Functional screening of non-Saccharomyces yeasts from grape must, manna, and honey for wine colour stability and aroma modulation

Abstract

Ensuring colour stability in red wines represents a major technological and commercial challenge for the wine industry. Wine colour stability is influenced by biochemical and physical interactions between yeasts and anthocyanins during fermentation [1]. In addition to conventional fermentative traits, non-Saccharomyces yeasts may contribute to colour preservation or depletion depending on strain-specific characteristics such as anthocyanin adsorption, β-glucosidase activity [2], and hydroxycinnamate decarboxylase (HCDC) activity [3]. In this study, 163 non-Saccharomyces strains obtained from spontaneously fermenting grape must, manna, and honey were screened for oenological potential. Following a preliminary selection process based on ethanol tolerance (≥ 4 % v/v), potassium metabisulfite resistance (100–250 mg/L), and low H₂S and acetic acid production, 52 indigenous strains were retained and characterised together with five reference strains (57 strains in total). Anthocyanin adsorption was assessed on YEPD agar supplemented with grape-derived anthocyanins (pH 3.5). β-Glucosidase activity was evaluated using an esculin-glycerol agar assay (halo-based semi-quantitative classification). HCDC activity was determined on YEPD agar supplemented with p-coumaric acid. Marked strain-dependent variability was observed for all colour-related traits. Anthocyanin adsorption ranged from absent to high, with Metschnikowia pulcherrima and Hanseniaspora uvarumpredominantly showing high adsorption, whereas Lachancea thermotolerans displayed mainly medium adsorption. Of the 57 strains analysed, 11 showed no detectable β-glucosidase activity, whereas most isolates exhibited medium to strong activity. HCDC activity was highly prevalent in H. uvarum, M. pulcherrima, and L. thermotolerans, whereas it was absent in Starmerella spp. and Citeromyces matritensis. The combined evaluation of adsorption and enzymatic traits emphasises the relevance of strain-level selection to balance aroma enhancement and colour preservation. Several strains, particularly within L. thermotolerans, exhibited balanced combinations of adsorption and enzymatic activities, underscoring the importance of strain-level selection for targeted red winemaking strategies aimed at enhancing colour stability and sensory complexity. These findings support targeted strain-level selection as a biotechnological approach to optimise colour preservation and aroma potential, with relevance for industrial red wine product

References

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