Polyphenols and Pyrazines in Beer during Aging¹

1 Cooperative investigation between the Science and Education Administration, U.S. Department of Agriculture, and College of Agricultural and Life Sciences, University of Wisconsin-Madison.

Presented at the 45th Annual Meeting, Portland, OR, April 1979.

Abstract

Concentrations of 18 polyphenols and 13 pyrazines in aging bottled beer were determined by high performance liquid chromatography with a reverse phase octadecyl-silica (μ-Bondapak®C₁₈) column. Ten to 50 μl of beer could be directly applied to the column and assayed. Most polyphenols decreased during storage for up to 84 days, but vanillic acid and epicatechin remained constant, and catechin and chlorogenic acid increased markedly. Quercetin was the polyphenol in largest quantity, followed by catechin. Pyrazines were monitored for 56 days' storage. Most levels decreased quickly during the first 48 hr. During the latter half of storage, increases were found in 2-methylpyrazine, 2,6-dimethylpyrazine, and 2-ethyl-5-methylpyrazine, but the remaining pyrazines did not change markedly after five days' storage. No significant changes were observed during storage of frozen beer or of lyophilized beer. No measurable loss in pyrazines occurred during lyophilization. The simple assay procedure has ready application for monitoring these compounds in beer stored under commercial conditions.

• Flavor-active compounds
• HPLC
• Storage changes