Yeast: Difference between revisions

While it is clear that the introduction of oxygen into wort can have a negative impact on quality, it is intentionally added during wort cooling. Yeast requires oxygen to synthesize UFAs and sterols, which are critical cell membrane components that impact membrane fluidity. Depraetere et al. showed that under normal conditions, oxygenation of cold wort (8 ppm O 2 ) had no significant impact on the level of aging staling indicators for ale or lager beers over a 12 month ambient shelf-life test (14). At this stage of the process, oxidation of wort compounds appears to play little to no part compared with the change of aroma and flavor from yeast metabolism. It is important to note that the wort oxygenation rate can impact the levels of sulfites produced by lager yeast; increased oxygenation can cause a reduction in sulfite levels, leading to a loss of scavenging activity for carbonyl compounds, such as E2N (22).<ref name=golston>Golston AM. [https://www.mbaa.com/publications/tq/tqPastIssues/2021/Pages/TQ-58-1-0322-01.aspx The impact of barley lipids on the brewing process and final beer quality: A mini-review.] ''Tech Q Master Brew Assoc Am.'' 2021;58(1):43–51.</ref>

*Depraetere, S., et al. 2008. The influence of wort aeration and yeast preoxygenation on beer staling processes. Food Chem. 107(1):242-249.

==Preparing yeast for fermentation==