Beer colour is the result of the concentration of highly coloured melanoidin and caramel compounds in solution. These compounds are primarily formed via Maillard type reactions between aldose type sugars and amino acid groups, which occur primarily during extreme heating stages of the malting and wort production phases of the brewing process i.e. malt kilning and wort boiling. Melanoidin compounds are extracted from the malt during mashing and form during boiling. Therefore, the desired colour of a beer may be achieved by employing malts of particular colour and boil times of appropriate duration.
However, as packaged beer may contain amino acids and reducing sugars in solution Maillard reactions may still occur in the product, particularly if the beer is subjected to storage under conditions that favour this reaction, namely elevated temperatures, long time periods or a combination of both. Studies have attributed colour increases during ageing to such Maillard reactions.
The polyphenols in beer are also subject to degradation via oxidation reactions catalysed by light, oxygen, oxidising agents, and heavy metals, to form darker coloured quinonoid bases that result in an increase in beer colour.Tags:beer, beer color beer colour