About Matured Fermentation Broth

In most beer companies, the maturity of the fermentation broth is based on the reduction of the diacetyl index to the specified range and the expiry of the ageing period (from the sealing of the fermentation tank to the date of maturation of the beer). However, due to improper control of the process conditions or abnormal fermentation, some abnormalities or quality problems may arise in the matured fermentation broth, such as insufficient CO2 content, poor clarification of the fermentation broth, indicators that do not meet the requirements, colour or acidity that exceed the required indicators, poor taste quality and contamination with miscellaneous bacteria. When these quality problems are encountered, how are they generally adjusted and remedied?
1. In the post-fermentation wine age before the end of 3-5 days (wine age can be in the first 4-5 days, wine age is short in the first 3 days), the post-fermentation liquid to check. The checks may include:
① alcohol content and raw wort concentration;
② Diacetyl content and CO2 content;
③ turbidity of the fermentation broth;
④ other major physicochemical indicators such as total acid, pH, colour, etc;
⑤ Flavour quality.
In addition, microbiological indicators should be checked and analysed.
2. According to the results of inspection and analysis, the corresponding remedial measures to be taken are as follows:
① Adopt the method of co-filtration to solve the deficiencies in indicators such as alcohol content and raw wort concentration, colour and CO2 content. Before co-filtration, balance indicators need to be taken into account and, after co-filtration is completed, accurate measurements of the clear liquor are also carried out to ensure the quality of the finished beer.
② Poor clarification of the fermentation broth can be solved by appropriately extending the storage period, or by lowering and stabilising the storage temperature, or by using centrifuges etc.
③The problems that exist with poor taste quality are more difficult to deal with, but can be remedied appropriately. For example, some taste indicators can be adjusted by combining and filtering the mix, such as a slightly bitter and non-bitter, sour and non-sour, light and mellow tasting beer mix; occasionally, some high-foaming wine is added to deal with diacetyl taste or a heavier raw wine taste, and some companies use measures such as increasing the CO2 content and increasing the kill taste to improve the problem of poor taste. However, taste quality is an extremely important quality standard issue for beer and should be controlled primarily during the production process, preferably without the use of processing after the fermentation broth has matured.
④ Contamination with miscellaneous bacteria is a big no-no in beer production. As soon as an inspection reveals that a hair has been contaminated with miscellaneous bacteria, the tank should be marked and disposed of immediately. The key to identifying the problem is to disinfect and sterilise the whole system in good time afterwards.