Control of beer fermentation process

During the main fermentation period, the focus of technical control is temperature, concentration and time, which restrict each other and complement each other. When the fermentation temperature is low, the concentration decreases slowly and the fermentation time is long; on the contrary, when the fermentation temperature is high, the concentration decreases rapidly and the fermentation time is short. The basis for the control of the three is related to the type of product, yeast species, and wort composition. The purpose of the control is to achieve the required degree of fermentation and metabolites in the shortest time.

• Temperature control

Beer fermentation is a variable temperature fermentation, and the fermentation temperature refers to the highest temperature in the main fermentation stage. For traditional reasons, the fermentation temperature of beer is generally lower than the optimum growth temperature of brewer's yeast (25-28°C). The inoculation temperature of the upper fermented beer is generally controlled at 18-20°C, and the inoculation temperature of the lower fermented beer is generally controlled at 8-10°C.

The main fermentation starting temperature of the low-temperature fermentation process is 5-7°C, generally 6.5-7°C. The maximum fermentation temperature varies with different strains of bacteria and different wort components, and is generally between 8 and 10 °C. The temperature is low, which is beneficial to reduce the production of fermentation by-products, the formation of α-acetolactic acid is reduced, the production of diacetyl, higher alcohols, acetaldehyde, H2S and dimethyl sulfide is also reduced, and the beer tastes fresh and foam performance. Well, good for light beers.

The temperature at the end of fermentation is generally controlled at 5°C. Lower the temperature to make the yeast agglomerate and precipitate. Only a certain concentration of yeast is retained in the wine liquid, which is convenient for post-fermentation and diacetyl reduction; continue to lower the temperature to 0~-0.5 °C, which is convenient for low-temperature storage, so as to facilitate the clarification of the wine and the saturation of carbon dioxide, otherwise it will be Extend the storage period.

• Concentration control

Under certain conditions of yeast species and wort components, the concentration control is controlled by adjusting the fermentation temperature and fermentation time. If the fermentation is vigorous and the sugar consumption is fast, it is necessary to appropriately reduce the maximum fermentation temperature and shorten the holding time of the maximum temperature; on the contrary, it is necessary to prolong the holding time of the maximum temperature or adopt a slow cooling method to promote sugar consumption.

• Time control

Under certain requirements of wort composition, yeast activity and certain degree of fermentation, the fermentation time mainly depends on the fermentation temperature. The higher the fermentation temperature, the shorter the fermentation time, and vice versa.

The main fermentation time of the following fermentation is generally controlled within 7 to 10 days. Low-temperature and slow-fermented wine, soft and mellow flavor, fine and lasting foam, but low equipment utilization. The main fermentation time of the above fermentation is generally controlled within 5 to 8 days, the fermentation speed of the yeast is fast, the fermentation time is short, the aroma is prominent, and the utilization rate of the equipment is high.

The main fermentation at low temperature for a long time can make the fermentation liquid ferment in a balanced manner, the pH will drop slowly, and the hop resin and protein will be precipitated in a small amount to make the beer mellow, with good aroma and fine and long-lasting foam. The main fermentation time of 10-12ºP beer is generally 6-8 days.