Metschnikowia pulcherrima in mono or co-fermentations in brewing

Metschnikowia pulcherrima, also known as Candida pulcherrima (anamorph), is a non-Saccharomyces yeast, well known from the wine industry. It is currently used in sequential or co-fermentation with Saccharomyces cerevisiae to enrich the wine with more complex and varietal aromas. In this study, we examined the potential application of a commercial M. pulcherrima strain in the brewing industry. First, the fermentation dynamics in glucose, fructose, and maltose, at 13 and 20 degrees C, were studied, and GC-MS analysis of the volatile compounds related to beer flavour was performed. After being assured that M. pulcherrima is capable of metabolizing maltose, the main wort sugar, a Pale Ale beer was produced at 13 and 20 degrees C. A pure M. pulcherrima and two mixed cultures of S. cerevisiae with M. pulcherrima in ratios of 1:1 and 1:10 were used, and fermentation was monitored by specific gravity and free amino nitrogen measurements. The ethanol content at the end of fermentation varied within 4.0 - 5.5 % (v/v). The volatile profile analysis of the produced beers revealed the presence of higher alcohols, medium-chain fatty acids and their esters, with the obtained results presenting satisfactory complexity in flavour.