New Approaches for the Fermentation of Beer: Non-<i>Saccharomyces</i> Yeasts from Wine

Non-<i>Saccharomyces</i> yeasts represent a very attractive alternative for the production of beers with superior sensory quality since they are able to enhance the flavour of beer. Furthermore, they can produce beers with low ethanol content due to the weak fermentative capacity of a large percentage of non-<i>Saccharomyces</i> species. The objective of this study was to evaluate the ability of 34 non-<i>Saccharomyces</i> yeast strains isolated from Madrilenian agriculture to produce a novel ale beer. The non-<i>Saccharomyces</i> yeast strains were screened at two scales in the laboratory. In the first screening, those with undesirable aromas were discarded and the selected strains were analysed. Thirty-three volatile compounds were analysed by GC, as well as melatonin production by HPLC, for the selected strains. Thirteen strains were then fermented at a higher scale in the laboratory for sensory evaluation. Only yeast strains of the species <i>Schizosaccharomyces pombe</i> and <i>Lachancea thermotolerans</i> were able to complete fermentation. Species such as <i>Torulaspora delbrueckii</i>, <i>Metschnikowia pulcherrima</i>, <i>Wickerhamomyces anomalus</i>, <i>Hanseniaspora vineae</i>, and <i>Hanseniaspora guilliermondii</i> could be used both for production of low ethanol beers and co-fermentation with a <i>Saccharomyces</i> yeast to improve the organoleptic characteristics of the beer. In addition, for these strains, the levels of melatonin obtained were higher than the concentrations found for <i>Saccharomyces</i> strains subjected to the same study conditions. The selected strains can be used in future trials to further determine their viability under different conditions and for different purposes.