P-36 - Aldehyde Scavenging in Very-low Alcohol Beers: A Quantitative Analytical Look at Beers Produced Using Maltose-negative Saccharomyces Cerevisiae

The use of arrested fermentation is a viable method of very low-alcohol beer production (i.e. beers containing around 0.5% ABV). A common means of arrested fermentation is through a combination of low gravity wort and non-traditional (non-Saccharomyces) maltose-negative yeasts such as Saccharomycodes ludwigii, Zygosaccharomyces rouxii, Hanseniaspora uvarum, and Pichia kudriavzevii. While non-conventional yeasts offer unique flavors, their lack of metabolic hallmarks associated with domesticated Saccharomyces cerevisiae may negatively impact the flavor development of low-alcohol beers.

Aldehyde and carbonyl compounds that accumulate during the mashing and fermentation process will typically be scavenged and reduced during normal fermentation with domesticated Saccharomyces cerevisiae. However, during arrested fermentation, aldehyde side-products and carbonyl compounds may not have the necessary time – and in the case of non-traditional yeasts - available metabolic pathways to be significantly reduced, potentially resulting in undesirable flavors and aromas of the final product.

This study evaluated key metabolic byproducts of three genetically distinct and domesticated maltose-negative Saccharomyces cerevisiae strains (SC1, SC2, SC3) and one “wild” non-Saccharomyces species: Saccharomycodes ludwigii (SL1). The four selected strains were fermented in near-identical worts (OG 7.55°P ±0.15, pH 4.59). Four low-alcohol beers (0.64 ± 0.01% ABV) were produced at 20 L scale and fermented at 20°C for 162 hours. The beers were conditioned for two weeks at 0.5°C in contact with the yeast. The beer was collected, pasteurized, and analyzed. A multifactor aroma profile analysis of fresh and forced-aged beers revealed that the beers produced by the different strains were comparable, with minor flavor differences. Notably, SC1 and SC3 exhibited the presence of POF, while SL1 was characterized by a unique honey-like aroma. Quantitative chemical analysis revealed strong similarities in aldehyde composition among all four beers, but significant differences were observed in hexanal (grassy, green), 2-methylpropanal (pungent aldehydic), furfural (almond), and phenylethanal (pungent, lilac, honey) concentrations in beer fermented with SL1, which were 84%, 40%, 54%, and 47% higher than the average concentrations, respectively.