Detailed steps of beer fermentation Traditional beer fermentation methods

1. Pre-fermentation: After the wort inoculated with yeast (7-8℃) enters the pre-fermentation, it is suspended in the growth zone for several hours. When the cell concentration reaches 2× 107 cells /ML, the yeast begins to grow and reproduce. Bubbles begin to appear on the surface of wort, which is called pre-fermentation. Pre-fermentation time varies with inoculation temperature and inoculation amount. Low temperature fermentation is about 16-20h, and medium temperature fermentation is about 12- 14h. In the pre-fermentation stage, the sugar level of yeast is slow. Due to the metabolism of yeast, the temperature of fermentation broth will naturally increase by 0.6-65438 0.0℃. After the pre-fermentation, the fermentation liquid will be pumped into the main fermentation chamber.

2. Main fermentation: The main fermentation is carried out in a well-insulated, clean and hygienic fermentation chamber, and a ventilation system is installed indoors. The main fermentation is mostly open square or round, with wooden, steel, aluminum and concrete fermentation containers, and the fermentation temperature in the main fermentation stage is 5-6 degrees. The early stage of main fermentation is the stage of yeast reproduction. Yeast uses fermentable sugar through respiration. When the fermentation reaches a certain level, the fermentation speed gradually slows down, which shows that the ethanol content increases rapidly. However, the speed of lowering blood sugar slows down, the change of PH value decreases, and the output of carbon dioxide decreases. At this time, yeast began to coagulate and precipitate, and the cell density of suspended yeast gradually decreased.

3. Post-fermentation: Post-fermentation, also known as wine storage, aims to complete the final fermentation of residual sugar, increase the stability of beer, fully charge CO2, fully precipitate protein and clarify the liquor; Remove the flavor of diacetyl, aldehydes, H2S and other tender wines to promote ripening; Try to make the liquor in a reducing state and reduce the oxygen content. After the main fermentation, liquor is not mature enough, and some extracts need to continue fermentation. Especially in the production of light beer, the content of fermentable sugar should be reduced as much as possible. In the main fermentation stage, the content of carbon dioxide in liquor is insufficient, so it needs post-fermentation to make the carbon dioxide contained in beer reach saturation level, and the volatile substances such as diacetyl and hydrogen sulfide produced by main fermentation are also reduced to the specified range through post-fermentation and wine storage.