Bubble rice wine flavor upgrading process based on segmented temperature control fermentation

Abstract

The invention relates to the technical field of wine brewing engineering, and discloses a subsection temperature control fermentation-based bubble rice wine flavor upgrading process which comprises the following steps: firstly, gelatinizing glutinous rice, adding a component containing ultramicro citrus fiber and pectinase for enzymolysis modification, and constructing a bubble solid-liquid interface; adding a stress resistance regulator and compound yeast, and carrying out proliferation fermentation at 22-24 DEG C; then cooling to 10-12 DEG C, and standing to accumulate an ester precursor; raising the temperature to carry out dissolved oxygen pulse and nitrogen stripping; and finally, sealing and heating to 16-18 DEG C, and completing bubble stabilization by utilizing metabolism gas production. According to the method, the Pickering interface is constructed by utilizing the enzymolysis fiber, so that the bubble stability is effectively improved; by combining segmented temperature control with zinc ion regulation and control of metabolic flux, fusel oil generation is reduced, and ester accumulation is improved; yeast autolysis is prevented and volatile peculiar smell is removed by utilizing thermal oxygen pulse and nitrogen stripping, so that the bubble rice wine with fine and lasting bubbles, prominent ester fragrance and clean and refreshing taste is obtained.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of brewing engineering, in particular to a bubble rice wine flavor upgrading process based on segmented temperature control fermentation. BACKGROUND

[0002] Bubble rice wine is a new product in the low-alcohol wine market in recent years, which is based on the traditional rice wine brewing process and has both the mellow taste of rice wine and the refreshing taste of carbonated beverages by fermenting to produce gas or artificially charging carbon dioxide to give the wine body a certain pressure.

[0003] However, the existing production process of bubble rice wine products still has obvious limitations. In terms of bubble quality, most of the currently marketed products use the method of artificially injecting carbon dioxide under high pressure for carbonation. The combination of this exogenous gas and the wine body matrix is weak, resulting in large bubble diameter, rough and strong irritating taste, fast escape of bubbles after opening the bottle, and difficulty in forming a delicate and long-lasting bubble retention effect. Although some high-end products try to use in-bottle secondary fermentation process, due to the lack of hydrophobic foam proteins similar to barley malt in rice wine raw materials, the carbon dioxide produced by fermentation is difficult to form a stable bubble interface in the liquid phase, resulting in poor bubble stability. In order to improve this problem, the conventional method is to add thickening agents such as xanthan gum and agar, but this often increases the viscosity of the wine body, which destroys the refreshing taste that rice wine should have.

[0004] In terms of flavor quality, the traditional rice wine fermentation process cannot balance the bubble yield and aroma quality. In order to obtain sufficient dissolved carbon dioxide, it is usually necessary to maintain a high fermentation temperature to maintain yeast activity, but high-temperature fermentation will accelerate the Ehrlich metabolic pathway of amino acids, resulting in the generation of a large amount of higher alcohols such as isoamyl alcohol and isobutyl alcohol, thereby making the wine body have a bitter and off-flavor. On the contrary, if pure low-temperature fermentation is used, although it is beneficial to the retention of ester substances such as ethyl acetate, it will seriously inhibit the gas-producing metabolism of yeast, easily causing fermentation stagnation or insufficient mouthfeel of the final product. The existing fermentation control means lacks fine regulation of the metabolic flow direction of yeast, making it difficult to achieve both fine and sufficient bubbles and high-ester and low-alcohol flavor optimization goals at the same time. SUMMARY

[0005] In view of the deficiencies of the prior art, the present application provides a bubble rice wine flavor upgrading process based on segmented temperature control fermentation, which solves the technical problems of poor bubble stability and rough taste of existing bubble rice wine, and the difficulty of traditional fermentation process in balancing sufficient gas production with high-ester and low-alcohol flavor quality.

[0006] To achieve the above purpose, the present application is implemented by the following technical scheme: a bubble rice wine flavor upgrading process based on segmented temperature control fermentation, comprising the following steps:

[0007] Take 100 parts by weight of fine glutinous rice, after cooking and gelatinization, spread and cool, add 0.18-0.30 parts by weight of interface building components at 55-60℃ for enzyme modification, then add 0.4-0.6 parts by weight of saccharifying koji for saccharification;

[0008] The interface building components include ultra-micro citrus fiber and pectinase, and a solid-liquid interface of stable gas bubbles is constructed in the fermentation liquor through enzyme reaction;

[0009] Add 150-180 parts by weight of brewing water to the saccharified mash, adjust the pH value, add 0.005-0.01 parts by weight of stress resistance regulator, and inoculate 0.01-0.03 parts by weight of composite yeast inoculum, and carry out proliferation fermentation at 22-24℃;

[0010] Cool the fermentation mash to 10-12℃, and accumulate ester precursor substances by standing and fermenting at low temperature;

[0011] Warm up the mash, and pulse with sterile air for oxygen dissolution during the warming process, then immediately pulse with nitrogen for stripping treatment;

[0012] Seal the tank, continue to warm up to 16-18℃, use yeast metabolic gas to naturally increase pressure and maintain pressure, and complete bubble stabilization.

[0013] By adopting the above technical scheme, due to the synergistic effect of enzyme modification of ultra-micro citrus fiber and pectinase, segmented temperature control and stress resistance regulation, and thermal oxygen double pulse regulation, a rice wine product with fine and lasting bubbles and coordinated flavor is obtained. The specific mechanism is as follows:

[0014] In the substrate pretreatment stage, the ultra-micro citrus fiber is subjected to limited enzyme hydrolysis by pectinase. At 55-60℃, the pectinase hydrolyzes the high methoxyl pectin layer on the surface of the citrus fiber, exposing the hydrophobic cellulose microfilaments inside, so that the fiber particle surface presents an amphiphilic structure. The modified particles act as solid stabilizers and are adsorbed on the gas-liquid interface of carbon dioxide bubbles, forming a steric hindrance effect, inhibiting the coalescence and disproportionation of bubbles, and improving the stability of foam.

[0015] The yeast metabolism is regulated by segmented temperature control combined with stress resistance regulator strategy. At 22-24℃, zinc ions are added as cofactors of metal enzymes such as ethanol dehydrogenase to promote yeast proliferation; then the temperature is lowered to 10-12℃, and the low temperature environment inhibits the metabolic pathway of amino acid deamination to generate fusel oil, while maintaining the activity of alcohol acyltransferase, promoting the metabolic flow to the synthesis direction of acetate esters, reducing the content of higher alcohols and increasing the accumulation of ester substances.

[0016] The double pulse of heat and oxygen and nitrogen stripping step are introduced. In the late stage of low-temperature fermentation, the temperature is raised temporarily and sterile air is introduced. The dissolved oxygen promotes the synthesis of ergosterol and unsaturated fatty acid by yeast, maintains the cell membrane fluidity at low temperature, and reduces the bitter substances produced by cell autolysis; the subsequent nitrogen stripping reduces the dissolved oxygen content in the mash, and uses the gas-liquid equilibrium to carry out volatile substances such as acetaldehyde and hydrogen sulfide, thereby improving the flavor of the wine body.

[0017] The final pressure and temperature rising step realizes the interface stability of the bubbles. At 16-18℃ and autogenous pressure, the carbon dioxide microbubbles generated by yeast metabolism are combined with the fiber particles modified by enzymolysis, and a stable gas, solid and liquid three-phase system is constructed under pressure balance state to prevent carbon dioxide overflow.

[0018] Preferably, the interface construction component is an enzyme, fiber composite powder made of ultra-fine citrus fiber and pectinase mixed in a weight ratio of (3-7):1;

[0019] Preferably, the interface construction component is an enzyme, fiber composite powder made of ultra-fine citrus fiber and pectinase mixed in a weight ratio of (3-7):1;

[0020] By adopting the above technical solution, the ratio of fiber to enzyme and the cellulose content are controlled to ensure that the enzymolysis reaction degree is appropriate. If the enzyme amount is too high, the fiber skeleton is degraded too much; if the enzyme amount is too low, the surface hydrophobic group is not exposed enough. The ratio interval makes the modified fiber particles have the surface properties of constructing Pickering emulsion interface.

[0021] Preferably, the composite yeast inoculum is composed of ester-producing Saccharomyces cerevisiae and psychrotrophic Debenzyx holmii, and the cell number ratio of the two is (4-5):1.

[0022] The anti-stress regulator is food-grade zinc sulfate heptahydrate, and the addition amount of the anti-stress regulator makes the zinc ion concentration in the fermentation system be 5.0-8.0mg / L.

[0023] By adopting the above technical solution, the high ester-producing ability of Saccharomyces cerevisiae and the low-temperature tolerance of Debenzyx holmii are utilized. Zinc ion, as a structural component of zinc finger protein, up-regulates the expression of yeast heat shock protein gene at a concentration of 5.0-8.0mg / L, maintains the enzyme activity of the bacteria during temperature change, and reduces metabolic arrest.

[0024] Preferably, in the step of adding water to the saccharification mash, the pH value is adjusted as follows: using a pH adjuster selected from one of citric acid and sodium citrate buffer and lactic acid, the initial pH value of fermentation is adjusted to 5.5-5.8.

[0025] By adopting the above technical solution, a weakly acidic buffer system is constructed, which is in the enzyme activity interval of pectinase, improves the interface modification reaction efficiency, and at the same time inhibits the growth of miscellaneous bacteria and is beneficial to the absorption of zinc ions by yeast cells.

[0026] Preferably, the interface building component is added when the temperature of the glutinous rice is reduced to 55-60℃, and the reaction is maintained for 25-35 minutes.

[0027] The addition amount of the superfine citrus fiber is 0.15%-0.25% of the mass of the dry glutinous rice.

[0028] By using the above technical solution, the enzyme is hydrolyzed by using the residual heat during the temperature reduction after the gelatinization of the glutinous rice. The addition amount of 0.15%-0.25% of the fiber provides sufficient interface coverage area, and the viscosity of the liquor body is controlled.

[0029] Preferably, in the step of reducing the temperature to 10-12℃, the specific operation is that the temperature reduction rate is controlled to be 4-6℃ / h, the temperature is reduced from 22-24℃ to 10-12℃, and the fermentation is statically carried out for 48-60 hours under the current low temperature condition.

[0030] By using the above technical solution, the cold shock damage to the yeast is reduced by controlling the temperature reduction rate. The low-temperature static period of 48-60 hours is the ester synthesis stage, in which the intracellular enzyme catalyzes the conversion of acetyl coenzyme A and the substrate to synthesize flavor substances.

[0031] Preferably, the specific operation of the dissolved oxygen pulse and stripping treatment includes that when the temperature of the mash is increased to 12.5-13.0℃, sterile air is introduced to maintain the dissolved oxygen concentration at 1.5-2.5mg / L, and the process is continued for 15-20 minutes; then high-purity nitrogen gas is immediately switched to be introduced, and the gas flow rate is 0.1-0.2vvm, until the dissolved oxygen concentration is reduced to below 0.1mg / L.

[0032] By using the above technical solution, the dissolved oxygen of 1.5-2.5mg / L starts the sterol synthesis pathway without causing excessive oxidation of ethanol; the nitrogen gas stripping establishes an anaerobic environment to prevent the oxidation reaction from continuing, and physically removes volatile aldehyde substances.

[0033] Preferably, in the step of continuing to increase the temperature in the sealed tank, the specific operation condition is that the temperature increase rate is controlled to be 0.4-0.6℃ / h, the terminal temperature is 16-18℃, the absolute pressure in the tank is controlled to be 0.15-0.20MPa, and the process is maintained for 48-55 hours.

[0034] By using the above technical solution, the slow temperature increase and the increased pressure improve the solubility of carbon dioxide in the liquor. Under the pressure environment, the carbon dioxide molecules are distributed in the voids of the modified fiber network to form a stable colloidal structure.

[0035] Preferably, after the bubble stability is completed, the following step is further included: the fermentation liquor is cooled to 0-2℃, and is subjected to cross-flow filtration under the isobaric condition through a membrane with a pore size of 0.8-1.2μm, and the filtered liquor is subjected to low-temperature filling.

[0036] By adopting the technical scheme, the carbon dioxide is kept in a dissolved state at 0-2 DEG C, and the bacteria bodies and impurities are removed by isobaric cross-flow filtration, the micro-fiber components of the construction interface are reserved, and the clarity and foam retention of the wine body are ensured.

[0037] Preferably, the preparation method of the enzyme and fiber composite powder is as follows: the superfine citrus fiber and pectinase are placed in a V-type mixer, mixed for 25-35 minutes under the condition that the temperature is 18-22 DEG C and the relative humidity of the environment is 30%-40%, until the uniformity variation coefficient is less than 5%.

[0038] By adopting the technical scheme, the temperature and humidity of the environment are controlled, the pectinase is prevented from being inactivated or from having an unintended reaction due to moisture absorption, and the activity stability of the components is ensured.

[0039] The application provides a bubble rice wine flavor upgrading process based on segmented temperature control fermentation.

[0040] 1. The application constructs a stable bubble interface through enzymatic modification. The pectinase is used to directionally hydrolyze the superfine citrus fiber, expose the hydrophobic region inside the fiber, and convert it into an amphiphilic Pickering particle. During the fermentation and gas production process, the particle is adsorbed on the gas-liquid interface to form a mechanical barrier film, which inhibits the coalescence and disproportionation of bubbles, thereby improving the foam fineness and durability of the bubble rice wine without relying on chemical surfactants.

[0041] 2. The application realizes directional regulation of fermentation metabolic flow and optimizes the composition of wine flavor substances. Through the segmented temperature control strategy combined with stress resistance regulators, zinc ions are used to ensure yeast proliferation activity in the early fermentation stage, and a low-temperature environment is used to inhibit the metabolic branch of amino acid deamination to produce fusel oil in the later stage, while maintaining the activity of alcohol acyltransferase and promoting the accumulation of aroma substances such as isoamyl acetate, thereby solving the problems of high fusel oil content and rough taste in traditional rice wine.

[0042] 3. The application improves the purity and harmony of the wine body through the heat-oxygen double pulse and nitrogen stripping process. The micro-oxygen supply in the late low-temperature fermentation stage promotes the synthesis of cell membrane sterols of yeast cells, maintains the low-temperature tolerance of cells, prevents the generation of bitter peptides due to cell autolysis, and cooperates with nitrogen stripping treatment to remove volatile off-flavor substances such as acetaldehyde and hydrogen sulfide, thereby avoiding the residual of greenish and sulfury odors, and improving the sensory quality of the product. DETAILED DESCRIPTION

[0043] The technical solutions in the embodiments of the present application will be described clearly and completely below in combination with the preparation examples, embodiments, test examples and test cases of the present application. Obviously, the described embodiments are only some of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative efforts belong to the scope of protection of the present application.

[0044] Preparation Example 1-3:

[0045] Preparation Example 1:

[0046] The present preparation example provides a preparation method of an enzyme and fiber composite powder for interface modification of bubble rice wine, comprising the following steps:

[0047] Accurately weigh 1000 g of superfine citrus fiber (particle size D90 less than 20 μm, insoluble cellulose content 48%) and 200 g of pectinase (enzyme activity 30,000 U / g); place the above raw materials in a clean and dry V-type mixer, mix for 30 minutes at a temperature of 20℃ and a relative humidity of less than 40%, until the variation coefficient of mixing uniformity is less than 5%; package the mixed powder under sterile conditions, seal and package with vacuum aluminum foil bags, to obtain the enzyme and fiber composite powder, which is stored in a dry and dark environment at 4℃ for standby.

[0048] Preparation Example 2:

[0049] The present preparation example provides a preparation method of an enzyme and fiber composite powder for interface modification of bubble rice wine, comprising the following steps:

[0050] Accurately weigh 800 g of superfine citrus fiber (particle size D90 less than 20 μm, insoluble cellulose content 46%) and 250 g of pectinase (enzyme activity 30,000 U / g); place the above raw materials in a clean and dry V-type mixer, mix for 30 minutes at a temperature of 20℃ and a relative humidity of less than 40%, until the variation coefficient of mixing uniformity is less than 5%; package the mixed powder under sterile conditions, seal and package with vacuum aluminum foil bags, to obtain the enzyme and fiber composite powder, which is stored in a dry and dark environment at 4℃ for standby.

[0051] Preparation Example 3:

[0052] The present preparation example provides a preparation method of an enzyme and fiber composite powder for interface modification of bubble rice wine, comprising the following steps:

[0053] Accurately take 1200 g of ultra-fine citrus fiber (particle size D90 less than 20 μm, insoluble cellulose content 50%) and 180 g of pectinase (enzyme activity 30,000 U / g); place the above raw materials in a clean and dry V-type mixer, mix for 30 minutes at a temperature of 20℃ and a relative humidity of less than 40%, until the uniformity coefficient of the mixture is less than 5%; package the mixed powder under sterile conditions, seal the package with a vacuum aluminum foil bag, and obtain an enzyme and fiber composite powder, which is stored in a dry and dark environment at 4℃ for standby use.

[0054] Examples 1-4:

[0055] Example 1:

[0056] The present embodiment provides a bubble rice wine flavor upgrading process based on segmented temperature control fermentation, which comprises the following steps:

[0057] S1, substrate pretreatment and enzyme modification interface construction:

[0058] Take 100 kg of fine glutinous rice, wash and soak in water for 14 hours, then drain and cook under normal pressure for 35 minutes until the rice is completely gelatinized; when the temperature of the cooked glutinous rice drops to 58℃, uniformly add 240 g of the composite interface modifier obtained in Preparation Example 1 (addition amount is 0.24% of the dry rice mass), mix well, and then use the residual heat to keep the reaction for 30 minutes; then quickly cool to 30℃, add 500 g of Rhizopus mold, and incubate at 30℃ for 28 hours of solid state saccharification.

[0059] S2, fermentation start and stress resistance adaptation:

[0060] After saccharification, add 160 kg of sterile water (material to water ratio about 1:1.6) to the fermentation tank, adjust the initial sugar content of the mash to 19.0°Bx, and use citric acid and sodium citrate buffer to adjust the pH value to 5.6; add 7.0 g of food-grade zinc sulfate heptahydrate to the mash, so that the zinc ion concentration in the system is about 6.0 mg / L; accurately take 20.0 g of dry composite yeast inoculant (equivalent to 0.02% of the dry rice mass, containing 16.0 g of ester-producing Saccharomyces cerevisiae and 4.0 g of Brettanomyces), activate and inoculate into the fermentation tank; at this time, the corresponding initial total inoculum is about 1.5×10^6 CFU / mL, and the inoculation ratio is 4:1 of cell number; start stirring (speed 40 rpm), and carry out fermentation and proliferation at 23℃ for 28 hours to make the yeast population reach the maximum biomass reserve.

[0061] S3, gradient cold shock and metabolic redirection: pass-5℃ ethylene glycol coolant through the jacket, control the cooling rate at 5℃ / h, and reduce the fermentation mash temperature from 23℃ to 11℃ within 2.5 hours; stop stirring and incubate at 11℃ for 54 hours to induce the yeast to enter the metabolic adjustment period in the low temperature environment.

[0062] S4, heat and oxygen double pulse regulation and nitrogen stripping:

[0063] Turn on the program to raise the temperature, set the temperature rising rate to 0.5℃ / h, and the target end temperature to 17℃; when the temperature of the mash rises to 12.8℃, open the micron-level aeration device at the bottom of the tank, and blow sterile air to pulse the dissolved oxygen, control the dissolved oxygen concentration to 2.0mg / L, and maintain for 15 minutes; after the dissolved oxygen pulse is over, immediately switch the pipeline to blow off high-purity nitrogen gas, set the nitrogen flow to 0.15vvm, and continue to blow off for 12 minutes, until the online detection of dissolved oxygen value is less than 0.1mg / L, to ensure that the system quickly returns to a strict anaerobic state.

[0064] S5, pressure rise and interface self-assembly:

[0065] Close the inlet valve to seal the tank, and continue to maintain a temperature rising rate of 0.5℃ / h to 17℃; use the gas produced by yeast metabolism to naturally increase the pressure, and control the absolute pressure in the tank to maintain at 0.18MPa, keep for 50 hours under this temperature and pressure condition, and use the pressure environment to strengthen the dissolution and adsorption of gas bubbles in the modified colloid.

[0066] S6, cross-flow filtration and product packaging:

[0067] Cool the fermentation broth to 1℃ at a rate of 1.2℃ / h, and stand for 48 hours at 0.18MPa pressure; then under isobaric conditions, make the wine pass through an alumina ceramic membrane with a pore size of 0.8μm for cross-flow filtration, control the transmembrane pressure difference to be 0.08MPa; the filtrate is filled into glass bottles under low temperature and isobaric conditions, and is sealed by pressing the lid, to obtain a clear bubble rice wine.

[0068] Example 2:

[0069] The present embodiment provides a bubble rice wine flavor upgrading process based on segmented temperature control fermentation, which comprises the following steps:

[0070] S1, substrate pretreatment and enzyme modification interface construction:

[0071] Take 100kg of fine glutinous rice, wash and soak in water for 12 hours, then drain and cook under normal pressure for 30 minutes until the rice is completely gelatinized; when the temperature of the cooked glutinous rice drops to 55℃, evenly add 200g of the composite interface modifier obtained in Preparation Example 2 (the addition amount is 0.20% of the dry rice mass, which contains about 0.15% of ultra-fine citrus fiber), mix evenly, and then use the residual heat to keep warm for 25 minutes; then quickly cool to 28℃, and inoculate 400g of Rhizopus koji, incubate and solidify at 30℃ for 24 hours.

[0072] S2, fermentation start and stress resistance adaptation:

[0073] After saccharification, 150 kg of sterile water was added to the fermenter (material to water ratio of about 1:1.5), and the initial sugar content of the mash was adjusted to 18.0 °Bx. Lactic acid was used to adjust the pH value to 5.5. Food-grade zinc sulfate heptahydrate 5.5 g was added to the mash to make the zinc ion concentration in the system about 5.0 mg / L. Compound yeast agent dry powder 12.5 g (equivalent to 0.0125% of the dry rice mass, containing ester-producing Saccharomyces cerevisiae 10.0 g and Brettanomyces 2.5 g) was accurately weighed and inoculated into the fermenter after activation. At this time, the corresponding initial total inoculum was about 1.0 × 10^6 CFU / mL, and the inoculation ratio was 4:1. Stirring was started (rotation speed 30 rpm), and fermentation and proliferation were carried out at 22°C for 24 hours.

[0074] S3, gradient cold shock and metabolic redirection:

[0075] The jacket was connected to -5°C ethylene glycol coolant to control the cooling rate at 6°C / h, and the temperature of the fermentation mash was reduced from 22°C to 10°C within 2 hours. Stirring was stopped, and the mash was incubated at 10°C for 48 hours. The metabolic activity and precursor accumulation of the yeast were tested at the lower temperature limit.

[0076] S4, heat and oxygen double pulse control and nitrogen stripping:

[0077] The program was started to increase the temperature, and the temperature was set to increase at a rate of 0.4°C / h, with a target end temperature of 16°C. When the mash temperature rose to 12.5°C, the micron-sized aeration device at the bottom of the tank was turned on, and sterile air was introduced for dissolved oxygen pulse control. The dissolved oxygen concentration was controlled at 1.5 mg / L, and the maintenance time was 15 minutes. After the dissolved oxygen pulse was completed, the pipeline was immediately switched to high-purity nitrogen gas for stripping. The nitrogen flow rate was set to 0.10 vvm, and the stripping was continued for 10 minutes until the online dissolved oxygen value was less than 0.1 mg / L.

[0078] S5, pressure increase and interface self-assembly:

[0079] The inlet valve was closed to seal the tank, and the temperature was continued to increase at a rate of 0.4°C / h to 16°C. The absolute pressure in the tank was maintained at 0.15 MPa using the gas produced by yeast metabolism. The temperature and pressure were maintained for 48 hours.

[0080] S6, cross-flow filtration and product packaging:

[0081] The fermentation broth was cooled to 0°C at a rate of 1.5°C / h, and was incubated for 48 hours at 0.15 MPa. Then, under isobaric conditions, the wine was filtered through a polyether sulfone membrane with a pore size of 1.2 μm to perform cross-flow filtration, and the transmembrane pressure difference was controlled at 0.05 MPa. The filtrate was filled into glass bottles under low-temperature isobaric conditions, and the bottles were sealed by pressing the lid. Thus, clear sparkling rice wine was obtained.

[0082] Example 3:

[0083] The present embodiment provides a bubble rice wine flavor upgrading process based on segmented temperature control fermentation, which comprises the following steps:

[0084] S1, substrate pretreatment and enzyme modification interface construction:

[0085] Take 100 kg of fine glutinous rice, wash and soak in water for 16 hours, then drain and cook under normal pressure for 40 minutes until the rice is completely gelatinized; when the temperature of the cooked glutinous rice drops to 60°C, evenly add 250 g of the composite interface modifier obtained in Preparation Example 3 (the addition amount is 0.25% of the dry rice mass, which contains about 0.217% of ultra-fine citrus fiber), mix well and then use the residual heat to react for 35 minutes; then quickly cool to 30°C, add 600 g of Rhizopus koji, and incubate at 30°C for 30 hours.

[0086] S2, fermentation start and stress resistance adaptation:

[0087] After saccharification, add 180 kg of sterile water to the fermentation tank (the material to water ratio is about 1:1.8), adjust the initial sugar content of the mash to 20.0 °Bx, and adjust the pH value to 5.8 using citrate buffer; add 9.9 g of food-grade zinc sulfate heptahydrate to the mash, so that the zinc ion concentration in the system is about 8.0 mg / L; accurately weigh 28.0 g of composite yeast agent dry powder (equivalent to 0.028% of the dry rice mass, which contains 22.4 g of ester-producing Saccharomyces cerevisiae and 5.6 g of Brettanomyces), activate and then inoculate into the fermentation tank; at this time, the corresponding initial inoculation amount is about 2.0 x 10^6 CFU / mL, and the inoculation ratio is 4:1; start stirring (speed 50 rpm), and carry out fermentation and proliferation at 24°C for 30 hours to promote biomass accumulation in a high-concentration substrate environment.

[0088] S3, gradient cold shock and metabolic redirection:

[0089] Control the cooling rate at 4°C / h by passing -5°C ethylene glycol coolant through the jacket, and reduce the fermentation mash temperature from 24°C to 12°C within 3 hours; stop stirring and incubate at 12°C for 60 hours to verify the effect of metabolic flow redirection under milder cold shock conditions.

[0090] S4, hot and oxygen double pulse regulation and nitrogen stripping:

[0091] Start the temperature rising program, set the temperature rising rate to 0.6℃ / h, and the target end temperature to 18℃; when the temperature of the mash rises to 13.0℃, open the micron-level aeration device at the bottom of the tank, and pulse the dissolved oxygen by blowing sterile air, control the dissolved oxygen concentration to 2.5mg / L, and maintain for 20 minutes; after the dissolved oxygen pulse is over, immediately switch the pipeline to blow off by blowing high-purity nitrogen gas, set the nitrogen flow rate to 0.20vvm, and continue blowing off for 15 minutes until the online detection of the dissolved oxygen value is less than 0.1mg / L.

[0092] S5, temperature rising with pressure and interface self-assembly:

[0093] Close the inlet valve to seal the tank, and continue to maintain the temperature rising rate of 0.6℃ / h to 18℃; use the gas produced by yeast metabolism to naturally increase the pressure, control the absolute pressure in the tank to maintain at 0.20MPa, and maintain at a relatively high temperature and pressure for 55 hours to test the stability of the bubble structure under high pressure.

[0094] S6, cross-flow filtration and product packaging:

[0095] Cool the fermentation broth to 2℃ at a rate of 1.0℃ / h, and stand for 72 hours at 0.20MPa pressure; then under isobaric conditions, make the wine pass through an alumina ceramic membrane with a pore size of 0.8μm for cross-flow filtration, control the transmembrane pressure difference to 0.10MPa; the filtrate is filled into glass bottles under low temperature and isobaric conditions, and is sealed by pressing the lid, to obtain a clear bubble rice wine.

[0096] Example 4:

[0097] The present embodiment provides a bubble rice wine flavor upgrading process based on segmented temperature control fermentation, which comprises the following steps:

[0098] S1, substrate pretreatment and enzyme modification interface construction:

[0099] Take 100kg of fine glutinous rice, wash and soak in water for 14 hours, then drain and cook under normal pressure for 35 minutes until the rice is completely gelatinized; when the cooked glutinous rice is cooled to 56℃, evenly add 240g of the composite interface modifier obtained in Preparation Example 1 (the addition amount is 0.24% of the dry rice mass), mix evenly, and then use the residual heat to maintain the reaction for 30 minutes; then quickly cool to 30℃, and inoculate 550g of Rhizopus koji, and incubate at 30℃ for 26 hours for solid state saccharification.

[0100] S2, fermentation start and stress resistance adaptation:

[0101] After the end of saccharification, 170 kg of sterile water was added to the fermenter (material to water ratio about 1:1.7), the initial sugar content of the mash was adjusted to 19.0 °Bx, and 85% food-grade lactic acid was used to adjust the pH value to 5.5 (instead of buffer salt to verify the applicability of the acidity regulator); 7.0 g of food-grade zinc sulfate heptahydrate was added to the mash to make the zinc ion concentration in the system about 6.0 mg / L; 16.2 g of dry composite yeast inoculant (equivalent to 0.0162% of the dry rice mass, containing 13.5 g of ester-producing Saccharomyces cerevisiae and 2.7 g of Brettanomyces) was accurately weighed and added to the fermenter after activation; at this time, the corresponding initial total inoculum was about 1.2 × 10^6 CFU / mL, and the inoculum ratio was adjusted to 5:1; the stirring was started (rotation speed 40 rpm), and the fermentation and proliferation were carried out at 23°C for 26 hours.

[0102] S3, gradient cold shock and metabolic redirection:

[0103] The jacket was connected to -5°C ethylene glycol coolant to control the cooling rate at 5°C / h, and the fermentation mash temperature was reduced from 23°C to 11°C in 2.5 hours; the stirring was stopped, and the fermentation was carried out at 11°C for 50 hours under constant temperature conditions to verify the effect of low temperature stress on the accumulation of metabolic products after the strain ratio was adjusted.

[0104] S4, heat and oxygen double pulse regulation and nitrogen stripping:

[0105] The program was started to increase the temperature, and the temperature increase rate was set to 0.5°C / h with a target endpoint temperature of 17°C; when the mash temperature rose to 12.8°C, the micron-sized aeration device at the bottom of the tank was started, sterile air was introduced for dissolved oxygen pulse, the dissolved oxygen concentration was controlled at 2.0 mg / L, and the maintenance time was 15 minutes; after the dissolved oxygen pulse was completed, the pipeline was immediately switched to high-purity nitrogen gas for stripping, the nitrogen gas flow was set to 0.15 vvm, and the stripping was continued for 12 minutes until the online detection of dissolved oxygen value was less than 0.1 mg / L.

[0106] S5, pressure increase and temperature increase and interface self-assembly: the inlet valve was closed to seal the tank, and the temperature increase rate of 0.5°C / h was continued to 17°C; the absolute pressure in the tank was maintained at 0.18 MPa by using the gas produced by yeast metabolism to naturally increase the pressure, and the temperature and pressure conditions were maintained for 50 hours.

[0107] S6, cross-flow filtration and product packaging:

[0108] The fermentation broth was cooled to 1°C at a rate of 1.0°C / h, and was allowed to stand for 48 hours under 0.18 MPa pressure; then under isobaric conditions, the wine was passed through an alumina ceramic membrane with a pore size of 0.8 μm for cross-flow filtration, and the transmembrane pressure difference was controlled at 0.08 MPa; the filtrate was filled into glass bottles under low-temperature isobaric conditions, and was sealed by pressing the lid, to obtain clear sparkling rice wine.

[0109] Comparative Example 1-8:

[0110] Comparative Example 1:

[0111] Compared with Example 1, the difference lies in that a traditional constant temperature fermentation process is adopted. Specifically, it is characterized by:

[0112] No composite interface modifier is added in the substrate pretreatment stage (i.e. no addition of ultra-fine citrus fiber and pectinase);

[0113] The temperature is kept at 25℃ throughout the fermentation process, without gradient cold shock, heat and oxygen pulse and pressure raising operation, and the fermentation is directly filtered after completion.

[0114] Comparative Example 2:

[0115] Compared with Example 1, the difference lies in that no composite interface modifier is added in the substrate pretreatment stage, and the rest of the process steps are exactly the same.

[0116] Comparative Example 3:

[0117] Compared with Example 1, the difference lies in that only ultra-fine citrus fiber is added in the substrate pretreatment stage, and no pectinase is added, and the rest is the same.

[0118] Comparative Example 4:

[0119] Compared with Example 1, the difference lies in that the gradient cold shock and metabolic redirection steps are not performed. After the fermentation is started, it is maintained at 23℃ constant temperature fermentation to the end, and the rest of the interface construction and subsequent filtration steps are the same.

[0120] Comparative Example 5:

[0121] Compared with Example 1, the difference lies in that the heat and oxygen pulse step is not performed. The fermentation tank is strictly sealed during the temperature raising process, and no sterile air is introduced, and the rest is the same.

[0122] Comparative Example 6:

[0123] Compared with Example 1, the difference lies in that the nitrogen stripping step is not performed. After the sterile air is introduced for 15 minutes of oxygen pulse, the nitrogen stripping is not switched, and the tank is directly sealed for pressure raising, and the rest is the same.

[0124] Comparative Example 7:

[0125] Compared with Example 1, the difference lies in that no stress resistance regulator is added in the fermentation start-up stage, and the rest is the same.

[0126] Comparative Example 8:

[0127] Compared with Example 1, the difference lies in that: only ester-producing Saccharomyces cerevisiae is inoculated in the fermentation starting stage, and no Psychrophilic Brettanomyces is inoculated, the total amount of inoculation is unchanged, and the rest is the same.

[0128] Test Example 1-5:

[0129] Test Example 1: Fermentation kinetics and stress resistance performance monitoring

[0130] Experimental description:

[0131] The experiment aims to monitor the key kinetic parameters and microbial physiological indicators in the fermentation process, and evaluate the effects of stress resistance factor addition, double strain compounding and heat and oxygen pulse operation on the metabolic activity and survival state of yeast in the variable temperature and pressure environment. The experimental objects are selected from Example 1, Example 4, Comparative Example 5, Comparative Example 7 and Comparative Example 8.

[0132] The specific experimental steps are as follows:

[0133] Take the wort samples at different fermentation stages, and set the sampling points as follows: the end of gradient cold shock, the time when the temperature is raised to 15℃ under pressure, and the end of fermentation.

[0134] For the samples at the end of gradient cold shock and the time when the temperature is raised to 15℃ under pressure, methylene blue staining method combined with hemocytometer is used for microscopic counting to calculate the survival rate of yeast cells, so as to evaluate the physiological activity retention of yeast during low temperature stress and subsequent temperature rise.

[0135] Using the online pressure sensor of the fermentation tank, record the change of the pressure in the tank during the pressure raising stage (stage three) at intervals of 10 minutes, calculate the average pressure rising rate of this stage, and use it to represent the CO2 gas production metabolic capacity of yeast in high pressure environment.

[0136] At the end of fermentation, take the sample and centrifuge, filter the supernatant through a 0.45 μm filter membrane, and then use DNS colorimetric method to determine the residual sugar content, so as to evaluate the completeness of fermentation.

[0137] Experimental data:

[0138] Table 1: Statistics of yeast stress resistance performance and fermentation kinetic parameters under different process conditions

[0139]

[0140] Conclusion analysis:

[0141] According to the data in Table 1, Example 1 and Example 4 show high stability and consistency in various indicators. The yeast survival rate after the end of cold shock is maintained at more than 93%, the final residual sugar is less than 2.5 g / L, and the in-tank pressure successfully reaches the set target (about 0.18 MPa). This indicates that the process parameters of the present application have good robustness, which can ensure that the fermentation is carried out completely.

[0142] In contrast, the data of Comparative Example 7 shows metabolic inhibition. Its survival rate after the end of cold shock is only 61.4%, and the pressure rise rate during the warming-up period is low, resulting in a final residual sugar of 16.3 g / L, and the fermentation is in a semi-stopped state. This result confirms the key mechanism of zinc ions in the system: Zn 2+ As a cofactor of zinc finger protein in yeast, it directly participates in the transcriptional regulation of heat shock proteins. Without the supplement of zinc ions, yeast cannot effectively synthesize protective proteins to cope with low temperature stress, resulting in a large number of cell death or entering a dormant state, which cannot maintain the subsequent gas production metabolism.

[0143] Although the survival rate of Comparative Example 5 in the cold shock stage (88.5%) is acceptable, the pressure rise rate during the warming-up period is significantly lower than that of Example 1, and the final residual sugar is slightly high. This verifies the necessity of heat and oxygen pulses. In a micro-oxygen environment, yeast uses oxygen to synthesize ergosterol and unsaturated fatty acids, which are embedded in the phospholipid bilayer of the cell membrane, regulating the fluidity and permeability of the membrane. Without this step, the yeast cell membrane cannot quickly recover its fluidity after cold shock, causing the transmembrane transport of nutrients to be blocked, limiting the metabolic activity of yeast during the subsequent pressure warming process, resulting in a fermentation tailing phenomenon.

[0144] The data of Comparative Example 8 shows that a single S. cerevisiae has poor adaptability in a low-temperature environment, with a survival rate of only 54.8%. Due to the lack of the synergistic effect of P. cryoholicum, the metabolic activity of the system almost stops at a low temperature of 10-12℃. Although the metabolic rate increases after warming (0.0024 MPa / h, higher than that of Comparative Example 7), due to the excessive loss of biomass in the early stage, it is not possible to establish a sufficient pressure environment, and the residual sugar is not completely consumed.

[0145] In summary, the three factors of zinc ion stress resistance, temperature relay of double strains, and repair of membrane performance by heat and oxygen pulses are indispensable and jointly constitute the basis of the efficient and complete temperature control fermentation mechanism of the present application.

[0146] Test Example 2: Dissolved oxygen (DO) and acetaldehyde metabolic dynamic analysis

[0147] Experimental description:

[0148] The experiment focuses on the control effect of heat and oxygen pulse and nitrogen stripping process on the oxidation-reduction environment and volatile aldehyde substances in the fermentation system. Example 1, Comparative Example 5 and Comparative Example 6 are selected as test objects.

[0149] The specific operation steps are as follows:

[0150] During the heat and oxygen double pulse regulation stage of the process flow, the dissolved oxygen concentration in the mash is collected in real time by using the polarographic dissolved oxygen electrode installed at the bottom of the fermentation tank. The data at the end of the oxygen pulse (after 15 minutes of aeration) and at the end of the subsequent process operation (after nitrogen stripping in Example 1, and after natural standing for the same length of time in Comparative Example 6) are recorded.

[0151] Corresponding to the above two time nodes, the mash samples are collected aseptically through the sampling valve. The samples are immediately placed in an ice bath to cool to inhibit the reaction, and then an internal standard (2-pentanone) is added. The acetaldehyde content in the samples is determined by headspace solid-phase microextraction combined with gas chromatography-mass spectrometry.

[0152] After the fermentation and post-ripening process is completed, the final product wine sample is collected. The final acetaldehyde residual amount is determined, and the absorbance value at 420 nm wavelength is determined using a spectrophotometer as an evaluation index of wine body color and oxidation browning degree.

[0153] Experimental data:

[0154] Table 2: Monitoring data of dissolved oxygen, acetaldehyde content and colority under different gas regulation strategies

[0155]

[0156] Conclusion analysis:

[0157] According to the data in Table 2, by performing the dissolved oxygen and stripping double pulse operation, Example 1 realizes the dual control of oxidation risk and metabolic byproducts. At the end of the dissolved oxygen pulse, the dissolved oxygen concentration reaches 2.14 mg / L, and the acetaldehyde content temporarily rises to 38.5 mg / L (partly due to the accumulation of intermediate metabolic products of yeast under aerobic conditions), but in the subsequent nitrogen stripping step, the dissolved oxygen concentration quickly drops to 0.06 mg / L, indicating that the system quickly returns to a strict anaerobic state. The acetaldehyde content in the final product wine is only 14.2 mg / L, and the colority of the finished product wine is maintained at a low level of 0.115, indicating that the nitrogen flow not only physically strips part of the volatile acetaldehyde, but more importantly, it cuts off the chemical path of ethanol oxidation to acetaldehyde.

[0158] The data of Comparative Example 6 revealed the severe consequences of lacking a stripping step after the oxygen pulse. Although its dissolved oxygen concentration and acetaldehyde level at the end of the pulse were similar to Example 1, the dissolved oxygen concentration remained at a high level of 1.85 mg / L in the subsequent stages due to the lack of nitrogen replacement. This led to the residual oxygen continuously oxidizing the phenols and ethanol in the wine body, resulting in the acetaldehyde content in the finished wine soaring to 92.4 mg / L, and the color of the finished wine reaching as high as 0.421, showing obvious signs of oxidative browning. This confirmed that a simple micro-aerobic treatment would destroy the reducing stability of the wine body without the cooperation of nitrogen stripping.

[0159] The final acetaldehyde content of Comparative Example 5 was 48.7 mg / L, higher than Example 1. Although this group did not introduce exogenous oxygen, the acetaldehyde content instead accumulated. This echoed the conclusion of the aforementioned Test Example 1: due to the lack of micro-aerobic stimulation, the poor membrane fluidity of the yeast cells led to the decline in their enzymatic reaction capacity to reduce acetaldehyde to ethanol in the late fermentation stage, resulting in the retention of fermentation byproducts.

[0160] In summary, the nitrogen stripping step adopted in Example 1 is not a simple deoxidation operation, but a key process based on the principle of gas-liquid equilibrium, which simultaneously removes dissolved oxygen and volatile aldehydes using the pressure difference of high-purity nitrogen. This mechanism effectively solves the common oxidative side effects in the micro-aerobic propagation process, while maintaining the sensory quality of the clear and light color of the bubble rice wine while ensuring the vitality of the yeast.

[0161] Test Example 3: Bubble Macroscopic Property and Colloid Stability Test

[0162] Experimental Description:

[0163] This experiment aimed to evaluate the effects of enzyme and fiber interface modification systems on bubble stability and wine clarity from the macro-physical level. Example 1-3, Comparative Example 2, and Comparative Example 3 were selected as test objects.

[0164] The specific operation steps are as follows:

[0165] Place the finished wine samples of each group in a 4°C constant temperature water bath for 24 hours to ensure consistent initial temperature during testing.

[0166] Using the standard pouring method, pour 500 mL of wine sample from a height of 10 cm above the bottom of a clean and dry 1000 mL graduated cylinder along the wall, and record the maximum height after foam generation and the liquid emptying time.

[0167] Record the time required for the foam layer height to decay from the initial maximum value to half of its height, which is referred to as the foam half-life, to represent the persistent stability of the foam; after 5 minutes of standing, measure the thickness of the residual foam layer using a vernier caliper, which is referred to as the bubble retention height.

[0168] Part of the sample was treated by ultrasonic degassing, and then the turbidity value of the wine body was measured by using a portable turbidity meter to evaluate the colloidal stability.

[0169] Another unopened sample was used to measure the amount of dissolved carbon dioxide in the wine liquid using a CO2 analyzer to evaluate the system's ability to adsorb and retain gas.

[0170] Experimental data:

[0171] Table 3: Bubble properties and colloidal index test results under different interface construction conditions

[0172]

[0173] Conclusion analysis:

[0174] According to the data in Table 3, there is an order of magnitude difference in bubble performance between Examples 1-3 and Comparative Example 2. The half-life of the foam of Comparative Example 2 is only 42 seconds, and the CO2 dissolution amount is 2.75 g / L, indicating that in the absence of ultra-micro citrus fiber as a solid skeleton, there is a lack of heterogeneous nucleation sites in the system. CO2 is difficult to exist stably in the form of fine bubbles in the liquid phase, and is mostly lost in the form of large molecules, resulting in insufficient mouthfeel and poor bubble retention performance. In contrast, the half-life of Example 1 is extended to 187 seconds, and the CO2 dissolution amount is increased to 4.82 g / L, confirming that insoluble cellulose particles effectively reduce the Gibbs free energy change of bubble formation, playing a role in physically anchoring bubbles.

[0175] The data of Comparative Example 3 highlights the decisive role of enzymatic modification in colloidal stability. Although Comparative Example 3 has an improved foam half-life and CO2 dissolution amount after adding fibers compared to Comparative Example 2, its turbidity value is as high as 14.25 EBC, showing a visible cloudy state. This is because the surface of the citrus fiber without pectinase treatment is combined with a large amount of water-soluble pectin and hemicellulose, which forms an unstable colloidal suspension in the wine, resulting in severe haze.

[0176] Example 1 reduces the turbidity to 0.65 EBC while maintaining high bubble stability, close to the clarity level. This verifies the synergistic mechanism of enzymes and fibers: pectinase specifically hydrolyzes the polygalacturonic acid chains on the surface of the fiber, eliminating the pectin layer that causes turbidity and reducing steric hindrance. This modification not only clarifies the wine body, but more importantly, it exposes the hydrophobic cellulose region inside the fiber. These hydrophobic microzones serve as excellent gas adsorption interfaces, enhancing the binding of CO2, thereby achieving the goal of improving bubble quality without introducing turbidity. The data trends of Examples 2 and 3 show that as the amount of fiber added increases, bubble stability is enhanced, but turbidity increases slightly, and the ratio of Example 1 achieves the best balance between the two.

[0177] Test Example 4: Flavor substance spectrum analysis

[0178] Experimental description:

[0179] In this experiment, headspace solid-phase microextraction combined with gas chromatography-mass spectrometry was used to qualitatively and quantitatively analyze the volatile flavor substances in the finished wine, focusing on the regulation of gradient chilling and metabolic redirection processes on the synthesis of ester flavor substances and the generation of higher alcohols. The experimental objects were the finished wine samples of Example 1, Comparative Example 1 and Comparative Example 4.

[0180] The specific operation steps are as follows:

[0181] Accurately take 8.0 mL of wine sample and place it in a 20 mL headspace sampling bottle, add 2.5 g of sodium chloride to achieve saturated salting effect, then add 20 μL of 4-methyl-2-pentanol with a concentration of 400 mg / L as an internal standard, seal with a cap and place it on a magnetic stirring heating table, and equilibrate at 45°C for 15 minutes.

[0182] Insert the aged extraction head, and under constant temperature conditions at 45°C, adsorb the headspace for 35 minutes, then insert the GC inlet, and desorb at 250°C for 5 minutes.

[0183] The chromatographic separation uses a HP-INNOWAX capillary column (60 m x 0.25 mm x 0.25 μm), the carrier gas is high-purity helium, the flow rate is 1.0 mL / min; the temperature program is set as follows: 40°C for 3 minutes, increased to 150°C at 5°C / min, then increased to 230°C at 8°C / min and maintained for 6 minutes.

[0184] The mass spectrometry conditions are electron impact ion source, electron energy 70 eV, ion source temperature 230°C, mass scan range 30-450 amu; qualitative search based on NIST library, and internal standard method to calculate the mass concentration of each volatile component.

[0185] Experimental data:

[0186] Table 4: Analysis of the content of key volatile flavor substances under different temperature control strategies

[0187]

[0188] Conclusion analysis:

[0189] According to the data in Table 4, different temperature control strategies result in a shift in the metabolic product spectrum. Comparative Example 1 uses traditional constant temperature fermentation, with a total high-level alcohol content as high as 438.74 mg / L, in which the concentrations of isoamyl alcohol and isobutyl alcohol are at a high level, and there is a lack of aroma esters, with an ester alcohol ratio of only 0.47. This is because in the continuous medium-high temperature environment, the Ehrlich pathway metabolism of the yeast is vigorous, the deamination and decarboxylation reactions of amino acids are accelerated, a large amount of carbon source flows to the synthesis of fusel oil, resulting in a rough wine body and easy to cause discomfort after drinking.

[0190] The comparison between Example 1 and Comparative Example 4 directly reveals the core mechanism of the gradient cold shock process. Under the premise of consistent other process conditions, the total ester content of Example 1 is higher than that of Comparative Example 4 which lacks the cold shock step, especially the contents of the characteristic flavor substances isoamyl acetate and ethyl hexanoate are increased by about 91% and 117%, respectively. At the same time, the total high-level alcohol content of Example 1 is suppressed at a relatively low level of 185.28 mg / L, and the ester alcohol ratio reaches 3.31.

[0191] This difference confirms that the gradient reduction of the fermentation temperature from 22-24℃ to 10-12℃ in a short time and the maintenance of low temperature standing inhibit the key enzyme activities involved in the Ehrlich pathway, blocking the conversion of alpha-keto acids to high-level alcohols. Low temperature stress promotes the redirection of metabolic flow in yeast cells, and acyl-CoA and other ester precursors accumulate in the cells. With the subsequent temperature rising, the activated alcohol acyltransferase rapidly catalyzes the esterification reaction using these accumulated precursors, achieving the metabolic regulation goal of alcohol reduction and ester increase. Although Comparative Example 4 undergoes subsequent temperature variation, it cannot form high-concentration ester aroma due to the lack of a precursor accumulation stage at low temperature, verifying the pre-determining role of low-temperature cold shock in flavor reorganization.

[0192] Test Example 5: Sensory profile evaluation

[0193] Experimental explanation:

[0194] In this experiment, a quantitative descriptive analysis method was used to organize a sensory evaluation team of professionals to conduct multi-dimensional quantitative evaluation of the sensory quality of the finished bubble rice wine. The experiment aims to verify the contribution of interface construction, cold shock aroma generation, and gas control steps in the technical scheme to the flavor and mouthfeel of the final product from the perspective of human intuitive perception. The experimental objects include Example 1, Comparative Example 1, Comparative Example 2, Comparative Example 4, and Comparative Example 6.

[0195] The specific operation steps are as follows:

[0196] A sensory evaluation team consisting of 12 people with national level three and above wine sommelier qualifications was formed to conduct the test in a standard sensory evaluation room. The temperature in the evaluation room was controlled at 20±2℃, the relative humidity was 55-65%, and the light was neutral white.

[0197] The wine sample to be tested was pre-cooled in a 4°C refrigerator, and then transferred to a constant temperature water bath to equilibrate to 8°C. After opening the bottle cap, 30 mL of wine sample was immediately poured into a tulip-shaped wine tasting cup conforming to ISO3591 standards, and each sample cup was labeled with a randomly generated 3-digit code to eliminate psychological bias.

[0198] The evaluator completed the evaluation of aroma burst and appearance bubbles within 2 minutes after opening the bottle, and the evaluation of mouthfeel, wine body purity, and overall harmony within 5 minutes according to the sensory evaluation guidelines specified in GB / T13868 standard.

[0199] The scoring used a 10-point linear scale method, where 0 represented no perception or poor, and 10 represented strong or excellent. Each evaluator scored independently, and between each round of tasting, pure water and salt-free biscuits were used to clean the mouth, with a 5-minute interval. The final result was the arithmetic mean of the scores of the 12 evaluators. The evaluation indicators were defined as follows:

[0200] Aroma burst: the intensity and duration of fruit aroma and ester aroma released when the bottle is opened and the cup is shaken.

[0201] Mouthfeel: the micro-stimulation and delicacy of bubble rupture when the wine enters the mouth, rather than a rough tingling sensation.

[0202] Wine body purity: whether there are off-flavors such as oxidation (paperboard / rotten apple flavor), sulfur flavor, or yeast autolysis flavor.

[0203] Overall harmony: the balance of sweetness and acidity, the fusion of bubbles and wine body, and the pleasantness of aftertaste.

[0204] Experimental data:

[0205] Table 5: Sensory profile score statistics of finished wine under different process conditions

[0206]

[0207] Conclusion analysis:

[0208] According to the data in Table 5, each experimental group showed differences in different sensory dimensions, which directly corresponded to the mechanism contribution of different technical modules of the invention.

[0209] Example 1 obtained the highest score in all dimensions, especially the overall harmony reached 9.03 points, indicating that the coupling of each process link produced a good superposition effect.

[0210] Regarding the killing mouthfeel index, Comparative Example 2 only obtained 3.62 points, lower than 8.85 points of Example 1. This data difference proves the actual sensory effect of the physical nucleation mechanism: missing enzyme, fiber interface construction, the system cannot provide enough heterogeneous nucleation sites, resulting in carbon dioxide gas unable to combine in the form of delicate microbubbles in the wine liquid, lacking a soft micro-stimulating sensation after entry, and the mouthfeel is close to still wine or only a rough large bubble sensation.

[0211] Regarding the aroma explosion index, Comparative Example 4 scored 4.88 points, much lower than 8.92 points of Example 1. Although Comparative Example 4 retains the interface construction, due to the lack of gradient cold shock step, the yeast metabolism fails to shift to the esterification pathway, resulting in a lack of isoamyl acetate and other characteristic aroma substances. This shows that a simple bubble structure cannot make up for the sensory defects caused by the lack of flavor substances.

[0212] Regarding the wine body purity index, Comparative Example 6 showed a cliff-like drop, only 3.92 points, and the evaluator's remarks frequently appeared oxidized taste, bitterness and other descriptions. This verifies the key role of nitrogen gas stripping process in the redox potential control. If only oxygen pulse is performed without subsequent nitrogen gas replacement, the residual dissolved oxygen and activated acetaldehyde dehydrogenase pathway will lead to the accumulation of acetaldehyde, producing a pungent solvent taste and stale oxidation taste, seriously damaging the purity of the wine body.

[0213] In summary, the high score of Example 1 is not a breakthrough of a single technology, but the result of a three-dimensional system engineering based on interface physical modification to solve bubble structure, metabolic flow redirection to solve endogenous aroma, and gas replacement to solve purity. The lack of any link will lead to the collapse of the product in a certain key sensory dimension, and cannot achieve the overall improvement of the flavor and mouthfeel of bubble rice wine.

Claims

1. A process for upgrading the flavor of a sparkling rice wine based on segmented temperature-controlled fermentation, characterized by, The method comprises the following steps: 100 parts by weight of fine glutinous rice is steamed and gelatinized, cooled, and then added with 0.18-0.30 parts by weight of an interface building component at 55-60°C for enzyme modification, followed by cooling and adding 0.4-0.6 parts by weight of saccharifying koji for saccharification; The interface building component comprises superfine citrus fiber and pectinase, and a solid-liquid interface of stable bubbles is built in the fermentation liquor through enzyme reaction; 150-180 parts by weight of brewing water is added to the saccharified mash, and then 0.005-0.01 parts by weight of an anti-stress regulator and 0.01-0.03 parts by weight of a composite yeast inoculum are added after adjusting the pH value, and then proliferation fermentation is carried out at 22-24°C; The fermentation mash is cooled to 10-12°C, and then accumulated ester precursor substances are accumulated under the condition of low-temperature static fermentation; The mash is warmed, sterile air is introduced for oxygen pulse during the warming process, and then nitrogen gas is introduced for stripping treatment; The tank is sealed, and then the temperature is continuously increased to 16-18°C, the pressure is increased naturally by using the gas produced by yeast metabolism, and the pressure is maintained to complete bubble stabilization.

2. A process for upgrading the flavor of a sparkling rice wine based on segmented temperature-controlled fermentation according to claim 1, characterized in that, The interface building component is an enzyme and fiber composite powder prepared by mixing superfine citrus fiber and pectinase at a weight ratio of (3-7):

1. The insoluble cellulose content of the superfine citrus fiber is 45%-50%.

3. A process for upgrading the flavor of a sparkling rice wine based on segmented temperature-controlled fermentation according to claim 1, characterized in that, The composite yeast inoculum is composed of ester-producing Saccharomyces cerevisiae and psychrotrophic Brettanomyces, and the cell number ratio of the two is (4-5):

1. The anti-stress regulator is food-grade zinc sulfate heptahydrate, and the addition amount of the anti-stress regulator is such that the zinc ion concentration in the fermentation system is 5.0-8.0 mg / L.

4. A process for upgrading the flavor of a sparkling rice wine based on segmented temperature-controlled fermentation according to claim 1, characterized in that, The pH value is adjusted by using a pH regulator selected from citric acid, sodium citrate buffer, and lactic acid, and the initial pH value of fermentation is adjusted to 5.5-5.

8.

5. The process as claimed in claim 1, wherein the process is based on the segmented temperature controlled fermentation of the bubble rice wine flavor. The interface building component is added when the temperature of the glutinous rice is reduced to 55-60°C, and the temperature is maintained for 25-35 minutes for reaction. The addition amount of the superfine citrus fiber is 0.15%-0.25% of the mass of the dry glutinous rice.

6. A process for upgrading the flavor of a sparkling rice wine based on segmented temperature-controlled fermentation according to claim 1, characterized in that, In the step of cooling to 10-12°C, the temperature is controlled to decrease at a rate of 4-6°C / h from 22-24°C to 10-12°C, and then the fermentation is carried out at the current low temperature for 48-60 hours.

7. A process for upgrading the flavor of a sparkling rice wine based on segmented temperature-controlled fermentation according to claim 1, characterized in that, The specific operation of the heat and oxygen double pulse regulation comprises the following steps: When the temperature of the mash is increased to 12.5-13.0°C, sterile air is introduced to maintain the dissolved oxygen concentration at 1.5-2.5 mg / L, and the process is continued for 15-20 minutes; Then, high-purity nitrogen gas is immediately introduced, and the gas flow rate is 0.1-0.2vvm until the dissolved oxygen concentration is reduced to below 0.1 mg / L.

8. A process for upgrading the flavor of a sparkling rice wine based on segmented temperature-controlled fermentation according to claim 1, characterized in that, In the step of continuously increasing the temperature of the sealed tank, the temperature is controlled to increase at a rate of 0.4-0.6°C / h, and the final temperature is 16-18°C; The absolute pressure in the tank is controlled to be 0.15-0.20 MPa, and the process is maintained for 48-55 hours.

9. A process for upgrading the flavor of a sparkling rice wine based on segmented temperature-controlled fermentation according to claim 1, characterized in that, After the bubble stabilization is completed, the fermentation liquor is cooled to 0-2°C, and then the cross-flow filtration is carried out under the condition of constant pressure by using a membrane with a pore size of 0.8-1.2 μm, and the filtered wine is subjected to low-temperature filling.

10. A process for upgrading the flavor of a sparkling rice wine based on segmented temperature-controlled fermentation according to claim 2, characterized in that, The enzyme and the preparation method of the fiber compound powder are as follows: the superfine citrus fiber and the pectinase are placed in a V-shaped mixing machine, and mixed for 25-35 minutes under the condition that the temperature is 18-22 DEG C and the relative humidity of the environment is 30%-40%, until the variation coefficient of the uniformity of the mixture is less than 5%.

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