Comparison of the Contributions of Hop Pellets, Supercritical Fluid Hop Extracts, and Extracted Hop Material to the Hop Aroma and Terpenoid Content of Kettle-Hopped Lager Beers

Daniel C. Sharp (1), YanPing Qian (2), Jeff Clawson (1), and Thomas H. Shellhammer (1). 1. Oregon State University Department of Food Science and Technology, 100 Wiegand Hall, Corvallis, OR, U.S.A. 2. Oregon State University, Crop and Soil Sciences, 455 Crop and Soil Sciences, Corvallis, OR, U.S.A.
Brewers who create hop-forward styles such as American-style India Pale Ales typically add hops toward the end of or after wort boiling to avoid aroma volatilization and thereby impart strong hop-derived aromas. However, previous studies have demonstrated that despite the volatilization effects of boiling wort, hops that are added early in the kettle boil can contribute to hop aroma. Nonvolatile hop-derived precursors, specifically glycosides, may survive the boiling process and become hydrolyzed to release volatile aglycones capable of contributing to aroma. To investigate the contribution of these different hop fractions to the aroma of kettle-hopped beers, 12 single-hopped pilot-scale (3 hL) beers were brewed using pellet, supercritical CO2 extract, and spent hop fractions of Citra, Simcoe, Centennial, or Cascade cultivars. Pellet, extract, and spent additions consisted of a single hop addition 5 min into a 60 min boil. Volatile analysis of beers was performed using stir-bar sorptive extraction and quantified using gas chromatography–mass spectrometry. Beers were analyzed for the common terpenoid compounds α-pinene, β-pinene, β-myrcene, limonene, linalool, E,β-caryophyllene, α-humulene, and α-terpineol. In addition, beers were evaluated using descriptive sensory analysis. The descriptive sensory data identified significant differences among the cultivar and hop product treatments. The spent hop treatments produced beers that had a noticeable hop aroma, which suggests that the water-soluble components left behind in the spent hops may contribute to hop aroma in beer. The intensity and nature of the hop aroma in the spent treatments were hop variety specific. However, the contributions of water-soluble components found in spent hops to increased aroma intensity in beer were small, especially compared with the pellet and extract treatments.

Keywords: Stir-bar sorptive extraction, Spent hops, Gas chromatography–mass spectrometry, Glycosides, Descriptive analysis, CO2 extract