Changes

In general, the best practice is to limit oxygen at packaging time, although brewers have had success packaging beers with living ''Brettanomyces'' without purging the bottles with CO². Other compounds can serve as anti-oxidants in beer. For example, sulfates are converted into sulfites by yeast, and sulfites postpone the formation of free radicals. Lower-weight polyphenols, which originate from malt (70-80%) and hops (20-30%), are thought to be free radical scavengers and anti-oxidants, however other polyphenols have been identified as pro-oxidants and the effectiveness of antioxidant activity in general for polyphenols is debatable in the scientific literature (although their impact in the mash and boil has been established as positive). Maillard reactions from malting/roasting and wort boiling also create anti-oxidants, and in general the darker the roasting the more anti-oxidant the malts will be <ref name="Vanderhaegen_2006" />. Lactic acid and lactic acid fermentation are thought to also help serve as anti-oxidants, although this has not be studied in sour beer <ref>[https://www.ncbi.nlm.nih.gov/pubmed/10904049 Free radical scavenging and antioxidant effects of lactate ion: an in vitro study. Groussard C, Morel I, Chevanne M, Monnier M, Cillard J, Delamarche A. 1985.]</ref><ref>[https://www.sciencedirect.com/science/article/pii/S0740002011000530 Effect of lactic acid fermentation on antioxidant, texture, color and sensory properties of red and green smoothies. Raffaella Di Cagno, Giovanna Minervini, Carlo G. Rizzello, Maria De Angelis, Marco Gobbetti. 2011.]</ref>.

===General Effects of Temperature===