A method for preparing sake using brown rice as a raw material

Abstract

The present application provides a method for preparing Japanese sake by using brown rice as raw material. The method is as follows: using common brown rice, soaking, steaming, then adding sweet koji into saccharification tank, sealing, incubating at 24-28 DEG C, then adjusting workshop temperature to above 6 DEG C and below 10 DEG C to inhibit yeast activity, meanwhile, keeping part of saccharifying mold activity to complete the decomposition and liquefaction of rice starch and saccharification, then squeezing or adding water to bring the lees to carry out the first fermentation, separating the solid rice skin layer rich in protein and fat, pumping the clear liquid into fermentation tank to carry out the second fermentation, sterilizing, clarifying and filtering to obtain Japanese sake. The method of the present application uses brown rice as raw material, without the outer polishing process, can prepare Japanese sake with pure taste, clear body, total acid, amino acid nitrogen and various sensory indexes meeting the Japanese sake brewing style, and the overall raw material and production cost can be reduced by more than 50% compared with the existing Japanese sake production process.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of fermentation brewing, and specifically provides a method for preparing sake with brown rice as raw material. The method realizes the targeted and orderly decomposition of different components of rice by microorganisms through the control of microbial fermentation, and the fermented brown rice is brewed into sake with the quality of the style of brewing and large brewing. BACKGROUND

[0002] Sake is the national liquor of Japan, with an alcohol content of 14%-17%(V), and has the characteristics of soft taste, delicate, sweet taste, and refreshing. The existing Japanese sake is made of polished rice with low protein and fat content as raw material, rice koji or enzyme preparation as saccharifying agent, and is made by fermentation, pressing and sterilization. In the preparation process of sake, protein and minerals are the source of off-flavor of sake. The lower the protein and fat content in the rice raw material, the more delicate the taste of the prepared sake. Therefore, the selection of raw material rice for sake is very demanding. Not only is it required to have low protein and fat content, but also it needs to select rice with starch concentrated in the core of the rice, so that the outer part with high protein and fat content can be easily ground off, and only the core part with high starch content is left for brewing. In general, the fat, protein and starch in ordinary rice are mixed and distributed evenly, and it is difficult to separate protein, fat and starch, so the selection range of raw materials is greatly reduced and the cost of raw materials is increased.

[0003] In the production of Japanese sake, the polished rice rate of the raw material is generally controlled at 10%-75%(Note: 10%-75% refers to the yield of rice excluding husks. The smaller the value, the higher the polished rice rate. 100% is early rice). The polished rice rate of most sake raw materials is about 75%, that is, about 25% of the outer part is removed. Among them, the polished rice rate of pure rice brewing is controlled below 60%, and the polished rice rate of pure rice large brewing is controlled below 50%. In contrast, the polished rice rate of the rice we eat in our daily life is between 90-92%, that is, only 8-10% of the rice bran is removed. In sake brewing, the higher the polished rice rate, the more mellow and rich the rice aroma in the wine. The lower the polished rice rate, the more floral and fruity the wine aroma, and the more delicate the taste. In order to reduce the polished rice rate, more surface layer needs to be ground off, and the protein and fat content of the ground rice core is lower. Only in this way, the aroma and taste of sake can be more pure, refreshing, and can better reflect the true taste of rice. However, the grinding of rice raw materials will result in the consumption of more rice for the production of the same amount of sake, greatly increasing the cost of raw materials. Moreover, the outer layer of rice contains not only protein and fat, but also part of starch. Grinding off the outer layer will result in a large amount of raw material loss and reduce the yield of wine. In conventional sake preparation, the highest yield of 1 ton of brown rice is 1.5 tons of sake. In addition, the grinding of polished rice increases the brewing process and requires separate rice polishing equipment and staff, thereby increasing the production cost.

[0004] Sweet koji is a saccharification bacteria and yeast preparation, which contains microorganisms mainly including rhizopus, mucor and a small amount of yeast. In the fermentation process, saccharification bacteria first decomposes starch in rice into glucose and protein into amino acid, and then a small amount of yeast converts glucose into alcohol through glycolysis. Sweet koji can also be used to brew sake, but since sweet koji contains yeast in addition to saccharification bacteria, it is easy to cause simultaneous saccharification and fermentation during the brewing process. Therefore, the requirement for raw materials is higher when sweet koji is used to brew sake. Chinese rice wine is actually derived from the same source as Japanese sake. Chinese rice wine uses whole rice or waxy rice without polishing, and the saccharification and fermentation are carried out simultaneously during the brewing process. Therefore, a large amount of protein and fat on the surface of rice is hydrolyzed in the wine, resulting in complex and rich taste and mouthfeel. SUMMARY

[0005] The present application provides a method for preparing sake using brown rice as raw material, which can realize the targeted and orderly decomposition of different components of rice by microorganisms through the control of microbial activity, and can brew sake with the flavor of brewing or large brewing using ordinary brown rice without polishing, thereby greatly improving the yield of sake and reducing the production cost of sake.

[0006] To solve the above technical problems, the present application provides a method for preparing sake using brown rice as raw material, which is characterized by the following specific steps:

[0007] (1) Using brown rice as raw material, washing it until the water is clear, then soaking it in water for 4-8 hours;

[0008] (2) After the rice soaked in step (1) is drained, it is steamed and then sprinkled with cold water to 22-28℃. Then, according to the proportion of 0.3%-0.5% of the dry rice weight, sweet koji is added and then the rice is placed in a saccharification tank, the rice is flattened and a wine nest is left in the middle. After sealing, it is placed in a temperature-controlled incubation room at 24-28℃ for 20-28h to activate the saccharification mold;

[0009] (3) The rice with activated saccharification mold in step (2) is transferred to a constant-temperature saccharification room, and the temperature of the saccharification room is set to be greater than 6℃ and less than 10℃. Under this temperature condition, the saccharification mold in the sweet koji decomposes starch into sugar liquid, and the yeast and other bacteria are in a dormant state at low temperature. The cover is opened for aerobic saccharification under low temperature condition, and the saccharification time is greater than 3 days and less than 5 days. The surface of the rice is kept moist by the sugar liquid in the wine nest during the saccharification process;

[0010] (4) The rice with saccharification in step (3) is directly pressed to separate the rice skin layer containing protein and fat, and then the liquid after pressing is adjusted to a sugar content of 25%-35% by adding water and then placed at room temperature for 10-15 days to obtain a sake raw liquid.

[0011] or the rice in step (3) is added with water in a ratio of 1:0.5-2 of dry rice weight, sealed for the first fermentation, the fermentation temperature is 18-22 DEG C, the time is 1-7 days, then the rice skin layer containing protein and fat is separated by pressing the liquid after the first fermentation, and the clear liquid is transferred into a fermentation tank, and placed at room temperature for secondary fermentation for 10-15 days to obtain the raw sake liquid;

[0012] (5) the raw sake liquid obtained after fermentation in step (4) is pasteurized at 62-65 DEG C, incubated for 28-32 min, then quickly cooled to below 30 DEG C, and placed for clarification for 3-7 days, filtered, to obtain Japanese sake with clear wine body and pure and refreshing taste;

[0013] (6) the prepared Japanese sake in step (5) is transferred into a wine storage tank for aging for 10-15 days, and then can be blended and canned for delivery.

[0014] The preferred technical scheme of the present application is that in step (3), the sugar solution in the wine nest is taken out every 1-4 hours and uniformly sprayed onto the surface of the rice, and the rice is kept moist and placed.

[0015] The preferred technical scheme of the present application is that in step (3), the rice is detected for starch residual rate during the saccharification process, and when the starch residual rate is lower than 5%, the saccharification is considered to be completed.

[0016] The preferred technical scheme of the present application is that in step (5), a precipitant is added in an amount of 200-800 g per ton of raw sake liquid during the sterilization process or after the sterilization is completed, and the precipitant is diluted with water and then added into the raw sake liquid; when the precipitant is added during the sterilization process, the precipitant is bentonite, and the weight ratio of bentonite to pure water is 1:10; when the precipitant is added after the sterilization is completed, the precipitant is selected from gelatin, chitosan, fish glue or egg white powder; the weight ratio of gelatin or chitosan to pure water is 1:15-20.

[0017] The present applicant has found through years of research that when the experimental rice fermentation wine is biologically reacted at different temperature intervals, the biological activities of different microorganisms in the koji are different at different temperatures, among which the yeast completely loses activity below 10 DEG C, and the saccharifying mold (Rhizopus, Aspergillus oryzae) still maintains partial activity of decomposing starch into sugar, and stops decomposing starch below 6 DEG C. Therefore, the different designations of the two types of microorganisms (saccharifying mold and yeast) in the koji entering the low-temperature dormancy critical point are named as "microbial activity low-temperature critical value difference".

[0018] The present application uses ordinary brown rice as raw material, without removing the outer layer by grinding, after cleaning, soaking and steaming, sweet koji is added, and then saccharifying mold is activated, and then low-temperature fermentation is inhibited below 10℃, and saccharifying mold can decompose starch to convert into sugar solution above 6℃, and the protein and fat in the outer layer of rice will not be decomposed in this temperature range, and will be attached to the outer layer of rice in solid state, and can be easily separated by later pressing process; after saccharification, the rice can be directly pressed and then fermented at room temperature to brew sake, or water is added to the rice with the bran for the first fermentation for 1-7 days, and then the rice is pressed after the yeast decomposes the protein and other components in the outer layer of rice, and then the pressed liquid is fermented at room temperature for the second time, and then sterilized and clarified to obtain high-quality Japanese sake, and the residue fermentation can improve the taste of the sake, and the decomposition degree of the yeast on the protein and other components in the outer layer of rice can be freely controlled, and Japanese sake of various qualities or styles from pure rice wine to large-scale brewing can be brewed. Because a certain type of microorganism in the koji can be controlled separately, the saccharifying mold can be allowed to decompose starch to convert into sugar before brewing, and the decomposition degree of the yeast on the protein or other components of the raw material can be controlled after saccharification, so even if ordinary brown rice is used without grinding (polishing), Japanese sake of large-scale brewing quality can be brewed.

[0019] The beneficial effects of the present application are:

[0020] (1) The raw material used in the present application can be ordinary brown rice or rice specially used for brewing sake, without grinding (polishing), and can be directly used for steaming and fermentation, and the starch contained in the rice is not wasted, and the utilization rate of raw materials is higher, and the cost of raw materials and pretreatment is greatly reduced.

[0021] (2) The polishing process is reduced in the brewing process of the present application, and the sake brewing process is reduced, and the production workshop, equipment and personnel for polishing can be omitted, and the production and labor costs are greatly reduced, and the production efficiency is improved, and the production capacity can be increased by 5-10 times in the same brewing production workshop area.

[0022] (3) In the brewing process of the present application, only the saccharification temperature and the fermentation temperature in the later stage need to be controlled, and the process production operation is simpler and standardized, and the labor cost can be reduced by more than 50% for the same output.

[0023] (4) The decomposition degree of the yeast on the protein and other components in the outer layer of rice can be freely controlled by adjusting the water addition ratio and the time of fermentation with bran in the present application, and Japanese sake of various qualities or styles from pure rice wine to large-scale brewing can be brewed. DETAILED DESCRIPTION

[0024] The present application will be further described below in conjunction with examples.

[0025] A method for preparing Japanese sake is provided in Example 1, which is characterized by the following specific steps:

[0026] (1) 100 kg of ordinary rice is washed clean until the water is clear, soaked in 300 kg of water for 6 hours, then drained and loaded into a rice steaming cart, steamed to maturity, and then cooled to 22-28°C by pouring with cold water;

[0027] (2) The cooled and drained rice from step (1) is poured into a koji mixing table, lightly shaken to disperse the rice without clumping, 500 g of sweet koji is mixed in, then loaded into a stainless steel mashing tank with dimensions of 120 cm in length, 60 cm in width, and 60 cm in height; two wine pits are dug in the middle of the rice to facilitate heat dissipation and observation, then the mashing tank is sealed and transferred to a koji incubation room, the temperature is set to 24-28°C, and the time is 20-28 hours, with the rice emitting a light sake aroma as the criterion;

[0028] (3) The rice with activated mashing yeast from step (2) is transferred to a low-temperature mashing room, the mashing yeast decomposes starch through aerobic mashing, the cover of the mashing tank is opened, and every 1-4 hours the sugar solution in the wine pits is scooped out and evenly poured onto the surface of the rice to keep the rice moist and also to cool the middle of the rice, the temperature in the mashing room is set to above 6°C to maintain the activity of root mold, and below 10°C to inhibit the activity of yeast, avoiding the decomposition of sugar and the protein on the outer layer of the rice by yeast, and also avoiding the production of acid by yeast to decompose fat, so as to ensure that the protein and fat on the outer layer of the rice and attached to the outer layer of the rice are completely preserved in a solid state at the end of mashing, mashing for 4 days, and when the starch residual rate of the rice is less than 5%, it is considered that mashing is complete;

[0029] (4) The mashing completed rice and mashing tank from step (3) are transferred to a fermentation room, water is added at a ratio of 1:1.2 based on the dry rice weight for the first fermentation, sealed for 48 hours, after the completion of fermentation, the fermented material liquid is taken out and pressed, the solid complete rice skin rich in protein and fat is separated out, and the clear liquid is pumped into a fermentation tank in the fermentation room for the second fermentation at a temperature of 18-22°C for 15 days to obtain the original liquid of Japanese sake;

[0030] (5) The original liquid of Japanese sake from step (4) after fermentation is completed is pumped into a sterilization tank, 500 g of bentonite is added per ton of original liquid of Japanese sake, the bentonite is dissolved uniformly in pure water at a weight ratio of 1:10 before being added into the original liquid of Japanese sake, stirring is started, the temperature is raised to 65°C, and kept for 30 minutes, then quickly cooled to 25°C, pumped into a sedimentation tank, and after 5 days of sedimentation, the bentonite is filtered to obtain Japanese sake with clear body, pure taste, light rice aroma, and a light green fruit aroma, which is transferred to a storage tank for aging for 10-15 days before being blended and canned for delivery.

[0031] The Japanese sake brewed in Example 1 has an actual alcohol content of 15.7%, a total sugar content of 1.3%, a total acid content of 0.28%, and an amino acid nitrogen content of 0.19%, and has a quality close to that of a pure rice Daiginjo. The total amount of the Japanese sake produced per ton of brown rice is 2.5 tons.

[0032] Example 2 provides a method for producing a Japanese sake. In order to obtain a Japanese sake having a purer taste, steps (1) to (3) are the same as in Example 1, and in step (4), the rice slurry in which saccharification is completed is removed and pressed, the rice husks are separated, and the clear liquid is adjusted to a sugar content of 35% with purified water and pumped into a fermentation tank to perform fermentation at a temperature of 18 to 22°C for 15 days. Then, the Japanese sake is subjected to sterilization and sedimentation filtration according to step (5) in Example 1.

[0033] The Japanese sake produced in Example 2 is a sweet-type Japanese sake, and has an alcohol content of 15%, a total sugar content of 7%, a total acid content of 0.25%, and an amino acid nitrogen content of 0.15%. The total amount of the Japanese sake produced per ton of brown rice is 2.2 tons.

[0034] Example 3 provides a method for producing a Japanese sake. In order to obtain a Japanese sake having a more intense rice flavor and a more mellow taste, steps (1) to (3) are the same as in Example 1, and in step (4), the rice slurry in which saccharification is completed and the saccharification tank are transferred to a fermentation workshop, water is added at a ratio of 1:1.3 based on the weight of the dry rice, and a first fermentation is performed in a sealed state at a temperature of 18 to 22°C for 7 days. After the first fermentation is completed, the fermented liquid and the rice slurry are removed and pressed to separate the outer layer of the rice, the fermented liquid is pumped into a fermentation tank, and a second fermentation is performed at a temperature of 18 to 22°C for 15 days. Then, the fermented liquid is pumped into a sterilization tank, stirring is started, the temperature is raised to 62 to 65°C, and the temperature is maintained for 28 to 32 minutes. Then, the temperature is rapidly lowered to 28°C, gelatin and purified water are dissolved at a ratio of 1:15 based on the weight, and the gelatin solution is added to the Japanese sake liquid at an amount of 300 g of gelatin per ton of the Japanese sake liquid, and the mixture is stirred for half an hour. Then, the mixture is pumped into a sedimentation tank, and the Japanese sake is allowed to stand for 3 days. Then, the Japanese sake is filtered using diatomaceous earth to obtain a Japanese sake having a clear body, a pure taste, and a delicate rice flavor. The Japanese sake is transferred to a storage tank, and is allowed to stand for 10 to 15 days to obtain a product.

[0035] The Japanese sake produced in Example 3 has an alcohol content of 16.5%, a total sugar content of 0.4%, a total acid content of 0.48%, and an amino acid nitrogen content of 0.45%. The total amount of the Japanese sake produced per ton of brown rice is 2.4 tons.

[0036] Comparative Example 1: The inventors of the present application conducted the following comparative test with respect to the saccharification temperature and the saccharification time.

[0037] Take 10 kg of ordinary rice, wash clean to water clear, soak for 7 hours, then drain the water, steam until cooked, pour cold water to cool to 22-28℃, then add sweet koji according to the proportion of 0.4% of the dry rice weight, then put into the saccharification tank, leave a wine nest in the middle of the rice for easy heat dissipation and observation, then seal the saccharification tank and transfer it to the incubation room, set the temperature to 24-28℃, and the time to 20-28 hours, then transfer the activated saccharification mold rice into the low-temperature saccharification workshop for aerobic saccharification, after saccharification, detect the reducing sugar content in the saccharification liquid, and record the reducing sugar content in the saccharification liquid under different saccharification time and saccharification temperature conditions, see Table 1 for details;

[0038] Table 1 is the effect comparison of different saccharification temperature and saccharification time on starch saccharification

[0039]

[0040] From the comparison data in Table 1, it can be seen that when the saccharification temperature is lower than 6℃, the starch conversion amount is lower, when it reaches 6℃, the starch conversion amount increases rapidly, when the saccharification temperature reaches 10℃, the yeast activity begins to recover, and the sugar source begins to consume, and when it exceeds 12℃, the sugar source consumption gradually increases; the starch conversion amount is less when the saccharification time is less than 3 days, and the sugar content in the saccharification liquid is low, when it reaches 3 days, the starch conversion rate gradually increases, and after 5 days, the increase in sugar content basically stops. Since the saccharification in the present application is carried out at low temperature, in order to reduce the production cost, the saccharification time is generally not more than 5 days. At the same time, the inventors recorded the carbon dioxide content in the saccharification workshop and the sensory in the workshop under different temperatures in the comparison examples, see Table 2 for details:

[0041] Table 2 Effect of different saccharification temperatures on microorganisms in sweet koji

[0042] Saccharification temperature Carbon dioxide content in the brewhouse during saccharification and off-flavour 5℃ Carbon dioxide content 0.04%, no off-flavour in the brewhouse 6℃ Carbon dioxide content 0.04%, no off-flavour in the brewhouse 9℃ Carbon dioxide content 0.04%, no off-flavour in the brewhouse 10℃ Carbon dioxide content 0.05%, no off-flavour in the brewhouse 12℃ Carbon dioxide content 0.08%, low off-flavour in the brewhouse 15℃ Carbon dioxide content 3%, suffocating, heavy off-flavour in the brewhouse

[0043] From the comparison data in Table 2, it can be seen that when the temperature reaches 10℃, the carbon dioxide in the workshop begins to increase, indicating that the yeast has begun to work, and when it reaches 12℃, the increase is very obvious, and when it reaches 15℃, the workshop has a obvious suffocating feeling.

[0044] Comparative Example 2: The inventors of the present application carried out the following comparison test on the fermentation time with grains, and the specific operation was completed according to steps (1) to (4) in Example 1, and the first fermentation time of the grains in step (4) was 0 to 7 days. After the first fermentation, the clear liquid was taken for detection, and the content of amino acid nitrogen was as shown in Table 3:

[0045] Table 3 Comparison of the content of amino acid nitrogen in the clear liquid with the first fermentation time of the grains

[0046]

[0047] It can be seen from the comparative example 2 that the time of the first fermentation with the lees directly affects the content of the amino acid nitrogen in the sake, thereby affecting the taste of the sake.

[0048] The present application uses ordinary rice as the raw material, does not need to remove the outer layer by grinding, directly soaks and cooks, firstly completes the saccharification of the rice starch by the temperature control of the saccharifying mold, and then obtains the Japanese sake with the pure taste, the clear wine body, the total acid, the amino acid nitrogen and the various sensory indexes meeting the Japanese sake style of the big brewing by the pressing after the fermentation with the lees or the direct pressing and the secondary fermentation of the clear liquid. The present application can obtain various styles of the Japanese sake brewing by adjusting the time of the first fermentation with the lees and controlling the different decomposition degrees of the yeast to the components such as the outer layer protein of the rice. It can be seen from the examples that the yield of the wine per ton of the unground brown rice is up to 2.5 tons, which is about 1.5 times higher than the yield of the wine of the existing Japanese sake, greatly improves the yield of the Japanese sake, reduces the raw material cost of the Japanese sake, does not need to additionally prepare the workshop, the equipment and the workers for the grinding of the outer layer of the rice, greatly reduces the production cost of the Japanese sake, and reduces the overall raw material and production cost by more than 50% compared with the existing Japanese sake production process.

Claims

1. A method for preparing sake using brown rice as raw material, characterized in that The specific steps are as follows: (1) Wash brown rice until the water is clear, then soak it in water for 4 to 8 hours; (2) drain the rice soaked in step (1), steam it, and then pour cold water over the rice until the temperature reaches 22-28°C. Add sweet wine yeast at a ratio of 0.3%-0.5% by weight of the dry rice, and then put it into a saccharification tank. Smooth the rice, leaving a dimple in the middle. After sealing, place it in a culture chamber at a temperature of 24-28°C to activate the saccharification mold for 20-28 hours. (3) The rice in which the saccharification mold has been activated in step (2) is transferred to a constant temperature saccharification chamber, and the temperature of the saccharification chamber is set to be greater than 6°C and less than 10°C. Under this temperature condition, the saccharification mold in the sweet wine koji decomposes starch into sugar liquid, and the yeast and other bacteria are in a low-temperature dormant state. The rice is opened for aerobic saccharification under low temperature conditions. The saccharification time is greater than 3 days and less than 5 days. When the residual starch rate of the rice is less than 5%, the saccharification is considered to be completed; during the saccharification process, the sugar liquid in the dimple is taken out and evenly poured onto the surface of the rice every 1 to 4 hours, and the rice is kept moist and allowed to stand; (4) directly pressing the rice saccharified in step (3) to separate the rice cortex containing protein and fat, then adding water to the pressed liquid to adjust the sugar content to 25% to 35%, and then fermenting it at room temperature for 10 to 15 days to obtain the sake stock solution; Alternatively, the saccharified rice in step (3) is added with water at a ratio of 1:0.5-2 by weight of dry rice, and the mixture is sealed and fermented for the first time at a temperature of 18-22°C for 1-7 days. The rice cortex containing protein and fat is then pressed with the liquid after the first fermentation is completed to separate the rice cortex, and the clear liquid is transferred to a fermentation tank and placed at room temperature for a second fermentation for 10-15 days to obtain a sake stock solution. (5) pasteurizing the sake stock solution obtained after fermentation in step (4) at 62-65°C, keeping the temperature for 28-32 minutes, then rapidly cooling to below 30°C, standing to clarify for 3-7 days, and filtering to obtain Japanese sake with a clear body and a pure and refreshing taste; (6) The Japanese sake prepared in step (5) is transferred to a wine storage tank for aging. After 10 to 15 days, it can be canned and shipped.

2. The method for preparing sake using brown rice as raw material according to claim 1, wherein: In the step (5), a precipitant is added in an amount of 300 g to 500 g per ton of sake stock solution during the sterilization process or after the sterilization is completed, and the precipitant is diluted with water and added to the sake stock solution; after clarification for 3 to 7 days, diatomaceous earth or bag filtration is used; when the precipitant is added during the sterilization process, the precipitant is bentonite; when the precipitant is added after the sterilization is completed, the precipitant is gelatin, chitosan, fish glue or egg white powder.

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