VIEW ARTICLE    DOI: 10.1094/ASBCJ-36-0027

The Isolation and Identification of New Staling Related Compounds from Beer. R. S. Williams and H. Wagner, Beverage Science Department, Labatt Breweries of Canada Ltd., London, Ontario N6A 4M3. J. Am. Soc. Brew. Chem. 36:0027, 1978.

Staled beers assume brandy-like, "winey" aroma and flavor characteristics in bottled products after about 3 mo in warm storage and intensify with time. The object of this study was to isolate from staled beer, under as mild conditions as possible, a fraction containing these winey characteristics and identify the responsible component(s). Preliminary fractionation is achieved by controlled, low temperature, vacuum distillation of beers, and extraction of a cut, trapped out in dry ice-acetone, into trichlorofluoromethane (Freon 11) yielding a concentrated extract. Preparative gas chromatography of this extract enables further refinement of the winey fraction by trapping the appropriate peak in a glass capillary U-tube immersed in crushed dry ice. These sealed U-tubes are crushed in the injection port of an analytical gas chromatograph and the winey fraction components investigated using mass spectrometry. Ethyl iso-valerate and ethyl 2-methyl butyrate are identified as important components in the staling of beers.

Keywords: Ethyl iso-valerate, Ethyl 2-methyl butyrate, Gas chromatography, Staling, Cacuum distillation.