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.