R. A. HOTCHKO (1), T. H. Shellhammer (1); (1) Oregon State University, Corvallis, OR, U.S.A.

Raw Materials
Thursday, June 5 - 2:00 p.m.-3:45 p.m.
Level 4, Red Lacquer Ballroom

Heavily hopped beer, produced through various dry-hopping regimes, is sometimes described as possessing pleasant coconut, apricot, and peach aromas. It is hypothesized that lactones are responsible for these aromas, so it is of interest to determine the impact of specific hop-derived aroma compounds. Relatively little research has been published that identifies the presence and quantifies the levels of these compounds in highly hopped beer. Lactones possess a carbon ring with oxygen atoms derived from the intramolecular esterification between a hydroxy and carboxy group on a hydroxyl fatty acid. This lactonization occurs in the yeast peroxisome, and it is thought that a potential source of hydroxyl fatty acids could be from hop degradation products. These hydroxyl fatty acids are transformed into the aforementioned stone and tropical fruit aromas when in contact with active yeast, usually during the final stage of fermentation or during the dry-hopping process. Structural differences in the lactones not only produce different pleasant aromas but also influence aroma quality and detection thresholds. The levels of 4 and 5 membered rings, gamma- and delta-lactones respectively, with saturated lateral chains ranging from 5 to 7 carbons have not been fully recorded in dry-hopped beers. This study evaluated the levels of four lactones, gamma- and delta-decalactone, and gamma- and delta-dodecalactone, in commercially produced dry-hopped beers utilizing solid-phase microextraction (SPME) and GC-FID to quantify levels based on an internal standard.

Rachel Hotchko is currently working toward her M.S. degree in food science and technology, with an emphasis in brewing science, under Thomas Shellhammer at Oregon State University. She received a B.A. degree in biochemistry from St. Mary’s College of Maryland in St. Mary’s City. After graduation from St. Mary’s in 2010 she worked for two years at Hopunion, LLC in Yakima, WA—first as a hop chemist technician, then as the hop lab supervisor. During her graduate work at OSU, she was awarded an ASBC Graduate Student Scholarship and worked as an intern in the research and development lab at Sierra Nevada Brewing Co., where she explored aroma compounds in whole-cone hops and beers with SPME and GC-MS-O.