Use of non-conventional yeasts for enhancing the sensory quality of craft beer

In recent years, craft beer production has grown significantly, sparking interest in using non-conventional yeasts to produce beers with distinctive flavors. This work investigated the impact of unconventional yeast strains, including Hanseniaspora uvarum YGA34 (EP1), Lachanchea thermotolerans MNF105 (EP2), Candida oleophila YS209 (EP3) and Starmerella lactis-condensi MN412 (EP4), as innovative co-starter cultures alongside the widely used Saccharomyces cerevisiae US-05 . The control trial was inoculated with S. cerevisiae US-05 (TC) alone. For the first time, C. oleophila and St. lactis-condensi have been applied for beer production and also result have been compared with H. uvarum and L. thermotolerans. These strains, selected from high-sugar matrices such as manna and fermented honey by-products, exhibited logarithmic growth cycles of 5-8 during fermentation. Starmerellalactis-condensi MN412 and L.thermotolerans MNF105 efficiently consumed fructose, glucose, and sucrose in beer must before the addition of S. cerevisiae US-05, with L.thermotolerans also effectively consuming maltose. The highest glycerol content (3.36 g/L) was observed in the EP4 trial with St. lactis-condensi MN412. Esters were the dominant volatile compounds in all samples (91.2-237.3 mg/L), with the EP2 trial showing the highest ester content (237.3 mg/L), primarily due to ethyl octanoate (125.5 mg/L). EP2 also had the most favourable sensory profile, excelling in 10 attributes, while other beers showed notable performances. These unconventional yeast strains exhibited significant differences compared to beers brewed with S. cerevisiae alone. Additionally, their application led to an increase in volatile organic compounds. In conclusion, novel yeast strains isolated from high-sugar matrices showed excellent technological properties, making them promising co-starters and starter in innovative craft beer production.