Screening of volatile organic compounds produced by yeasts from a brazilian yeast culture collection (CCMA) and selection of yeasts for the production of mead

Abstract

Yeast culture collections harbor great genetic and phenotypical diversity that can be explored to identify strains that demonstrate an exceptional suitability for specific biotechnological applications. One such application is bio-flavoring, in which yeasts are utilized to enhance the aroma profile of fermented foods and beverages. In the first part of this study, a screening of the production of volatile aroma compounds by yeast isolates (n = 63) from the CCMA (Coleção de Culturas da MicrobiologiaAgrícola) was carried out. The purpose was to select strains that have potential for application as bio-flavoring agents in mead fermentations. Strains were grown on culture medium and volatile organic compounds were identified by gas chromatography – mass spectrometry. This screening identified several strains that produced aroma compounds of interest that represent floral and fruity aromas. Clustering of yeasts by aroma profile enabled the selection of strains that produce aroma compounds in amounts that are relevant for food fermentations (n = 19). While several strains that produced attractive aroma profiles were not able to grow on honey must, seven yeast strains were able to produce a sweet, low-alcoholic mead (45-168 g/l of residual sugar, 3.8-6.5% ethanol v/v) with distinct aroma profiles. In the second part of this study, four strains (Saccharomyces cerevisiae CCMA 1523, Pichia jadinii CCMA 0160, TorulasporadelbrueckiiCCMA 1524 and Kluyveromyceslactis CCMA 1518) were selected for larger scale mead fermentations, as single cultures or co-cultures of S. cerevisiae and each of the other yeasts individually. Among other parameters, consumption of sugars, production of ethanol and organic acids in the meads were determined. An untrained tasting panel evaluated the intensity of selected taste and flavor attributes and hedonic appreciation. In both single strain and mixed strain fermentations with S. cerevisiae, meads produced with either T. delbrueckiior K. lactishad a roughly three-fold higher content of honey-aroma compound phenethyl acetate. Meads produced with T. delbrueckii had the highest acceptance rate, followed by meads produced with K. lactis. Also meads produced with mixed cultures containing these strains had higher acceptance rates than those produced with only S. cerevisiae. Moreover, the sensory panel expressed a preference for low-alcoholic meads with high residual sweetness. The results demonstrate the potential of non-conventional yeasts to improve the aroma profile and sensory qualities of low-alcoholic meads.