During fermentation, pure carbon dioxide is given off for a considerable period of time, and our sixth raw material enters the picture.
Approximately 24 hours after the brew enters the fermenting tank, the yeast will begin to actively utilise the wort nutrients. They emerge from the early stationary period, called the lag phase, into the period of accelerating multiplication, which will rapidly approach maximum multiplication in a period of logarithmic growth. The carbon dioxide gas produced is led off to a compressor located in the brewery's engine room from where it is stored and later returned to the beer. Before the gas is collected, it is tested for air content and must be at least 99.9% carbon dioxide. The presence of oxygen in the collected gas will present many difficulties further in the process. After the carbon dioxide is compressed, it is passed through a condenser which liquefies the gas. It is then stored in liquid form in a large tank. Liquid carbon dioxide in later withdrawn from this tank and passed through an evaporator which converts the liquid back to its gaseous form.
After completion of either lager or ale fermentation, the attemperator glycol is turned on full, and the brew is cooled down to a temperature which approximates storage temperature.
Now the fermentation picture is complete. The wort solution containing sugars, proteins and other products has been converted to an alcoholic solution called beer. When the beer has been reduced to the temperature desired in the fermenter, the brew is racked to the primary storage cellar where the aging process commences. Here again we encounter a distinct difference between lager and ale. Lager brews are aged at lower temperatures, usually 0-2°C (32-36°F), while ale is stored at 4-10°C (40-50°F).
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