The Isolation and Identification of New Staling Related Compounds from Beer¹

1 Presented at the 43rd Annual Meeting, St. Louis, May 1977.

Abstract

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.

• Ethyl iso-valerate
• Ethyl 2-methyl butyrate
• Gas chromatography
• Staling
• Cacuum distillation