Acetone: water (3 : 1) extracts of milled barley grains contained simple monomeric, dimeric and trimeric flavanols in addition to higher molecular weight flavanoid tannins.Whereas ( + )-catechin and the simple individual oligomeric proanthocyanidins were readily separated by h.p.1.c. and t.1.c. fine resolution of the tanning components was not accomplished. Adsorption chromatography on Sephadex LH-20 permitted group separation and measurement of tanning components which were characterised as polymers of (+)-catechin and (+)-gallocatechin. Using h.p.1.c. little change in the contents of simple flavanols was detected during the malting of barley, neither were there substantial differences in flavanol contents between five different varieties of barley. The tannins appeared to be formed in the grain prior to harvesting, possibly by oxidation of simple flavanols, and were not artefacts of post-extraction treatments.

The highest concentrations of complexed and polymeric flavanols were found in the early runnings from a small-scale mash tun. Formation of break during and after boiling was accompanied by the removal of flavanols from solution, especially the complexed and polymeric fractions. Variations in boiling procedure affected the amount of break formed, the amount of residual soluble flavanols and the colloidal stability of the resultant worts. Colloidal stability in beer was influenced by the contents of simple flavanols and the availability of air during storage. Dimeric and trimeric flavanols seemed especially susceptible to oxidation which implied an important role in haze formation. Flavanols found in commercial beers were mainly monomeric and complexed forms.

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