November 22nd, 2021 | 44 mins 44 secs
Why does dry-hopping during active fermentation change sensory profiles? Is the black box of biotransformation really what drives those changes or is it something else entirely?
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.
June 8th, 2020 | 35 mins 45 secs
Biotransformation has become a buzzword in the brewing community, with many brewers even performing dry hopping at certain specific times to hit what is considered to be the “biotransformation sweet spot.” Academic literature does not support these claims. With the aid of enzymes developed for the wine industry, two experimental IPA beers were brewed: one with an enzyme preparation aimed at hydrolyzing glycosides and the other with a β-lyase preparation aimed at releasing bound thiols. Triangle tests for each treatment were carried out by a panel of over 25 participants, composed of brewers and judges, and showed that both beers were significantly different from the control, yet preference was overwhelmingly toward the no-enzyme IPA control beer. Furthermore, the descriptive analysis carried out by the same panel showed a clear trend toward both enzyme beers being less tropical/fruity and more herbal and/or citrusy, the exact opposite of the purported benefit of biotransformation.
February 4th, 2019 | 26 mins 24 secs
Eric Abbott talks about the biotransformation of hops - How it works, how to maximize it, and more.