Growth and Fermentation Performance of Two Wild Strains of Torulaspora delbrueckii for Low-Alcohol Beer Production

Abstract

Two wild strains of Torulaspora delbrueckii were isolated from the bark of a native White Oak (Quercus alba) tree near the North Carolina Arboretum in Asheville. Yeasts from the genus T. delbrueckii have been previously reported colonizing a wide variety of habitats; however, despite the relative abundance of this species, there is still no consensus on its fermentation behavior and suitability for the production of a palatable beer. Typically, T. delbrueckii strains are not capable of utilizing maltose efficiently and cannot complete fermentation to elevated levels of alcohol. However, in beer fermentation, T. delbrueckii can influence aromatic profiles in the brewing process, transforming hop aroma terpenoids and increasing the levels of ethyl hexanoate and ethyl octanoate. Two new wild strains, collected in western North Carolina and designated as C2B1 and HLB1, demonstrated outstanding fermentation performance on simple glucose media, achieving in excess of 5% ABV, but performed poorly in malt extract media, achieving only 1–2% ABV. Based on a preliminary evaluation, taste panel results indicate these wild strains could be used in the production of acceptable low-alcohol beers from an all-malt wort.