Abnormal treatment of beer fermentation process

1. Fermentation broth agitation (resulting in slow liquid clarification, difficult filtration and poor quality)

Cause: Improper opening of cooling jacket caused the deviation between the upper temperature and the process curve 1.5 ~ 4℃, and the high temperature in the middle of the tank caused strong convection of fermentation broth. In addition, pressure instability and sharp rise and fall can also cause tumbling.

Solution: Check whether the instrument is normal; Strictly control the cooling temperature to avoid excessive temperature of upper black liquor; Keep the pressure in the tank stable.

2. The fermenter is frozen.

When the temperature in the lower part of the tank deviates from the process curve by about 2℃, the temperature in the tank will reach the freezing point of beer during storage (-1.8 ~ 2.3℃), which may lead to freezing near the cooling zone.

The empirical formula for calculating the freezing point temperature of beer is:

G =-A×0.42+P×0.04+0.02

The alcohol content in A- beer is m/m%.

P- original wort concentration m/m%

G- freezing point℃

Causes of icing: instrument failure, improper selection of temperature parameters, improper installation position and depth of thermal resistance, poor instrument accuracy, improper operation, etc.

Solution: check the errors of temperature measuring elements and instruments, especially check whether the platinum resistor leaks. If it leaks, it should be sealed or baked and replaced with paraffin. Select the appropriate temperature measuring point position and thermal resistance insertion depth; Strengthen process management and discharge yeast in time; The temperature of refrigerant liquid should be controlled at -2.5 ~-4℃, and refrigerant liquid at -8℃ cannot be used.

3. Yeast autolysis

Reason: When the temperature difference between the lower part and the middle and lower part of the tank is greater than 1.5 ~ 5℃, yeast precipitation and yeast autolysis will be difficult. If the temperature is too high (16 ~ 18℃) and the yeast mud at the bottom of the tank is kept for too long, it will also cause yeast autolysis, produce yeast smell, and sometimes make beer turbid after sterilization.

Solution: Check whether the instrument is normal; Discharging yeast mud in time; The temperature of refrigerant is kept at -4℃, and the upper, middle and lower temperatures of wine during storage are kept at-1 ~ 1℃.

4. Looking up after drinking beer

Reason: When the contents of higher alcohols, isobutanol and isoamyl alcohol in beer exceed 120mg/L, 10mg/L and 50mg/L, respectively, drinking beer will cause the phenomenon of head-up.

Solution: Select yeast species with low yield of higher alcohols; Increasing the amount of yeast properly to reduce the proliferation of yeast, the appropriate number of yeast cells is 15× 10 cells/ml; Control the α -amino nitrogen content of 12 P wort at about180 200 mg/L; Control the dissolved oxygen content in wort at 8 ~ 65438 00 mg/L; Control fermentation temperature and tank pressure.

5. Diacetyl reduction is difficult.

After fermentation, the content of diacetyl is too high to meet the requirements.

The reasons for this phenomenon are as follows: the content of α -amino nitrogen in wort is low, and more α -acetolactic acid is produced by metabolism, resulting in a high peak value of diacetyl, which cannot be reduced; Using high-temperature rapid fermentation, the content of fermentable sugar in wort is high, and yeast proliferation is great, which is beneficial to the formation of diacetyl. In the late stage of main fermentation, the yeast settled prematurely, and the number of yeast suspended in the fermentation broth was too small, so the diacetyl reduction ability was poor. The yeast used is aging or its ability to reduce diacetyl is poor.

Solution: control the content of α -amino nitrogen in wort (160 ~ 200mg/L) to avoid being too high or too low; Appropriately increase yeast inoculation amount and full tank temperature, and appropriately increase diacetyl reduction temperature; The fermentation temperature should not be too high, and after heating, pressure fermentation should be used to inhibit the proliferation of yeast. After the main fermentation, the cooling rate should not be too fast; Adopting a strain with strong diacetyl reducing ability; Adding high sparkling wine to accelerate the reduction of diacetyl; Washing with carbon dioxide to remove diacetyl; After cooling, filter with wine in other cans.

6. Diacetyl rebound

The phenomenon that diacetyl is qualified after fermentation, and the diacetyl content increases after low temperature storage or filtration, or after sterilization is called diacetyl recovery.

The main reasons for diacetyl recovery are: the high residue of diacetyl precursor in beer, and the excessive recovery of diacetyl after sterilization caused by oxygen inhalation after drinking; In the late stage of fermentation, bacterial infection caused diacetyl to rise again; After filtration and oxygen inhalation, the yeast produces α -acetolactic acid, and the diacetyl content increases after oxidation.

Solution: Try to reduce oxygen absorption when filtering; The filtered sake should not be stored for a long time, and it is not suitable to stay overnight without enough cans. Adding antioxidants such as ascorbic acid or glucose oxidase to sake to eliminate dissolved oxygen in wine; The filling machine should use carbon dioxide back pressure; When filling wine, use sake or deoxygenated water to induce foam, so as to completely eliminate bottleneck air and avoid oxygen absorption in beer.

7. Fermentation stop phenomenon

The suspension of fermentation of fermentation broth is called not lowering blood sugar.

The reasons for this phenomenon are: insufficient nutrition in wort, too high oligosaccharide content, insufficient α -amino nitrogen, too high or too low acidity; Yeast has strong cohesion, which leads to early flocculation and precipitation; Yeast degenerates and mutates, resulting in no hypoglycemic effect; Spontaneous mutation of yeast leads to respiratory defects of yeast.

Solution: If it is caused by early flocculation and precipitation due to the strong cohesiveness of yeast. The fermentation temperature can be adjusted by increasing the ventilation rate of wort, and then the temperature can be lowered when the sugar content drops to near the final fermentation degree to prolong the high temperature period. But it will improve the cohesiveness of yeast, and it is best to isolate yeast strains with weak cohesiveness to solve this phenomenon. If it is due to yeast degradation mutation, it will not lower blood sugar. It can be solved by replacing new yeast species. If it is caused by spontaneous mutation of yeast, it will produce respiratory defect yeast. The original strain can be re-cultured or replaced. In addition, in the process of wort preparation, it is necessary to strengthen the hydrolysis of protein, appropriately reduce the decomposition temperature of protein and prolong the decomposition time of protein; When saccharifying, it is necessary to properly adjust the saccharifying temperature, strengthen the hydrolysis in the low temperature section, ensure enough saccharifying time, and adjust the PH value of the mash.

Four, other beer fermentation technology

(A) pure draft beer brewing technology

Draft beer is strictly sterilized (non-thermal sterilization) to ensure that there is no live yeast or other microorganisms in the wine, and the shelf life is six months to one year, also known as cold sterilized beer. Draft beer is a new beer product gradually developed in recent decades, and its goal is to make beer taste fresh, pure and refreshing. Due to the continuous improvement of cold sterilization technology, the output of draft beer is increasing day by day, which has become one of the hot spots in the beer industry market competition. It can be predicted that in the next few years, draft beer will occupy an important position in the beer sales market in China.

Quality requirements of draft beer: it has the same biological stability and abiotic stability as cooked beer; Keep the freshness (flavor stability) of beer for a long time; It has good flavor and taste, as well as good wine appearance and foam performance; Meet the requirements of specified physical and chemical indexes. That is, the quality requirements of draft beer are the same as those of cooked beer except that thermal sterilization is not used.

The main problem in the production of draft beer is that protease A still exists in beer without thermal sterilization, which has a great influence on beer foam and leads to poor foam retention.

Determination standard of draft beer: determination of sucrose invertase activity in beer. Generally, the activity of sucrose invertase in beer after pasteurization or instant sterilization is destroyed. By measuring the activity of sucrose invertase, it can be judged whether it is pure draft beer.

1. Production mode of draft beer:

The production of draft beer must be kept sterile or controlled in the whole production process, and finally enter the sterilization and filtration combined system for sterilization and filtration. Comprises a composite deep sterilization filtration system and a membrane sterilization filtration system. After sterilization and filtration, yeast and all other microbial vegetative cells should be basically removed (sterilization and filtration LRV≥7) to ensure the biological stability of draft beer.

(1) Microbial inhibition method Adding inorganic inhibitors or organic inhibitors (preservatives) to liquor can avoid beer spoilage by inhibiting the reproduction and metabolism of microorganisms. Commonly used disinfectants are benzoic acid, sorbic acid, kojic acid, mycophenolate mofetil, nisin and so on.

(2) Ultraviolet sterilization method uses ultraviolet rays to kill microorganisms and control a small amount of microorganisms in beer. Because the sterilization effect of ultraviolet rays is not ideal and may affect the taste of beer, it has not been adopted at present.

(3) Aseptic filtration is a commonly used cold sterilization method at present. The beer filtered by diatomite filter and fine filter enters the sterilization and filtration combined system for sterilization and filtration. Comprises a composite deep sterilization filtration system and a membrane sterilization filtration system. After sterilization and filtration, yeast and all other microbial vegetative cells should be basically removed (sterilization and filtration LRV≥7) to ensure the biological stability of draft beer.

2. The basic requirements of draft beer production:

(1) The key to purebred brewing-the production of draft beer by beer yeast is an organic combination of purebred brewing and effective control of later pollution. The existence of any miscellaneous bacteria will affect the quality of beer.

(2) Choose fermented and post-cooked beer with good wine base and good quality (including flavor, foam, abiotic stability and meeting the requirements of physical and chemical indexes). In production, we should control raw materials, select strains and strictly control production technology and operation.

(3) Ensuring reliable aseptic production conditions The production of draft beer is the result of effective control of miscellaneous bacteria in the production process, not the result of various means of treatment. Strict control of miscellaneous bacteria in the production process is the key to draft beer production, and aseptic filtration and aseptic filling are the auxiliary means of production. Therefore, the whole process of beer production should be free of mixed bacteria pollution or basically free of mixed bacteria pollution to ensure the quality of pure draft beer and reduce the workload of post-treatment.

(4) On the basis of strictly controlling the microbial pollution in the previous process, the aseptic filtration for producing pure draft beer should meet the following requirements: the effectiveness of aseptic filtration, the removal rate of any microorganisms should meet the requirements, and the quality requirements such as beer taste and foam will not be affected; To choose a reasonable aseptic filtration combination, it is generally required that the combination should be carried out in the order of deep filtration, surface filtration and membrane filtration. The pore size is selected as follows: deep filtration 1 ~ 3 micron, surface filtration 0.8 ~ 1 micron and membrane filtration 0.45 ~ 0.65 micron. Configure two groups of filtration combinations to ensure normal production; Have independent CIP and membrane regeneration system;

(5) When packaging draft beer, the following basic requirements should be met: the cleaning system of packaging containers (including bottles, cans and draft beer barrels) should be clean and sterile; For the filling workshop, the filling machine can be placed in a sealed aseptic room, and the indoor air can be effectively filtered to maintain the indoor positive pressure, which is about 0.03 ~ 0.05 kPa. For the conveying chain for conveying beer bottles, the chain lubricant with disinfection function should be used in the part before the unfilled beer is sealed, and the conveying chain in front of the filling machine should be provided with a continuous cleaning device to ensure the hygiene of the whole conveying chain. The bottle washer in the draft beer filling line should be single-ended to prevent the dirty bottle at the bottle inlet end from polluting the clean bottle at the bottle outlet end; In the process of conveying the washed beer bottles to the filling machine, there should be a closed protective cover to avoid the pollution of dust and flying insects.

3. Microbial management in draft beer production

Preparation of (1) Brewing Sterile Water

Treatment process:

Deep well water → softening treatment → sand filtration → activated carbon filtration → particle capture filtration → pre-filtration → sterilization filtration.

For water with high hardness, softening treatment should be carried out first, and then membrane filtration treatment should be carried out after removing large particles of impurities. The water sterilization filter should be steam sterilized before use, and the water network for production water should be cleaned and disinfected regularly. Microbial control indicators of sterile water: total number of bacteria ≤ 10/100ml, yeast 0/100ml, anaerobic bacteria 0/100ml.

(2) Preparation of sterile air

Sterile air is used for oxygenation of cold wort and yeast expansion. Improper aseptic air filtration will affect the microbial control in draft beer production, so the management of aseptic air filtration system must be strengthened. The preparation process of sterile air is as follows:

Compressed air → oil removal, water removal and impurity removal → pre-filtration → sterilization filtration → sterilization filtration in key stations → sterile air.

Microbial control index of aseptic air: the total number of bacteria ≤3/10 minute, yeast 0/10 minute, anaerobic bacteria 0/10 minute.

(3) Preparation of sterile CO2

CO2 is used in the process of beer brewing, such as the addition of sake CO2, the preparation of deoxygenated water, the back pressure of sake tank, etc. In the production of draft beer, CO2 should also be sterilized, and the CO2 recovery pipeline should be cleaned regularly with CIP, and the gas sterilization filter should be disinfected with steam before each use. The preparation process of sterile CO2 is as follows:

CO2 Liquefying Tank → Heating Gasification → Pre-filter → Sterilizing Filter → Distribution Point Sterilizing Filter → Sterile CO2 Sterile CO2 Microbiological Control Indicators: Total bacteria ≤3/10 min, yeast 0/10 min, anaerobic bacteria 0/10 min.

(4) steam disinfection treatment

The purpose of treatment is to remove the particles brought by steam, prevent the sterilization filter from being damaged or blocked, and prolong the service life of the filter. Steam filtration generally adopts stainless steel microporous filter element, and the filtration accuracy is 65438 0.0 μ m. ..

(5) Microbial control in filtration operation

(1) Avoiding the pollution of fermentation broth to miscellaneous bacteria is the basis of pure draft beer production.

(2) Before filtration, CIP cleaning shall be carried out on the wine conveying pipeline, buffer tank, filter, diatomite (or perlite) adding tank and sake tank.

③ The sampling valves of the filtration system and sake tank should be disassembled and cleaned regularly, and cleaned strictly before each operation.

④ Movable elbows, pipe joints, hoses, sampling valves and tools should be soaked with disinfectant when not in use.

⑤ Diatomite adding room should be separated independently, and ultraviolet lamp should be installed for regular sterilization.

⑥ Clean the filtration system with 0. 1% hot acid after each operation, and clean the filtration system with 2.0% hot alkali every week.

All landowners sake requirements:

Turbidity < 0.5EBC unit; β -glucan

(6) aseptic filtration of sake

Sterile filtration is carried out by a 0.45μm film filter installed in front of the filling and sealing machine. The membrane filter should have a highly sensitive membrane integrity detection system. The hot and cold water used by the membrane filter should be pre-filtered by 20μm to treat large particles, and then used by the membrane filter.

(7) aseptic filling

① The filling room should meet the cleanliness requirement of 300,000 class, and the design, construction and disinfection of clean room can refer to GMP standard of pharmaceutical industry.

(2) Clean room staff shall wear clean clothes, and the number shall not exceed 4. Avoid frequent personnel access, and strictly disinfect personnel access.

(3) draft beer bottles should use new bottles with good sanitary conditions (such as tray bottles packed with film); Sterile bottle caps suitable for draft beer should be adopted, and the bottle cap storage hopper should be equipped with ultraviolet lamp for disinfection.

(4) The last washing water of the bottle washer is used for hot water bottle washing. The bottle conveying system from the outlet end of the bottle washer to the inlet of the clean room should be equipped with an isolation cover and an ultraviolet lamp, and the outlet end should be thermally disinfected at 1 hour; It is necessary to use chain lubricant containing antibacterial ingredients and softener with water resistance, acid and alkali resistance, and disinfect the conveyor chain plate, water receiving plate, bottle fence, glass cover and chain underframe.

⑤ Before using the filling and capping machine, clean the surface of the equipment and the place where the bottle enters and exits, and turn on the ultraviolet lamp for air disinfection in advance. Regularly pickling and filling the capping machine every month to prevent the machine from scaling.

4. The production process of draft beer should ensure reliable aseptic conditions.

Strictly speaking, the production of draft beer is the result of effectively controlling the pollution of miscellaneous bacteria in the production process, rather than the result of various treatment methods, so it cannot rely solely on terminal filtration and corresponding other treatments. That is to say, in the production process of draft beer, the most important thing is to strictly control the pollution of miscellaneous bacteria in the production process, and the final aseptic filtration and aseptic filling are only auxiliary means to ensure and improve the quality of draft beer. Therefore, it is required that there should be no or almost no mixed bacteria pollution in the whole process of beer production. In the words of Siping Jinshibai Beer Group, the key to producing draft beer is to create a pure environment. In order to ensure the quality of draft beer and reduce the workload of aseptic filtration and aseptic packaging in the later stage, the number of miscellaneous bacteria is required to be less than 10 /ml.

(1) Types of mixed bacteria pollution in beer production:

① Primary pollution and secondary pollution:

Primary pollution refers to the microbial contact pollution that occurs in the process of beer production from the time when it can be polluted, which is harmful. Secondary pollution refers to the contact pollution of beer after aseptic treatment, which mainly occurs in the process of sake and packaging. Secondary pollution is the content that must be strictly controlled in the production of draft beer.

② Cross pollution and cumulative pollution:

Cross-contamination means that the production equipment, tools, yeast adding facilities used by * * * are contaminated by miscellaneous bacteria, and the disinfection and sterilization are insufficient, resulting in mutual contamination. Among them, yeast pollution is more harmful.

Cumulative pollution refers to the continuous pollution in each process of beer production, resulting in the accumulation of pollution levels. This kind of pollution is serious, which is the most harmful to beer quality.

(3) Direct pollution and secondary pollution:

Direct pollution refers to the pollution of raw and auxiliary materials, additives, equipment, pipelines, gas sources and water sources. They are in direct contact with the product. Secondary pollutants refer to the pollution caused by direct contact with products, such as human body and environment.

(2) To produce draft beer, we should also do the following work:

(1) First of all, we should do a good job in aseptic filtration, disinfection and sterilization of materials such as air source and water source that are in direct contact with the product to prevent direct pollution and primary pollution of the product.

Secondly, the wort preparation, beer fermentation, aseptic filtration and packaging are equipped with CIP and SIP systems respectively, so as not to use them as much as possible.

③ The inner walls of containers, pipes and valves used in production should be polished and smooth. The Ra of the polished inner wall should be not less than 0.8 micron, and should reach 0.5 micron as much as possible.

④ The whole beer production process should be carried out under closed positive pressure, and good CIP washing and effective SIP disinfection can be achieved.

⑤ All kinds of raw materials, materials and preparations used in cold beer products, including adding yeast, should be strictly controlled under aseptic conditions to ensure that they are not contaminated by miscellaneous bacteria.

⑥ It is necessary to improve the microbial detection means, determine the corresponding microbial detection points and detection systems, use advanced detection methods and instruments, and conduct effective microbial monitoring throughout the process to ensure the conditions of aseptic production.

(2) Production technology of wheat beer

Wheat beer is a special type of beer brewed with wheat malt as the main raw material, supplemented by some malt and auxiliary materials (rice, etc.). ) and hops. It is characterized by refreshing and soft taste, high alcohol content and good foam performance, similar to foreign white beer or fermented beer.

1. Production form of wheat beer

Wheat beer has three production forms:

(1) Above fermentation belongs to the traditional production method of ale beer. Using malt and malt as raw materials, wort was made according to a certain saccharification process, inoculated with top yeast and fermented at a higher temperature. After fermentation, yeast is recovered by skimming, and it is made after proper time ripening and wine storage. It has the typical taste of malt beer.

(2) The saccharification operation of mixed fermentation type is the same as that of upper fermentation type, but two kinds of yeast (upper yeast and lower yeast) are used for fermentation at the same time, but the time of yeast addition is different, that is, the yeast is first fermented with the upper yeast at a higher temperature, and after reaching a certain degree of fermentation, the yeast is recovered by the above fermentation method, and then transferred to the wine storage tank. Add the following yeast to the wine storage tank for fermentation and after-ripening treatment for a proper time.

(3) The stage fermentation type is similar to the mixed fermentation type, that is, upper yeast is added to wheat malt and wort made of malt for upper fermentation at a higher temperature, after fermentation, the upper yeast is separated by a yeast centrifuge, then the upper yeast is instantly sterilized to remove it, and it is quickly cooled to the fermentation temperature of the lower yeast, and wort and lower yeast are added for second fermentation and post-ripening. Foreign white beer is mainly produced by the above method.

2. Selection of malt

Generally, wheat with low protein content, low chroma and low viscosity is selected to make wheat malt.

The solubility of (1) wheat malt is generally lower than that of barley malt, and there is a big difference between coarse and fine powder extracts, with a low Coulbach value and insufficient protein solubility. Therefore, protein decomposition should be strengthened during saccharification.

(2) Wheat malt has no rough skin, and the waterless leaching rate is about 5% higher than barley malt.

(3) The content of anthocyanins in wheat malt is low, and the temperature of spent grains washing can be raised to 80℃ (the spent grains washing water is acidified first).

(4) The content of maltose protein is high, and the brewed beer has good foam performance, and the foam is rich and lasting.

(5) Due to insufficient cell lysis, the content of hemicellulose such as β -glucan in malt is high, and the viscosity of wort is high, which easily makes wort filtration difficult. Appropriate amount of β -glucanase and pentosanase should be added during saccharification to reduce the viscosity of wort and speed up filtration.

(6) The high content of protein in malt will lead to the difficulty of wort filtration and poor abiotic stability of beer. Therefore, wheat varieties with low protein content should be selected as far as possible to prepare wheat malt.

(7) The wort filter press should be used for wort filtration as much as possible.

(8) Traditional wheat beer has obvious ester flavor and sour taste, but the flavor of wheat beer brewed by low-temperature fermentation with subsequent yeast has little change.

(9) Adding silica gel before the filtration of malt beer can improve the clarity of beer and make it easy to filter.

4. Process requirements

(1) The decomposed nitrogen content of protein wheat malt is higher than that of barley malt, and the solubility of wheat malt is lower than that of barley malt, and the proportion of powdery particles is slightly lower (more than 80%), and the Kurbach value is less than 40%. Therefore, the decomposition of protein must be strengthened.

(2) The turbidity of malt beer is high. When wort is boiled, wort clarifier (carrageenan) can be added, and the dosage is 20 ~ 30 mg/ 100 L wort, so as to improve wort clarity and speed up wort filtration.

(3) Strengthen wort boiling, the boiling intensity should reach 9 ~ 10%, and the boiling pH should be 5.2 ~ 5.4. Appropriate amount of CaCl2 can also be added, which is beneficial to the flocculation and precipitation of protein.

(4) adopting low-temperature fermentation technology, discharging yeast in time after boosting the pressure to reduce yeast autolysis, and discharging yeast every two days or so after entering the wine storage period. The storage time of wine below 0℃ is longer, which is beneficial to the export of polyphenols from protein and protein to the west.

(5) When filtering the wine, add protease, such as enzyme clear or papain, to further decompose protein, and the amount to be added should be determined according to small experiments. Adding too much will weaken the taste of beer, make the foam performance worse, and at the same time make the beer turbid (because it is also protein).

(6) Before filtration, the temperature of the fermentation broth was quickly reduced to below-65438 0℃ to promote protein precipitation.

(7) Before filtering, a proper amount of edible tannin can be added to precipitate protein, and the adding amount is generally about 20mg/ 100L beer, which is beneficial to prevent beer turbidity and avoid the difficulty of beer filtering.

(3) Production technology of low-alcohol and alcohol-free beer

Low-alcohol beer refers to special beer with lower alcohol volume fraction than ordinary beer, such as non-alcohol beer and low-calorie beer. Alcohol-free beer refers to special beer with alcohol content below 0.5% after normal beer production process. Alcohol-free beer is very suitable for social occasions because of its low alcohol content, and also suitable for some people who are not suitable for drinking, such as women, drivers, athletes, teenagers, children, alcoholics and other consumers. It is understood that the alcohol-free beer first introduced in Switzerland has been produced in the United States, Germany, Britain, Japan and other countries, and has made great progress. Yanjing and other domestic beer producers have begun to use low-temperature vacuum distillation technology to produce alcohol-free beer.

The key to producing low-alcohol beer is to require low alcohol content, but the unique flavor of beer should not be less, and other quality characteristics should also be guaranteed.

The production technology of low-alcohol beer can be roughly divided into two categories:

One is to control the amount of alcohol produced in beer fermentation within the required standard range, such as Saccharomyces cerevisiae method, Pasteur patent method, high temperature saccharification method and so on. At present, alcohol-free beer can be produced by inducing mutant yeast, which can convert alcohol into esters or organic acids. ) or alcohol is basically not produced in the fermentation process, which can make wort ferment normally without producing bad flavor and harmful components. The volume fraction of alcohol in fermented beer is ≤0.5%.

The other is to remove alcohol from normal fermented beer by various means, such as vacuum evaporation, reverse osmosis, dialysis and so on.

The advantages of dealcoholization are:

(1) The dealcoholization amount can be controlled at will, and alcohol-free beer can be produced.

(2) The saccharification and fermentation process does not need to be changed, and only post-fermentation treatment is needed.

The disadvantages of alcohol removal method are:

(1) Need to invest a lot of money to buy alcohol removal equipment.

(2) Additional treatment costs and time are needed.

(3) During the processing, beer flavor substances will be lost.

(4) Improper handling can easily lead to secondary pollution.

The advantages of limited fermentation method are:

(1) does not require additional equipment investment.

(2) The production process is simple and the cost is low.

(3) Less flavor loss.

The disadvantages of the restrictive fermentation method are:

(1) The saccharification or fermentation process changes, which requires high process control.

(2) Improper control will affect the taste and stability of beer.

At present, both production processes are in use. It is more economical and practical to produce low-alcohol beer by limited fermentation, and the production cost of low-temperature vacuum distillation is higher. The application of membrane technology opens up a new way for the production of alcohol-free beer with high efficiency, energy saving and environmental protection.

1. Brief introduction to the method of producing low-alcohol beer by restricted fermentation;

(1) dilution method

Ordinary wort can be diluted to a lower concentration for fermentation, or diluted to the required concentration after fermentation to produce low-alcohol beer. The disadvantage of this method is that if the dilution ratio is too low, the alcohol content in beer can't reach the required value. When the dilution ratio is too high, beer flavor substances are diluted at the same time, which leads to the beer taste becoming weak.

(2) Low temperature leaching saccharification method

After malt is crushed, it is soaked in hot water below 60℃. Because the starch in malt will not gelatinize and decompose under this condition, it will not produce fermentable sugar, and the leaching solution only contains a small amount of sugar brought by malt. The fermentation of wort treated by this saccharification method can produce lower alcohol content.

(3) Method of stopping fermentation

When the beer is fermented to the required alcohol content, the temperature is quickly lowered, and at the same time, the yeast is separated from the fermentation broth to stop the fermentation. The beer produced by this process is sweet, and it is difficult to completely reduce diacetyl.

(4) Pasteur's patent law

This technology skillfully combines high concentration fermentation with low concentration fermentation, which not only overcomes the shortcomings of low-alcohol beer produced by low concentration fermentation, but also overcomes the shortcomings of high concentration fermentation. The low-alcohol beer produced by this method has good flavor, simple production technology and easy control. This technology can produce low-alcohol beer with an alcohol content of 0.9% ~ 2.4%.

(5) Waste grains method

The saccharified waste grains were soaked, decomposed by acid and cooked to produce low-concentration wort. In order to ensure the proper flavor of wort, 40% ~ 60% wort produced by low temperature leaching can also be added. This wort fermentation produces low alcohol content. The disadvantage of this process is its complicated operation.

(6) Saccharomyces cerevisiae method

Ordinary wort is fermented by special Saccharomyces rouxii. Because this yeast can only ferment fructose, glucose and sucrose, which account for about 0/5% of the total sugar content of wort/kloc-0, but not maltose, it can only produce a small amount of alcohol. But the disadvantage is that the low-alcohol beer produced by this process contains a lot of maltose, which makes the beer sweet and has poor biological stability.

(7) High temperature saccharification method

By adopting higher saccharification temperature, the process of starch decomposition by β -amylase was skipped, and a large amount of maltose was avoided, but it was completely liquefied to prevent excessive dextrin residue from affecting the stability of beer. The wort produced by this process can only ferment 25% ~ 30% sugar under normal conditions, and the alcohol content can be completely controlled below 65438 0.5%. The key of this process is the precise control of saccharification. Proper saccharification process control can completely ensure that beer has proper fermentation degree and good beer flavor and stability. The disadvantage is that the saccharification operation requires higher requirements.

(8) immobilized yeast fermentation method

Using a specific yeast fixed on a carrier, the wort slowly flows through the immobilized yeast column within 5 ~ 20 hours, and the formation of alcohol is accurately monitored and adjusted by adjusting the low temperature and flow rate to produce alcohol-free beer that meets the requirements. While controlling the formation of alcohol, it can still produce fermentation by-products and flavor substances. The alcohol-free beer produced meets the quality requirements, with low alcohol loss, environmental protection and good development potential.

2. Brief introduction of alcohol-free beer by dealcoholization

(1) low-temperature vacuum evaporation (distillation) method

In this method, ethanol in normal fermented beer is evaporated by vacuum evaporation or distillation, and a proper amount of water is added to meet the quality requirements of alcohol-free beer. Alcohol can also be evaporated or distilled, and then mixed with a certain amount of low-alcohol beer to make the flavor of the mixed beer close to that of normal beer.

This method requires distillation at low pressure (4 ~ 20kPa absolute pressure) and low temperature (30 ~ 55℃) to keep the volume fraction of alcohol below 0.5%. The methods used include vacuum distillation, vacuum evaporation and vacuum centrifugal evaporation. Among them, evaporation method has better effect.

(2) Membrane separation method

Membrane separation method is to make beer flow through a membrane made of organic or inorganic materials to achieve the purpose of removing alcohol. Commonly used methods are reverse osmosis and dialysis.

Alcohol removal by reverse osmosis can be divided into three stages: concentration, secondary filtration and replenishment. Concentration stage: 2.2L of exudate was produced per 100 liter of beer by membrane filtration, and the alcohol content and concentration of residual beer increased. Secondary filtration stage: completely desalted water is used to supplement the leachate separated by roasting in beer until the alcohol content in the concentrated solution reaches the required level. Supplementary stage: add water to the concentrated solution to the original beer, and the alcohol content will also drop below 0.5%. At the same time, it is necessary to supplement CO2 to beer, because the CO2 content in beer is very low through reverse osmosis and water supplement.

The membrane of dialysis method is made of thin-walled hollow fiber, and its pore size is very small. Alcohol in beer permeates through the membrane to the other side of the membrane, while macromolecular substances in beer are trapped. With the dialysis process, the alcohol content in exudate gradually increased, and the alcohol content in beer gradually decreased. When the alcohol in the exudate is slowly removed by continuous vacuum distillation, the alcohol in the beer can meet the requirements.