Evaluation of Two Brewer’s Yeast Strains throughout Serial Re-Pitching in Beer Fermentation
Eric Melgar, Tyler Schneider, Melissa Hayes, Anna Belle Kratz, and John Michael McCranie.
Beer is a fermented drink primarily made from yeast, hops, water, and grains. In order to spread the cost of the yeast culture over many brews and to maintain a consistent flavor profile in certain beers, brewers commonly harvest and re-pitch yeast. Ideally, brewers should be able to reuse yeast for at least 7 generations and often as many as 10 generations if good harvesting and storage practices are followed. This experiment analyzed second and third generation brewer’s yeast strains’ cell counts collected from three beers: (1) a beer brewed with a single Pacific Ale yeast slurry, (2) a beer brewed with a single Irish Ale yeast slurry, (3) a beer brewed with a combination slurry containing second generation Pacific Ale and Irish Ale yeast strains, and (4) a beer brewed with a combination slurry containing third generation Pacific Ale and Irish Ale yeast strains. The Pacific Ale (WLP041) and Irish Pale Ale (WLP004) yeasts were purchased from White Labs in Asheville, NC. It was then hypothesized second and third generation yeast cell counts harvested from the single strain beers (1) and (2) would have higher cell counts than the second and third generations from the blended beers (3 and 4) due to competition of the two strains. However, the results of the study showed there was not a significant difference between the yeast cell counts harvested from the single strain beers (1) and (2) as compared to the yeast cell counts harvested from the second and third generations of the blended beers (3 and 4).
Eric Melgar is a junior biology major with a minor in chemistry. He plans to attend medical school after graduating from Lander.
Tyler Schneider is a senior biology major with a minor in chemistry. He is a member of the TriBeta National Biological Honor Society. Tyler plans to attend osteopathic medical school after graduating from Lander.