Flavonols detected as beer constituents are kaempferol and quercetin and myricetin. The glycosides present are astragalin, isoquercitrin, and rutin, together with trace amounts of several glycosides, which are doubtless derived from kaempferol and quercetin and contain two or more sugar residues. Phenolic and hydrocycinnamic acids present in the free state in beer are p-hydroxybenzoic, vanillic, and syringic, caffeic, p-coumaric and ferulic and sinapic acids. Esters and glycosides of phenolic and hydroxycinnamic acids present in beer comprise chlorogenic acid together with small quantities of neochlorogenic acid and a number of unidentified compounds which yield p-hydroxybenzoic, protocatechuic, vanillic, syringic, caffeic, ferulic, sinapic, and gentisic acids upon hydrolysis.
Keywords: beer brewing haze phenolic compound polyphenol raw materials