Technical Session 01: Hops I Session
Thomas H Shellhammer, Oregon State University, Corvallis, OR, USA
Co-author(s): Daniel Sharp, Yanping Qian, and Michael Qian, Oregon State University, Corvallis, OR, USA
ABSTRACT: Hop aroma in beer is complex. While hop oils
contain over 300 different components that can contribute to beer
flavor, their high volatility results in little hop oil being retained
in the finished beer. Yet beers produced using a long boil do have
significant hop flavor and aroma. While terpene alcohols and oxidation
products (epoxides) can contribute flavor, another hypothesized source
of this aroma lies in glycosidically bound aromatic compounds such as
glucosides and arbinoglycosides of alcohols, monoterpene alcohols, and
ketones. During fermentation, and more likely post-fermentation, yeast
may hydrolyze the sugar moieties for energy and, thereby, release the
volatile aglycone, thus contributing to hop aroma in beer. This study
examined the impact of the water-soluble fraction from four different
American hop varieties (Simcoe, Centennial, Citra, and Cascade). Samples
of each variety were extracted using supercritical fluid CO2
extraction, and the resultant extract and spent materials (along with
the starting material) were dosed at (1 g/L) in hot wort to produce
approximately 40 L of finished beer. Volatile analysis of beers was
performed using a stir bar sorptive extraction (SBSE) with compound
identification via GC-MS-FID. Key aroma compounds, alpha-pinene,
beta-pinene, myrcene, limonene, linalool, caryophyllene, humulene, and
terpineol were identified using selective ion monitoring mode and
quantified. The linalool concentrations in the spent hopped beers were
significantly higher than the other two treatments and were high enough
to contribute to hop aroma. Principal component analysis revealed
clustering of beers into separate groups by type of hop material
(pellet, extract and spent). The sensory descriptive data identified
prominent differences among the form and variety treatments. The spent
hop treatments produced beers that had perceptible hop aroma. In one
instance, Simcoe, the spent treatment resulted in beers that had higher
aroma than extract and pellet treatments from other varieties. The
intensity and nature of the hop aroma in the spent treatments was
hop-variety specific, making it difficult to make a blanket statement
regarding the water-soluble components of hops and their impact on hop
aroma across all varieties. Nonetheless, there is sufficient evidence
that in Citra and Simcoe hops the spent material contains substantial
hop aroma or precursors thereof. These results point to the importance
of non-oil contributions to hop aroma in some varieties.
Thomas
Shellhammer is the Nor’Wester Professor of Fermentation Science in the
Department of Food Science and Technology at Oregon State University,
where he leads the brewing science education and research programs. His
brewing research investigates hops and beer quality. He directs the
brewing education component of the Fermentation Science program at OSU
and teaches courses about brewing science and technology and beer and
raw materials analyses, as well as an overview of the history, business,
and technology of the wine, beer, and spirits industries. Tom received
his Ph.D. degree from the University of California, Davis, in 1996.
During the 2008–2009 academic year, while on sabbatical leave from OSU,
he worked at the Technical University of Berlin as a Fulbright Scholar
and Alexander von Humboldt Fellow. Tom is a member of the Board of
Examiners for the Institute of Brewing and Distilling, London, England,
and the chair of the Editorial Board of the MBAA Technical Quarterly.
VIEW PRESENTATION 4
