VIEW ARTICLE    DOI: 10.1094/ASBCJ-49-0098

Effects of Aging on Hops and Liquid CO₂ Hop Extracts. M. A. Priest, J. A. Boersma, and S. A. Bronczyk, Pfizer Inc., Brewery Products, Milwaukee, WI 53212. J. Am. Soc. Brew. Chem. 49:0098, 1991.

The effects of aging on hops and liquid CO₂ hop extracts were studied for 29 months. A single lot of Willamette ops was extracted at approximately six-month intervals during the aging process. Pilot beers were brewed using the hops and the corresponding extract at the same intervals. The effects of aging on the hops and extracts were monitored using high-performance liquid chromatographic and spectrophotometric analyses for α- and β-acids. The hop volatiles were monitored using gas chromatography. Analytical results showed that although the hops changed over time as indicated by α- and β-acids, hop volatiles, and hop storage index levels, the extracts remained essentially unchanged from the time of extraction. Aged hops and extracts from aged hops had similar hop-acid profiles. Analysis of the iso-α-acid of pilot beers brewed using the aged hops and extracts confirmed these trends. Results showed decreasing ratios of iso-α-acid to BU in beers brewed with older hops. In contrast, beers brewed with aged CO₂ extracts showed constant ratios of iso-α-acid to BU. Gas chromatographic analysis of the hops showed a loss of volatiles during aging, whereas analysis of the aged extracts showed no significant change.

Keywords: Hops, Hop extracts, Aging, α-acids, β-acids, Hop-volatiles