Tim Wallen is currently an analytical chemist at Hoptechnic®, a subsidiary of Virgil Gamche Farms, Inc. in Toppenish, WA.
Tim recently graduated with an MS in Chemistry in May 2019 under the guidance of Dr. Jerry Troutman studying complex glycan synthesis in bacteria developing high performance liquid chromatography – mass spectrometry (HPLC-MS) methodology. Before that he had an ORISE research fellowship at the CDC in the clinical chemistry branch in the lipid reference laboratory setting research measurement standards utilizing GC-MS. He originally graduated in 2011 with a BA in chemistry with ACS certification at Hendrix College in Conway, AR where he did research studying Binturong (Asian Bear Cat) volatiles under Dr. Tom Goodwin utilizing solid phase dynamic extraction (SPDE) GC-MS in a collaboration with Dr. Christine Drea of the Duke University Primate Center. During this time, he has been an avid homebrewer for 8 years and is a certified BJCP homebrew judge.
August 24th, 2020 | 38 mins 40 secs
A growing demand in utilizing biotransformation, a general term for the conversion of compounds through biological pathways, to improve the organoleptic profile of beer has changed the way hop forward beer recipes are approached. While the analysis of terpene biotransformation has been well documented, there remains a gap in knowledge in sulfur compounds due to their extremely low concentrations (sometimes in concentrations of parts per trillion) and high volatility. Analysis of sulfur compounds requires precise and sensitive analytical methodology in order to detect them. While sulfur compounds have been successfully detected using gas-chromatography mass spectrometry (GC-MS) a pulsed flame photometric detector (PFPD), and a GC sulfur chemiluminescence detector (GC-SCD), the research presented here utilizes a GC-SCD via stir bar-sorptive extaction (SBSE) methodology previously used to track aroma intensities in optimizing harvest picking windows. This work shows an identification of various thiols and sulfur compounds found in both un-hopped and hopped wort (with Amarillo® (VGXP01), Cashmere, Idaho grown Saaz (Osvald-72 c.v.), and Czech Saaz) and tracks them through the fermentation process confirming the volatility of some thiols and most notably the presence of 4-methyl-4-mercaptopentan-2-one (4MMP) in the final beer at a retention time of 9.5 minutes, a compound that contributes a catty, black currant/Sauvignon Blanc aroma character. Differences in hop varieties were compared with an American ale yeast, and the effect of yeast strain as well as temperature on thiol production with VGXP01 was compared between an American ale, German lager, Belgian saison, and Brettanomyces bruxellensis strain.