Evaluation of indigenous non-Saccharomyces cider yeasts for use in brewing

The non-Saccharomyces yeasts represent a great richness for the production of new and different types of beers. In this study, the role of eight yeast strains (Saccharomycodes ludwigii, Metchnikowia pulcherrima, Hanseniaspora uvarum, Hanseniaspora osmophila and Brettanomyces bruxellensis) isolated from Asturian cider and belonging to five unconventional species was evaluated. None of the strains could ferment the main wort sugars (maltose and maltotriose). Beers produced by S. ludwigii strains showed the highest ethanol content (21.6 g/L) and interestingly high levels of fusel alcohols, fatty esters and isoamyl acetate. Strains of B. bruxellensis were the only ones that produced ethyl phenols and they also generated the highest concentration of fatty acids and their ethyl esters. Sucrose was not utilised by Metschnikowia and Hanseniaspora strains, resulting in low ethanol formation (4.7 g/L), although these yeasts differed in terms of their synthesis of volatile compounds. Larger amounts of fatty acid esters were detected in beers fermented by H. osmophyla 10, while H. uvarum 62 produced more 2-phenylethyl acetate and ethyl acetate. M. pulcherrima 301 stands out for its low fermentative capacity and production of volatile compounds. These results show the interest of non-Saccharomyces strains in the production of beers with low alcohol content and their potential use in developing new beer styles in sequential or mixed inoculations with S. cerevisiae strains.