EUROPEAN BREWERY CONVENTION-HAZE AND FOAM GROUP PHENOLIC CONSTITUENTS OF BEER AND BREWING MATERIALS IV. FURTHER OBSERVATIONS ON ANTHOCYANOGENS AND CATECHINS AS HAZE PRECURSORS IN BEER

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Abstract
An earlier supposition that catechins (flavan-3-ols) can favourably influence the stability of a beer by co-polymerizing with flavan-3: 4-diols has been experimentally justified. D-(+)-Catechin, however, is also a direct haze precursor, particularly of chill haze, and its effect is most marked under conditions of high air content when it polymerizes relatively rapidly by an oxidative mechanism. The haze-inducing behaviour of a biflavan anthocyanogen isolated from barley is a little different from that described previously for a very similar anthocyanogen (component 12) from beer. A synthetic 5:7:3′:4′-tetrahydroxyflavan-3:4-diol appears to differ only slightly as a haze precursor from its stereo-isomer, beer component 73. These findings are considered in terms of probable chemical structures. Traces of an anthocyanogen, identical on paper chromatograms with a synthetic 5:7:3′:4′-tetrahydroxyflavan-3:4-diol, and thus stereo-isomeric with beer component 73, are present both in polyamide-beer adsorbates and in barley.

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