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Gases in Breweries
C H A P T E R
7.4 Gases in Breweries Philippe Girardon Air Liquide, Paris, France
Among the different steps of this process, gases play the following role:
7.4.1 MALTING This step lasts for 8–9 days and can be done outside the beer manufacturing plant by different specialized companies linked to the grain business. After being cleaned, calibrated, and sorted, the barley grains are soaked in a tank containing pure deionized water. This leads to germination of the grains. Normal oxygenated water with air is sufficient. The oxygenation of this water with pure oxygen can accelerate the start of the germination process, which takes place at a temperature of about 25°C. However, references are not frequent. The germination is stopped by a flow of hot air (70–85°C). Its intensity influences both the flavor and the color of the beer. From this point on, barley is now referred to as malt. Sprouts are separated from the grains before storage in a silo.
7.4.2 BREWING The brewing process lasts for about 10 hours. Malt is ground first in a mill. The malt flour is mixed with water and becomes a slurry. Other
Gases in Agro-food Processes https://doi.org/10.1016/B978-0-12-812465-9.00017-7
starchy materials such as corn or rice flour are often added to the slurry. The starch is then converted into fermentable sugars during the cooking process. The first filtration taking place in a tank eliminates residuals such as the hull of the grains. A clarified broth is the result of this operation. Hops leaves or hops extracts are now added to the broth and the mixture is heated in a cooker. Hops extracts come generally from a CO2 supercritical extraction process (see Chapter 7.7). B978-0-12-812465-9.00020-7 Hops gives beer its bitter taste. Cooking helps in the preservation of the broth. The broth is further separated, filtered, and cooled from 200°C to 40°C in a heat exchanger.
7.4.3 MANUFACTURING In order to increase their productivity, brewers are increasingly turning to the production of high-concentration beers that are ultimately diluted with high-purity process water. The broth is aerated with air but pure oxygen can be used in certain cases to boost the condition of the yeast that is added. As the
451
# 2019 Elsevier Inc. All rights reserved.
452
7.4. GASES IN BREWERIES
fermentation progresses, sugars are converted into alcohol and carbon dioxide. The fermentation process is carefully temperature-monitored: 12–20°C for high fermentation producing ale and 8–10°C for low fermentation producing lager. The secondary fermentation lasts from several days to several weeks. The young beer will mature in large tanks at low temperatures (0°C). The fermentation process continues somewhat and beer becomes paler and saturated in carbon dioxide. Beer is filtered on a silica-based material to separate it from the yeast and from the suspended solids. This step can also be accomplished after the dilution stage. In this case, process water must be deaerated to levels of about 50 ppb for residual oxygen (see Chapter 7.5.1). After dilution of the concentrated beer, carbonation of the finished product is required in order to obtain a CO2 concentration of 4– 8 g/L prior to transfer to the finishing tank.
7.4.4 PACKAGING Following a flash pasteurization at 70°C, beer is packaged in kegs, cans, or bottles. Following a purge with CO2 or N2, bottles are filled and capped. The finished product is then pasteurized. The filling operation is fully automatic. The introduction of the beer in the bottle is performed while maintaining the filling bowl under a pure CO2 or CO2/N2 mixture. This allows achieving a constant filling level in bottles and prevents the reentry of oxygen into the beer. The final dissolved O2 level in the bottled beer, which is key for the long preservation of beer, is usually around 150–250 ppb. The transfer of beer in the prior steps from one stage to the other is often done under gaseous pressure such as beer moving from tank to tank and filtration. This prevents the use of
pumps and the possible accidental reentry of oxygen into the beer. Breweries produce their own CO2 coming from the fermentation step. Due to seasonal production and some other satellite activities such as soft drink production, CO2 as a spot utility can be bought from industrial gas companies. However, due to the cost difference between CO2 and nitrogen in some areas, when possible the users can switch from CO2 to nitrogen for purges of empty pipes and tanks before beer filling to prevent air oxidation.
7.4.5 ROLE OF DISSOLVED GASES The role of the different dissolved gas concentrations in the beer depends of the type of beer. When the presence of CO2 is high, the foam formation will be high when serving in a consumer’s glass. English beers are generally low carbonated and are drafted with a CO2/N2 mixture pressure coming from appropriate gas cylinder mixtures (e.g., 80%N2/20%CO2 and other mixture ranges). During sport events intervals similar low CO2 content gas mixtures are also used in order to dispense quickly the consumers glasses without creating too much foam expansion in very short time. Guinness beer has a small metallic or plastic sphere inside the can filled with nitrogen under pressure that opens at the same time as the can. The role is to release fine bubbles at the surface, giving a similar creamy taste to draught beer.
7.4.6 CO2 RECUPERATION PLANTS IN BREWERIES Companies install their own CO2 recovery plants with purification processes in order to reuse the CO2 all along the beer process such as beer moves, inerting, soft drink carbonation,
7. FOOD PROCESSING: ALL THE FOOD INDUSTRY SECTORS
7.4.7 CONCLUSION AND PERSPECTIVES
and filling cylinders to be delivered to bars. As a general remark, the economical process for CO2 recovery from any process generating CO2 as a byproduct depends on the molecule quantity generation, the purity, and the seasonal flow consistency; this is not a good option in all situations. Asco: https://www.ascoco2.com/en/co2production-and-co2-recovery-plants/ GEA: https://www.gea.com/en/products/ gea-co2-recovery.jsp Techno Project Industriale: https://www. tecnoproject.com
453
7.4.7 CONCLUSION AND PERSPECTIVES The beer industry is a wide sector as almost all countries have such industries, even if some exceed others because beer is considered a national heritage there, such as Germany, the United Kingdom, Belgium, Australia, and the United States. Current trends also include specific beers and craft beers in microbreweries.
7. FOOD PROCESSING: ALL THE FOOD INDUSTRY SECTORS
7.4 Gases in Breweries Philippe Girardon Air Liquide, Paris, France
Among the different steps of this process, gases play the following role:
7.4.1 MALTING This step lasts for 8–9 days and can be done outside the beer manufacturing plant by different specialized companies linked to the grain business. After being cleaned, calibrated, and sorted, the barley grains are soaked in a tank containing pure deionized water. This leads to germination of the grains. Normal oxygenated water with air is sufficient. The oxygenation of this water with pure oxygen can accelerate the start of the germination process, which takes place at a temperature of about 25°C. However, references are not frequent. The germination is stopped by a flow of hot air (70–85°C). Its intensity influences both the flavor and the color of the beer. From this point on, barley is now referred to as malt. Sprouts are separated from the grains before storage in a silo.
7.4.2 BREWING The brewing process lasts for about 10 hours. Malt is ground first in a mill. The malt flour is mixed with water and becomes a slurry. Other
Gases in Agro-food Processes https://doi.org/10.1016/B978-0-12-812465-9.00017-7
starchy materials such as corn or rice flour are often added to the slurry. The starch is then converted into fermentable sugars during the cooking process. The first filtration taking place in a tank eliminates residuals such as the hull of the grains. A clarified broth is the result of this operation. Hops leaves or hops extracts are now added to the broth and the mixture is heated in a cooker. Hops extracts come generally from a CO2 supercritical extraction process (see Chapter 7.7). B978-0-12-812465-9.00020-7 Hops gives beer its bitter taste. Cooking helps in the preservation of the broth. The broth is further separated, filtered, and cooled from 200°C to 40°C in a heat exchanger.
7.4.3 MANUFACTURING In order to increase their productivity, brewers are increasingly turning to the production of high-concentration beers that are ultimately diluted with high-purity process water. The broth is aerated with air but pure oxygen can be used in certain cases to boost the condition of the yeast that is added. As the
451
# 2019 Elsevier Inc. All rights reserved.
452
7.4. GASES IN BREWERIES
fermentation progresses, sugars are converted into alcohol and carbon dioxide. The fermentation process is carefully temperature-monitored: 12–20°C for high fermentation producing ale and 8–10°C for low fermentation producing lager. The secondary fermentation lasts from several days to several weeks. The young beer will mature in large tanks at low temperatures (0°C). The fermentation process continues somewhat and beer becomes paler and saturated in carbon dioxide. Beer is filtered on a silica-based material to separate it from the yeast and from the suspended solids. This step can also be accomplished after the dilution stage. In this case, process water must be deaerated to levels of about 50 ppb for residual oxygen (see Chapter 7.5.1). After dilution of the concentrated beer, carbonation of the finished product is required in order to obtain a CO2 concentration of 4– 8 g/L prior to transfer to the finishing tank.
7.4.4 PACKAGING Following a flash pasteurization at 70°C, beer is packaged in kegs, cans, or bottles. Following a purge with CO2 or N2, bottles are filled and capped. The finished product is then pasteurized. The filling operation is fully automatic. The introduction of the beer in the bottle is performed while maintaining the filling bowl under a pure CO2 or CO2/N2 mixture. This allows achieving a constant filling level in bottles and prevents the reentry of oxygen into the beer. The final dissolved O2 level in the bottled beer, which is key for the long preservation of beer, is usually around 150–250 ppb. The transfer of beer in the prior steps from one stage to the other is often done under gaseous pressure such as beer moving from tank to tank and filtration. This prevents the use of
pumps and the possible accidental reentry of oxygen into the beer. Breweries produce their own CO2 coming from the fermentation step. Due to seasonal production and some other satellite activities such as soft drink production, CO2 as a spot utility can be bought from industrial gas companies. However, due to the cost difference between CO2 and nitrogen in some areas, when possible the users can switch from CO2 to nitrogen for purges of empty pipes and tanks before beer filling to prevent air oxidation.
7.4.5 ROLE OF DISSOLVED GASES The role of the different dissolved gas concentrations in the beer depends of the type of beer. When the presence of CO2 is high, the foam formation will be high when serving in a consumer’s glass. English beers are generally low carbonated and are drafted with a CO2/N2 mixture pressure coming from appropriate gas cylinder mixtures (e.g., 80%N2/20%CO2 and other mixture ranges). During sport events intervals similar low CO2 content gas mixtures are also used in order to dispense quickly the consumers glasses without creating too much foam expansion in very short time. Guinness beer has a small metallic or plastic sphere inside the can filled with nitrogen under pressure that opens at the same time as the can. The role is to release fine bubbles at the surface, giving a similar creamy taste to draught beer.
7.4.6 CO2 RECUPERATION PLANTS IN BREWERIES Companies install their own CO2 recovery plants with purification processes in order to reuse the CO2 all along the beer process such as beer moves, inerting, soft drink carbonation,
7. FOOD PROCESSING: ALL THE FOOD INDUSTRY SECTORS
7.4.7 CONCLUSION AND PERSPECTIVES
and filling cylinders to be delivered to bars. As a general remark, the economical process for CO2 recovery from any process generating CO2 as a byproduct depends on the molecule quantity generation, the purity, and the seasonal flow consistency; this is not a good option in all situations. Asco: https://www.ascoco2.com/en/co2production-and-co2-recovery-plants/ GEA: https://www.gea.com/en/products/ gea-co2-recovery.jsp Techno Project Industriale: https://www. tecnoproject.com
453
7.4.7 CONCLUSION AND PERSPECTIVES The beer industry is a wide sector as almost all countries have such industries, even if some exceed others because beer is considered a national heritage there, such as Germany, the United Kingdom, Belgium, Australia, and the United States. Current trends also include specific beers and craft beers in microbreweries.
7. FOOD PROCESSING: ALL THE FOOD INDUSTRY SECTORS