Tom Boudreau (1), Sihui Ma (1), Nicholas Patrick (1), Amanda Stewart (1); (1) Virginia Tech, Blacksburg, VA, U.S.A.
Yeast, Fermentation, and Microbiology
The cider industry is growing rapidly in the United States, with cider makers becoming increasingly concerned with forming specific fermentation methods to optimize cider fermentations and product quality. Yeast assimilable nitrogen (YAN) is known to significantly impact hydrogen sulfide (H2S) production and fermentation kinetics during wine and beer fermentation but has not been extensively studied in cider fermentations. Nitrogen-deficient apple juice was supplemented with asparagine, arginine, methionine and ammonium and fermented with two yeast strains. There was no difference in H2S production between sources of nitrogen added as asparagine, arginine, and ammonium. Additions of methionine decreased H2S production at concentrations as low as 5 mg/L in nitrogen-deficient juice in one yeast strain, but only high concentrations of methionine decreased H2S production when juice was supplemented with moderate YAN concentrations, and methionine did not influence H2S production at high YAN concentrations. When juice was supplemented to 153 mg/L of YAN there was an increase in H2S production regardless of methionine treatment. H2S production decreased when juice was supplemented to 253 mg/L of YAN. Following sensory evaluation, panelists were able to discern differences in the aroma of samples supplemented with ammonium and methionine, which corresponds to an increase and decrease in H2S production during fermentation, respectively. These novel findings indicate moderate YAN concentrations may lead to a large increase in H2S production that is detectable by consumers, but that methionine may be a key nutrient in preventing H2S production during fermentation. This study is essential for the continued development of ideal fermentation strategies to produce high-quality ciders.
Tom Boudreau is a graduate student at Virginia Tech studying fermentation sciences and technology in the Department of Food Science and Technology. He previously earned a B.S. degree in food science and human nutrition from the University of Florida and worked as a product development and quality control technician in the food industry. Tom’s primary research is in hard-cider fermentation, regarding cider chemistry, nutrient consumption during fermentation, and final cider chemical and sensory quality. He also conducted research in brewing sciences, specifically the chemical and sensory properties of bottled beers as a result of various storage conditions. Tom’s continued research is in the fields of wine, cider and beer fermentation as it relates to final product chemical and sensory quality.