The role of post-fermentation and storage period of beer

The fermented liquor after the main fermentation of wort is called green beer, also known as new beer. At this time, the carbon dioxide content of the beer is insufficient, and the volatile flavor substances such as diacetyl, acetaldehyde, and hydrogen sulfide have not been reduced to a reasonable level. , the beer is not clear enough, generally need several weeks or months of post-fermentation and beer storage period. The maturation and clarification of the beer are completed during the post-fermentation and storage period.

During the post-fermentation process, some biochemical, chemical and physical changes are still going on slowly, and their main roles are as follows:

Carbon dioxide saturation

After the tender beer is drunk, the initial post-fermentation temperature is still maintained at 3~5°C, so that the residual fermentable sugars (mainly maltose and maltotriose) continue to ferment, and the carbon dioxide produced is continuously dissolved in the closed beer storage container. In the beer, it is saturated. At the same time, at a relatively high post-fermentation temperature, diacetyl can still be reduced quickly.

After carbon dioxide saturation, the longer the beer storage time, the more stable the beer's adsorption of carbon dioxide, and the better the beer quality. Carbon dioxide in saturated beer is generally considered to be in three states: gaseous carbon dioxide dissolved in the beer at different temperatures and pressures; carbon dioxide absorbed by colloidal substances in beer; carbon dioxide combined with beer components

Brewery equipment fermenter and bright beer tanks

The maturity of beer 

In the post-fermentation period, the role of promoting the maturation of beer is mainly to use carbon dioxide emission to eliminate the green-flavored substances contained in tender beer, such as diacetyl, hydrogen sulfide and acetaldehyde, which are simultaneously discharged in large quantities, reducing the immature taste of beer. Accelerates beer maturation. The diacetyl content of mature beer should be below 0.1mg/kg; a very small amount of hydrogen sulfide is an essential component of beer flavor, excessive amount is harmful, and can give beer an unpleasant green flavor, which must be excluded; acetaldehyde content is strong in fermentation In the early stage of beer storage, with the emission of carbon dioxide, the acetaldehyde content began to decrease sharply, and the content remained low until the beer storage was completed.

Fermentation tanks/Unitanks customized

Clarification of beer 

The clarification of beer is the sedimentation of the suspended solids contained in the beer during the storage of the beer. The suspended solids in beer are mainly yeast cells, cold coagulation proteins, hop resins, protein polyphenol complexes, etc. After the post-fermentation is maintained for 7-10 days, the beer temperature is gradually lowered to 0-1 ℃, and the beer storage maturity period is entered. During the long beer storage period, the suspended matter in the beer slowly settles down at low temperature and low pH value, so that the beer liquid is gradually clarified, and the taste of the beer becomes more mature. At a lower beer storage temperature, some protein-polyphenol complexes that are easy to form turbidity are gradually precipitated and precipitated first or removed by filtration, which improves the abiotic stability of the beer, thereby increasing the shelf life of the finished beer.

During the post-fermentation period, the beer should be absolutely prevented from contacting the air to maintain the reduced state of the beer, otherwise not only the flavor, foam, color and abiotic stability of the beer will be seriously affected by oxidation, but also susceptible to miscellaneous bacteria and even spoilage.