Phenolic Acids in Beers and Worts

Abstract

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...

Micro-Malting for the Quality Evaluation of Rye (Secale cereale) Genotypes

“…As reported by others, rye soluble protein levels were observed to be considerably higher than those of barley (15,26,27,28). Soluble protein was significantly impacted (p < 0.05) by all variables evaluated, but the differences were often relatively small ( Table 2).…”

“…The phenolic acid content of wort was determined according to a modification of method reported by McMurrough et al [26]. After adjusting pH to 2.0-2.5, 5 mL of the wort was extracted three times with ethyl ether/ethyl acetate (5/5, v/v).…”

Determination of polyphenols in beer by an effective method based on solid-phase extraction and high performance liquid chromatography with diode-array detection

“…The levels of polyphenols found are in agreement with the data already published. McMurrough et al (1984) determined the total content of phenolic acids in beers. The concentration range found was from 5 to 8 mg/l.…”

Partial Purification of Ferulic Acid Esterase from Malted Barley

“…The fluorescence is due to the ferulic acid (4-hydroxy-3-methoxy cinnamic acid), which is attached to the C-5 position of some arabinose residues 1,25 . Evidence for the action of ferulic acid esterase activity in the germination stage of malting is lacking, but ferulic acid release has been detected during kilning 21 and mashing 22,27 when the optimum temperatures were 44-45°C 23,27 . Ferulic acid occurs in beer 22 , it may give rise, via decarboxyation, to 4-vinyl guaiacol, a strongly flavoured substance 9,13,20,26,28,30 .…”

“…Evidence for the action of ferulic acid esterase activity in the germination stage of malting is lacking, but ferulic acid release has been detected during kilning 21 and mashing 22,27 when the optimum temperatures were 44-45°C 23,27 . Ferulic acid occurs in beer 22 , it may give rise, via decarboxyation, to 4-vinyl guaiacol, a strongly flavoured substance 9,13,20,26,28,30 . When isolated barley aleurone layers were incubated with gibberelic acid some cell wall degradation occurred, but the ferulic acid was still attached to arabinoxylan oligomers 15,16 , and so in this case ferulic acid esterase was not active.…”