Technical Session 01: Hops I Session
Patricia M Aron, MillerCoors, Milwaukee, WI USA
Co-author(s): Thomas Shellhammer, Oregon State University, Corvallis, OR, USA; David Ryder, MillerCoors, Milwaukee, WI, USA
ABSTRACT: The most important class of polyphenols for
consideration in beer and related products is that of the
2-phenylbenzopyrans, generally referred to as flavonoids. In contrast to
the roles of other hop derived ingredients, such as the isomerized
alpha-acids and their reduced products (bittering acids), the absolute
value of hop derived flavonoids is not well realized. To add to the
confusion, very little is understood regarding the fate of these
polyphenols during the brewing and aging processes. During this
experiment lager beers were produced using varying hopping regimes to
investigate hop product contribution to beer polyphenol content.
Finished beers were also force-aged and monitored for changes in
polyphenolic profiles. Polyphenol rich extracts were produced from the
beers using Sephadex LH20 resin. Finished beers varied in total
polyphenols, flavanoids, and proanthyocyanidins by hopping regime.
Phloroglucinolysis was used in conjunction with RP-HPLC-ESI-MS to reveal
subunit composition and proanthocyanidin mDP. Six major
phloroglucinolysis products were observed; however, galloylated
flavanols were not detected in any of the beers. The predominant
subunits by molar ratio were (+)-catechin followed by
(–)-epigallocatechin; however, beers brewed with hop solids were also
high in (–)-epicatechin. The major extension subunit was (+)-catechin
for all treatments. Although Sephadex extracts produced from the beers
were phenolic in nature, proanthocyanidins only accounted for up to 2%
of the total phenolic material. Total flavanoid and proanthocyanidin
content of the beers increased initially during storage, with eventual
decreases occurring after 6 weeks of storage at 30°C. Beers high in hop
polyphenols did not suppress the loss of iso-alpha-acids during aging
and were also assessed as the least flavor stable of the beers test by
ESR T150. Conversely, the presence of hop polyphenols suppressed the
formation of staling aldehydes during aging as measured by SPME-GC-MS.
Pattie
Aron received a B.S. (2000) degree in biochemistry from Elmira College,
Elmira, NY, and further obtained both M.S. (2007) and Ph.D. (2011)
degrees in food science and technology from Oregon State University,
Corvallis, OR. In February 2010 she began employment as an intern at
MillerCoors as a hop chemist in applied brewing technology in the
Technical Center in Milwaukee, WI. Following completion of her Ph.D.
degree, Pattie continued on at MillerCoors, where she functions as a hop
scientist and continues to conduct research for applied brewing
applications.
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