Fermentation is carried out using conical tanks, which are not under pressure at the beginning. To discharge undesirable taste of volatile substances. Micro-pressure (down to 0.01-0.02 MPA) is used in the recovery of CO2. In the later stages of fermentation, when the external fermentation level reaches 70%, the tank is closed. Gradually increase the pressure to 0.08 MPA to saturate the beer with CO2. Increasing the pressure too early can lead to rapid yeast settling, which is detrimental to diacetyl reduction.
Pressurized fermentation is always accompanied by high-temperature fermentation. Although high temperature fermentation (above 13°C) can speed up fermentation. However, yeast proliferate strongly and produce excessive metabolic by-products. This will affect the quality of the beer. High-temperature fermentation can be avoided by pressurization measures. When pressurizing fermentation, it is important to control the time of pressurization. If it is too early, yeast proliferation will be inhibited and the fermentation rate will be affected. If it is too late, it will also increase the production of by-products. Therefore, it is advisable to pressurize gradually, section by section. Yeast inoculation is not pressurized, and the temperature is controlled at 10-12°C. When the degree of fermentation reaches 25%-30%, gradually increase the pressure to about 0.03 MPA. Then the fermentation temperature is increased to 16°C and the pressure is also increased to 0.16 MPA.