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of beer is a complex process where yeast cells metabolize fermentable sugars, rendering alcohol and carbon dioxide.
When yeast is added ("pitched") into the wort, there is a lag in time before active fermentation can be observed. Yeast wants to grow and multiply, just like other cells, and it will use oxygen as long as it is available. While oxygen is used in aerobic respiration, the yeast grow, move and multiply using glucose (a sugar) and oxygen, creating carbon dioxide and water as waste products. Not until all the oxygen is used up will the yeast begin anaerobic respiration, meaning "growing and reproducing without oxygen". During this process yeast use glucose but no oxygen is available, and products of these reactions are ethanol and carbon dioxide. In both processes there are other by-products which influence flavor, some desirable and some not. Selection of yeast strain, temperature, oxygen content, proteins and wild bacteria can have extreme effects of flavor.
TIPS:
- Keep fermenters and ANYTHING that touches cooled wort sanitzed (but not sterilized) to prevent contamination.
- Select a fresh, healthy and appropriate yeast for the style of beer you are brewing.
- Keep temperature constant throughout the fermentation process. A change of as little as 5 degF can affect the taste of your beer.
- Oxygenate the wort before you pitch the yeast for optimal growth and health of the yeast.
- Use a "blow-off" tube on the primary fermenter to vent aggresive fermentation. Airlocks can become clogged and the pressure in the container can blow the lid off and make a huge mess.
- Ferment ales in a primary container for 5-7 days, then rack to a secondary for another 5-7 days.
- Ferment lager beers at cooler temps (around 50 degF) for up to 2 weeks in a primary. Rack into a secondary and let it rest at room temperature (diacetyl rest) for up to 24 hrs. Move secondary to cold temp (as low as 33 degF) for 1-3 months.