Beer changes during secondary fermentation
During secondary fermentation, several physical, chemical, and biological reactions continue slowly to enhance the final flavor of beer. For instance,
After primary fermentation, the beer should be kept at a temperature of 3-5℃ to allow further fermentation of residual fermentable sugars like maltose and maltotriose. This additional fermentation results in the production of CO2, which is then dissolved into the beer in a sealed tank until it reaches a state of saturation. Furthermore, a higher temperature during secondary fermentation facilitates rapid reduction of diacetyl.
The CO2 produced at the beginning of secondary fermentation is released, carrying away any undesirable flavors and volatile substances. This process helps in the maturation of beer.
After 7-10 days, the beer is gradually cooled to 0-1℃. With the decrease in temperature and pH, yeast, cold sludge, and hop resin precipitate, resulting in clear beer with improved mouthfeel.
The lower temperature also causes proteins that can cloud the beer to separate and precipitate. These proteins are removed during filtering, which improves the non-biological stability of beer and extends its expiration date.
During secondary fermentation, it is crucial to protect the beer from exposure to air. Otherwise, oxidation can deeply affect the flavor, foam, color, and non-biological stability of the beer, making it prone to contamination.
Should a cold room be used for beer fermentation or maturation?
Our standard configuration includes a glycol water tank that is 2-3 times larger than the brewhouse. Some customers have mentioned that their local city water temperature is lower (around 23 degrees). They can use an ample amount of city water to initially cool the wort and then utilize a cold room or a small cooling system for wort cooling, fermentation, or maturation. Is this suitable?
Our suggestion is to maintain the standard configuration. As you know, the wort needs to be cooled from over 100 degrees Celsius to about 10 degrees Celsius within 40 minutes to produce high-quality beer. During fermentation, different beer styles require different temperature profiles at various stages. However, with a cold room, the temperature remains constant. Consequently, all the fermenters are cooled at the same temperature.
If we have a glycol unit, the temperature can be set according to your requirements. (The control unit has a temperature gauge, and each fermenter/bright tank is equipped with a solenoid valve and a temperature sensor). When the actual temperature exceeds the set temperature, the solenoid valve opens, initiating cooling until the desired temperature is reached. This provides greater flexibility compared to cold room cooling. Additionally, using a glycol unit for cooling the bright tank during maturation is also more effective.
Some brewmasters prefer having a cold room for the brewhouse. They place the bright tank in the cold room and primarily use it as a serving tank or for post-filling beer cooling. The temperature can remain consistent in this setup. If you also have this preference, it is acceptable to have a cold room.