The total contents of phenolic acids measured by high-performance liquid-chromatography were 5-8 mg/litre in beers brewed in Ireland whereas 16-40 mg/litre were present in four other beers. In all beers the predominant phenolic acids were vanillic, p-coumaric and ferulic acids. Free phenolic acids were extracted from Emma barley grains and malt in very small amounts (15-28 mg/kg) but larger quantities (191 mg/kg) were released on mashing the malt. Little change occurred in the contents of phenolic acids on processing a lager wort through to the finished beer. Treatment with excess Polyclar AT removed astringent flavour and phenolic acids from an experimental ale but this flavour loss could not be accounted for by the adsorption of phenolic acids. The flavour threshold for a nine-component phenolic acid mixture in lager was between 50 mg/litre and 100 mg/litre.Key words: adsorbent, astringent taste, beer, highperformance liquid-chromatography. phenolic acids, wort. IntroductionInterest in the phenolic constituents of beers has concen trated closely on those polyphenols implicated in nonbiological haze formation.27 Sporadically, attention has turned to the still uncertain impact on flavour of the numerous simple and complex phenolic compounds present in beer. 71219-20-22'15 In common with most vegetable matter the raw materials of brewing contain a diversity of phenolic compounds, but only small amounts occur therein in a simple free state.29 Usually, phenolic substances are present in living tissues in conjugated forms, of which the most com mon type is the phenolic glycoside. Significantly, in this structural form the toxicity ofdiphenols(e.#. protocatcchuic acid) for living organisms is decreased greatly. Caffeic acid, the most common of the hydroxycinnamic acids, occurs most frequently as a quinic acid ester such as chlorogenic acid.29 Another hydroxycinnamic acid, ferulic acid, is usually bound to cell wall cellulose or associated with protein, and can inhibit germination if free in cereal grains.The quantitative analysis of plant extract for simple phenolic substances has improved greatly in recent years through the application of high-performance liquidchromatography (HPLC). Using this technique substituted hydroxybenzoic and hydroxycinnamic acids from many sources have been separated8-'-13-33-'8''"-49-51-56 but the glycosides and quinic acid esters of phenolics have been less exten sively studied.5-9-'6-30-52-39 Several reports '10-11-21-51'12-43'14 refer to the use of HPLC for measuring the contents of simple phe nolic acids in worts and beers. While there is general agree ment on the qualitative composition of beers the amounts of the different phenolic acids can vary widely. In a compre hensive study53-54 of phenolic acids in German beers the indi vidual acids were found usually at much less than 10 mg/litre and frequently amounted to less than I mg/litre. For some phenolic acids, especially the hydroxybenzoic acid deriva tives, the levels reported by other workers42-43 for some American beers were up...

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Four high-molecular weight proteose fractions from beer were precipitated to varying extents by four different tannin fractions, as shown turbidimetrically in a simple assay. According to this test the most acidic proteose fraction reacted least with all four tannins and the formation of insoluble proteose-tannin complexes was strongly dependent on pH. Moreover, tannins obtained from hops displayed greater tanning power with beer proteoses than did either a tannin isolated directly from barley or one prepared by aerial oxidation of barley prodelphinidin B3. The different reactivities of tannins to proteoses, however, did not correlate well with their reactivities to cinchonine sulphate (CS). Whereas the amounts of break precipitated on boiling a wort moderately were related to the amounts of hop tannins added, barley flavanols had little effect on break formation. In beer, about 50% of the proteoses were of low molecular weight (< 10,000 Daltons) and some were complexed with flavanols. In contrast, isolated fractions of high molecular weight beer proteoses (MW> 10,000 Daltons) were not associ ated with flavanols. The most acidic of these proteoses were the least stable in solution, being precipitated from beer by down-shifts in pH. The tanning power of unstabilised beer as measured by reaction with cinchonine sulphate was shown to arise from the cumulative effects of at least four different beer components, which should be considered when interpreting the effects of different haze-stabilisation treatments.