Traditional fermentation techniques have a few downsides. Time being the most obvious one, and with time comes the additional requirements for storage space. There are also some process specific pitfalls which mainly revolve around yeast health. Carrying too much yeast into secondary, abrupt temperature changes as well as unhealthy yeast (low viability) can all result in autolysis.
Once autolysis happens the contents are irrevocably destroyed. It happens far quicker than many suspect. Controlling pH during fermentation is important since it is a good indicator of things going wrong. A rise in pH is bad news. If this happens then the usual causes are mainly infection or autolysis.
Other pitfalls can include incomplete decomposition of by-products during a poorly conducted secondary phase.
Annemüller suggests an accelerated fermentation schedule, starting cold, then conditioning warm. In essence the equipment needed is not different from the equipment for classic fermentation and thus suitable for home brewers without requiring further investments.
Here is how to do it
1. Primary Fermentation (Hauptgärung)
Until the yeast growth phase is complete the fermentation proceeds just like with the classic schedule.
- Pitch temp 6°C
- Ferm temp 8°C
- Duration 2-3 days
However, once the growth phase is over (high Kräusen), the temperature is then allowed to rise to 9..10°C for a further 2-3 days until between 1..2.5% residual extract is left to ferment. Note that this twice as high as during classic cold or warm schedules. A possible explanation would be that the increased amount of yeast further shortens the conditioning time.
- Ferm temp 10°C
- Duration 2-3 days
- Transfer (Schlauchen) ΔEs 1..2,5%
2. Secondary Fermentation (Reifung)
Transfer has to happen into a vessel capable of withstanding 2-3 BAR pressure since the resulting settings on the pressure relief valve will be much higher. Since home brewers ferment often in soda or beer kegs this should not pose a problem for many. If your outfit is a microbrewery, then I’m afraid an investment in a pressure tank may be needed at this stage.
- Ferm temp 10..15°C
- Duration 3..7 days
The pressure relief valve is set to the desired carbonation level and the maturation happens over the next seven days at 10..15°C. Some brewers opt to step the pressure settings in order to reduce the formation of by products even further.
3. Cold Conditioning
After the secondary fermentation is complete the beer is transferred (Umdrücken) to yet another vessel whose temperature is at 0..3°C. Since maturation is complete a yeast shock from the sudden temperature drop is not expected.
- Temperature 0..3°C
- Duration 7 days
Now the beer undergoes it’s cold conditioning phase where it spends a further 7 days before it is filtered or fined.
- [GAHM] Gerolf Annemüller, Hans-J. Manger. Gärung und Reifung des Bieres (2. Überarbeitete Auflage).