VIEW ARTICLE DOI: 10.1094/ASBCJ-52-0127
Analysis of Free Fatty Acids, Fusel Alcohols, and Esters in Beer: An Alternative to CS2 Extraction. P. Alvarez and P. Malcorps, Unité de Brasserie et des Industries Alimentaires, Université Catholique de Louvain, Place Croix du Sud 2/Bte 7, B-1348 Louvain-la-Neuve, Belgium; A. Sa Almeida and A. Ferreira, Unicer-Uniào Cervejeira, S.A., Direcçào Qualidade Industrial, Leça do Balio, Portugal; and A. M. Meyer and J. P. Dufour, Unité de Brasserie et des Industries Alimentaires, Université Catholique de Louvain, Place Croix du Sud 2/Bte 7, B-1348 Louvain-la-Neuve, Belgium. J. Am. Soc. Brew. Chem. 52:0127, 1994.
Beer flavor compounds of routine interest were analyzed by gas chromatography using either direct headspace injection or solvent extraction. The headspace chromatographic method described here makes it possible to analyze dimethyl sulfide, ethyl acetate, propanol, isobutanol, isoamyl acetate, isoamyl and amyl alcohols, and less volatile compounds such as ethyl caproate (168° C) and ethyl caprylate (208° C) in less than 20 min. Two calibration methods are described: daily calibration or the use of an internal reference beer system, which considerably simplifies the calibration procedure for long-term use. Although rapid and accurate, headspace analysis discriminates against the less volatile compounds. A complementary chromatographic method, both quick and simple, was designed to assay amounts of caproic, caprylic, and capric acids; β-phenylethanol; and β-phenylethylacetate in fermenting wort and beer. In combination with headspace analysis, this method using hexanol as the extracting solvent yielded beer aroma profiles similar to those obtained with the carcinogenic solvent CS2. Repeatability of the two solvent extraction procedures was studied by replicating the analyses. The combined techniques were used to investigate relationships between flavor compounds and their formation in 48 lager beers.
Keywords: Beer flavors, Carbon disulfide extraction, Esters, Ester formation, Free fatty acids, Headspace analysis, Higher alcohols