Preparation of adjustable yeast
Yeast reproduction in the propagation apparatus. Before proceeding with the reproduction of yeast, propagation devices must be thoroughly washed and washed, disinfected with chemical agents and sterilized with dry steam under pressure 0,5 at.
After 0,5 hours the beer drain cock in the propagation device is closed, followed by an inoculation tube in this way, that a glass stopper, taken out of 70% alcohol and fired with a flame, is slipped into the rubber tube stretched over it. Cotton wool filters are slid over the air tubes before they are closed, previously sterilized within 3-4 hours at 120 ° C.
The vent valve located at the stub ending with an air filter must be permanently open, to prevent the build-up of a vacuum in the tanks and their destruction.
The wort sterilizer is sterilized simultaneously with the fermentation tanks or during this time, when the wort is boiled in it. The steam generated during the wort boiling sterilizes the entire device.
Wort containing usually 12% by weight of the extract is indirectly heated with steam. After cooking for half an hour, all taps are gradually closed except for the vent valve, a cotton wool filter is attached, compressed filtered air is supplied and the cooling of the wort begins by supplying cold water to the sterilizer jacket. During cooling, the wort is aerated.
The wort cooled to 15 ° C is forced into the propagator, closing the air supply. Then it is inoculated with yeast culture - yeast multiplied to quantity 1-5 dm3. The yeast culture is introduced through an alcohol-fired port.
After fermentation, the propagator is filled with the wort and its contents re-aerated. The yeast multiplication process is carried out at a temperature of 10 ° C during 10-14 days.
The yeast grown in this way is sent for further multiplication in the multiplier, mixing them with the wort in ratio 1 : 3 or with the addition of even more wort.
Part of the yeast is left in the propagator and, by mixing with a new batch of sterile wort, the cycle is repeated under fed-batch fermentation conditions..