Reduction of Perceived Mercaptan via Fermentor Trub Removal

Joseph Spearot and Micah Krichinsky. Dogfish Head Craft Brewery, Milton, DE, U.S.A.
Due to increased competition in the industry, off-flavors and negative experiences can be extremely detrimental to brand success. Sulfur compounds, including the particularly offensive mercaptan, should be controlled for and limited in final beer products. Mercaptan, smelling like drains or rotting garbage, may come from yeast autolysis, bacterial infection, formation during maturation, or dry-hopping. Although previous methods such as filter pads and using additional chemicals to remove these compounds have been used, none are particularly cost effective or safe for production breweries. One way to reduce perceived mercaptan is to increase the sedimentation of materials in the fermenter after filling. By reducing contact time with hop material, and thus sulfur compounds, the overall levels of perceived mercaptan should also decrease. The following study was conducted to determine the impact that hop material has on the presence of mercaptan and whether removal of these materials serves as a viable method to limit the sensory impacts of mercaptan. Additional material was removed from the cone of cylindroconical fermentation vessels at 12 and 24 h after fermentation began to reduce overall contact time. Samples from both the fermentor and bright tank trials were rated significantly lower (P < 0.05) for mercaptan and sulfur and higher in overall liking in some cases. This method may be utilized in the future for commercial breweries to limit the levels of mercaptan in finished beer. Future studies should investigate the contribution of aeration rates, yeast strains, and aging conditions on mercaptan levels.

Keywords: Mercaptan, Sulfur, Sensory, Off-flavor, Trub