Analytical Session
Peter H Wolfe, Oregon State University
Co-author(s): Thomas Shellhammer and Michael Qian, Oregon State University, OR, USA
ABSTRACT: The rate of hop aroma compounds extracted from
Cascade hops during dry hopping was studied using both an unhopped beer
and a model beer system devoid of malt and yeast aromas. Cascade hops
pelletized by four different processors yielded different particle size
distributions and pellet densities. These pellets, as well as whole
hops, were dosed into a degassed medium (water, 6% [v/v] ethanol, pH
4.2), and the hop aroma extraction was measured periodically over a 1
week period. Solid phase micro-extraction (SPME) followed by gas
chromatography (GC-FID) was used to analyze the levels of aroma
compounds in the extraction medium. Variation in hop pellet physical
properties did not significantly impact the extraction rate of hop
volatiles such as linalool, geraniol, limonene, and myrcene, with one
exception. One treatment showed an increased absolute concentration of
geraniol. Separately, dry hop aroma extraction was measured over a short
time (1 day) at room temperature in the unhopped beer. Irrespective of
the hop form (whole or pellet), the concentrations of hydrocarbon
terpenes peaked between 3 and 6 hr and subsequently declined, while the
concentrations of terpene alcohols continued to increase throughout the
24 hr dry hop extraction. The rate of hop aroma extraction appeared to
be significantly influenced by hop pellet properties and occurred rather
rapidly regardless of hop form.
Peter Wolfe received a B.S.
degree in physiology from the University of Oregon in 2007. After
graduation, he worked as a researcher at the University of Oregon,
publishing work on construction ergonomics. He began working toward a
master’s degree at Oregon State University in 2010 in the Food Science
and Technology Department. Working under Tom Shellhammer, his work
focuses on hop aroma in beer and aroma extraction during the dry-hopping
process.
