4. Biological and process engineering

4.1 Fermentation processes and yields

Must aeration has a strong impact on fermentation and aging reactions. During fermentation, aeration facilitates the synthesis of fatty acids and generally makes it possible to exceed 1 · 10 ⁸ cells/ml obtained under anaerobic conditions. In cases where a high alcoholic strength (13-15%) is desired, it is important to have a yeast population of around 1 · 10 ⁸ cells/ml. Aeration during pump-overs helps prevent premature fermentation stoppages due to a low yeast population. The quantity of oxygen to be added is in the order of 10 to 20 mg of oxygen/liter of must.

The addition of oxygen, when the wort is not sensitive to oxidation...