PHENOLIC CONSTITUENTS OF BEER AND BREWING MATERIALS .4. FURTHER OBSERVATIONS ON ANTHOCYANOGENS AND CATECHINS AS HAZE PRECURSORS IN BEER

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. 1969 The Institute of Brewing & Distilling