Kvasny Prumysl, 2008 (vol. 54), issue 2

Colour changes during beer aging.Peer-reviewed article

Jan ŠAVEL, Petr KOŠIN, Adam BROŽ

Kvasny Prum. 2008; 54(2): 30-37 | DOI: 10.18832/kp2008003  

Spectrum changes of yellow, orange and yellow-red oxidation products of epicatechin with their typical absorption maximum around 430 nm were studied. Oxygen is necessary for the non-enzymatic formation of these substances and their formation increases with growing pH value and Fe2+ and Cu2+ concentration. Based on the a.m. reasons, colour products are formed more easily in tap water than in deionized one. The colour substances formed can partially discolour with falling pH value and increasing concentration of reducing substances. Colour substances once formed cannot be fully reversibly reduced, which corresponds to the model of a partially reversible...