°C for 2 hours, the second enzymatic hydrolysate was obtained. S400, the second enzymatic hydrolysate is filtered through a 5kDa ultrafiltration membrane to obtain a third permeate and a third retentate; The S500 process includes: separating polypeptides from the first retentate, the second retentate, the third retentate, the first permeate, the second permeate, and the third permeate through a separation process; adding the polypeptides to a similar finished wine; storing the wine for 45 days; and then obtaining the aroma retention rate. The aroma change includes the aroma retention rate. The storage conditions are a temperature of 50°C and an ambient illuminance of 500 lx. The separation process includes: adding anhydrous ethanol to the mixture, controlling the volume fraction of ethanol in the system to be 60%, then letting it stand at 5°C for 18 hours, and then obtaining the precipitate through a centrifugation process (5000 r / min). The precipitate is then washed and dried to obtain the lees polypeptide.

[0037] The lees used in Experiment Example 1 were Luzhou-style lees, which contain conventional components such as starch, fat, and protein, as well as non-volatile components such as organic acids, reducing sugars, fats, minerals, and vitamins.

[0038] Sensory evaluation was conducted on the finished wine with added polypeptides in Experiment Example 1 and the finished wine after storage. The specific methods are as follows: Fifteen judges were selected to score the wine’s color, aroma and taste. The lowest and highest scores for each evaluation item were removed and the average score was taken. The evaluation criteria are shown in Table 1.

[0039] Table 1

[0040] This experiment only selected aromas for evaluation as an example, and the evaluation results are shown in Table 2.

[0041] Table 2

[0042] As shown in Table 2, the aroma of the finished wine was slightly enhanced after the addition of the second retentate and the third permeate, but the aroma retention rate was significantly higher than that of the finished wine. The aroma of the third retentate, the first permeate, and the second permeate was similar to that of the blank example (finished wine), but the aroma retention rate was not as good.

[0043] Example 3: Based on the above experimental examples, this example provides a method for preparing distillers' grains polypeptide, including: B100. After drying and pulverizing the lees, deionized water is added, followed by the addition of neutral protease for a first enzymatic hydrolysis to obtain a first hydrolysate. Based on the weight of the lees, the amount of neutral protease added is 2000 U / g, the hydrolysis temperature is 30℃, the hydrolysis time is 2h, and the pH of the system is 7. The first hydrolysate is then filtered sequentially through a 30kDa ultrafiltration membrane and a 5kDa ultrafiltration membrane to obtain a first retentate corresponding to the 30kDa ultrafiltration membrane and a second retentate corresponding to the 5kDa ultrafiltration membrane. B200. After adjusting the pH of the primary retentate to 9, alkaline protease is added for secondary enzymatic hydrolysis to obtain a secondary hydrolysate. The amount of alkaline protease added is 2500 U / g, the hydrolysis temperature is 35℃, and the hydrolysis time is 3h. The secondary hydrolysate is filtered through a 5kDa ultrafiltration membrane to obtain a secondary permeate. B300: The secondary permeate and secondary retentate are combined to obtain a mixture, which is then separated to obtain distillers' grains polypeptides.

[0044] The separation process includes: adding anhydrous ethanol to the mixture, controlling the volume fraction of ethanol in the system to be 60%, then letting it stand at 5°C for 18 hours, and then obtaining the precipitate through a centrifugation process (5000 r / min). The precipitate is then washed and dried to obtain the lees polypeptide.

[0045] Example 4: Based on the above experimental examples, this example provides a method for preparing distillers' grains polypeptide, comprising: B100. After drying and pulverizing the lees, deionized water is added, followed by the addition of neutral protease for a first enzymatic hydrolysis to obtain a first hydrolysate. Based on the weight of the lees, the amount of neutral protease added is 4000 U / g, the hydrolysis temperature is 35℃, the hydrolysis time is 4h, and the pH of the system is 6. The first hydrolysate is then filtered sequentially through a 30kDa ultrafiltration membrane and a 5kDa ultrafiltration membrane to obtain a first retentate corresponding to the 30kDa ultrafiltration membrane and a second retentate corresponding to the 5kDa ultrafiltration membrane. B200. After adjusting the pH of the primary retentate to 9, alkaline protease is added for secondary enzymatic hydrolysis to obtain a secondary hydrolysate. The amount of alkaline protease added is 1500 U / g, the hydrolysis temperature is 30℃, and the hydrolysis time is 4h. The secondary hydrolysate is filtered through a 5kDa ultrafiltration membrane to obtain a secondary permeate. B300: The secondary permeate and secondary retentate are combined to obtain a mixture, which is then separated to obtain distillers' grains polypeptides.

[0046] The separation process includes: adding anhydrous ethanol to the mixture, controlling the volume fraction of ethanol in the system to be 50%, then letting it stand at 4°C for 12 hours, and then obtaining the precipitate through a centrifugation process (5000 r / min). The precipitate is washed and dried to obtain the lees polypeptide.

[0047] Example 5: Based on the above experimental examples, this example provides a method for preparing distiller's grains polypeptide, comprising: B100. After drying and pulverizing the distiller's grains, deionized water is added, followed by the addition of neutral protease for a first enzymatic hydrolysis to obtain a first hydrolysate. Based on the weight of the distiller's grains, the amount of neutral protease added is 3000-4000 U / g, the hydrolysis temperature is 30℃, the hydrolysis time is 3h, and the pH of the system is 7. The first hydrolysate is then filtered sequentially through a 30kDa ultrafiltration membrane and a 5kDa ultrafiltration membrane to obtain a first retentate corresponding to the 30kDa ultrafiltration membrane and a second retentate corresponding to the 5kDa ultrafiltration membrane. B200. After adjusting the pH of the primary retentate to 9, alkaline protease is added for secondary enzymatic hydrolysis to obtain a secondary hydrolysate. The amount of alkaline protease added is 3000 U / g, the hydrolysis temperature is 35℃, and the hydrolysis time is 4h. The secondary hydrolysate is filtered through a 5kDa ultrafiltration membrane to obtain a secondary permeate. B300: The secondary permeate and secondary retentate are combined to obtain a mixture, which is then separated to obtain distillers' grains polypeptides.

[0048] The separation process includes: adding anhydrous ethanol to the mixture, controlling the volume fraction of ethanol in the system to 70%, then letting it stand at 6°C for 24 hours, and then obtaining the precipitate through a centrifugation process (5000 r / min). The precipitate is washed and dried to obtain the lees polypeptide.

[0049] The lees polypeptides prepared according to the preparation methods provided in Examples 3-5 were added to the finished wine in equal amounts, with an addition amount of 0.08 g / L. Sensory evaluation was performed on the finished wine before the addition of polypeptides and on the finished wine after storage. The sensory evaluation method is the same as that in Experiment 1. The evaluation results are shown in Table 3.

[0050] Table 3 Before storage After storage (45 days) Fragrance retention rate Example 3 27.14 25.62 94.40% Example 4 27.69 26.03 94.01% Example 5 27.85 25.91 93.03% As can be seen from the evaluation results in Table 3, the aroma retention rate of the finished wine increased significantly after peptide enrichment.

[0051] The above are merely preferred embodiments of the present invention and are not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for preparing a polypeptide from distiller's grains, characterized in that, Includes the following steps: S100. After drying and pulverizing the lees, deionized water is added, and then the mixture is hydrolyzed by a complex protease to obtain the first enzymatic hydrolysate. The complex protease includes alkaline protease and neutral protease. The pH of the system is 6-7, the hydrolysis temperature is 30-45℃, and the hydrolysis time is 1-3h. Based on the weight of the lees, the amount of the complex protease added is 4000-6000U / g. S200, the first enzymatic hydrolysate is filtered through a 20-30kDa ultrafiltration membrane to obtain a first permeate and a first retentate; S300, the first permeate is filtered through a 5-10kDa ultrafiltration membrane to obtain the second permeate and the second retentate; Adjust the pH of the first retentate to 9-10, and then perform a second enzymatic hydrolysis at 50-60℃ for 1-2 hours to obtain the second enzymatic hydrolysate; S400, the second enzymatic hydrolysate is filtered through a 5-10kDa ultrafiltration membrane to obtain a third permeate and a third retentate; S500: Analyze and determine the improvement of wine quality by the first retentate, the second retentate, the third retentate, the first permeate, the second permeate, and the third permeate. S600: Based on the improvement, the final enzymatic hydrolysis process of the lees is obtained, and then lees polypeptides are obtained through the final enzymatic hydrolysis process.

2. The preparation method according to claim 1, characterized in that, The mass ratio of the neutral protease to the alkaline protease is 1:(1.5-2).

3. The preparation method according to claim 1, characterized in that, The S100 includes: drying and pulverizing the lees to obtain lees powder, and then pre-treating the lees powder by a loosening process, adding deionized water, and then hydrolyzing it with a compound protease to obtain a first enzymatic hydrolysate. The loosening process includes: loading the distiller's grains powder into a high-pressure autoclave, heating it to 120-150℃, raising the steam pressure to 1.5-2MPa, holding the pressure for 5-10 minutes, and then releasing the pressure instantly.

4. The preparation method according to claim 1, characterized in that, The loosening process includes: after instantaneous depressurization, immersing the distiller's grains powder in 0.3-0.5% acetic acid for 1-2 hours, and finally obtaining pretreated distiller's grains powder after filtration and washing.

5. The preparation method according to any one of claims 1-4, characterized in that, The S500 process includes: separating polypeptides from the first retentate, the second retentate, the third retentate, the first permeate, the second permeate, and the third permeate through a separation process; adding the polypeptides to a similar finished wine; and then judging the changes in the aroma of the finished wine. The S600 includes: an enzymatic hydrolysis process corresponding to the retentate or permeate that meets preset conditions based on the aroma changes, to obtain the final enzymatic hydrolysis process of the distiller's grains.

6. The preparation method according to claim 5, characterized in that, The amount of polypeptide added in S500 is based on the standard of achieving the highest aroma score in the finished wine.

7. The preparation method according to claim 5, characterized in that, In S500, the polypeptide is added to the same type of finished wine and stored for 30-60 days, and then the aroma retention rate is obtained; the aroma change includes: aroma retention rate; the storage conditions are a temperature of 45-60℃ and an ambient illuminance of 500-600lx.

8. The preparation method according to claim 5, characterized in that, The final enzymatic hydrolysis process includes: B100. After drying and pulverizing the distiller's grains, deionized water is added, followed by the addition of neutral protease for a first enzymatic hydrolysis to obtain a first hydrolysate. Based on the weight of the distiller's grains, the amount of neutral protease added is 2000-4000 U / g, the hydrolysis temperature is 30-35℃, the hydrolysis time is 2-4h, and the pH of the system is 6-7. The first hydrolysate is then filtered sequentially through a 20-30kDa ultrafiltration membrane and a 5-10kDa ultrafiltration membrane to obtain a first retentate corresponding to the 20-30kDa ultrafiltration membrane and a second retentate corresponding to the 5-10kDa ultrafiltration membrane. B200. After adjusting the pH of the primary retentate to 9-10, add alkaline protease for secondary enzymatic hydrolysis to obtain a secondary hydrolysate. The amount of alkaline protease added is 1500-3000 U / g, the hydrolysis temperature is 30-35℃, and the hydrolysis time is 2-4h. The secondary hydrolysate is then filtered through a 5-10kDa ultrafiltration membrane to obtain a secondary permeate. B300: The secondary permeate and secondary retentate are combined to obtain a mixture, which is then separated to obtain distillers' grains polypeptides.

9. The preparation method according to claim 8, characterized in that, The separation process includes: adding anhydrous ethanol to the mixture, controlling the volume fraction of ethanol in the system to be 50%-70%, then letting it stand at 4-6℃ for 12-24 hours, and then obtaining the precipitate through a centrifugation process. The precipitate is then washed and dried to obtain the lees polypeptide.

10. A lees polypeptide prepared by the preparation method according to any one of claims 1-9.

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