Impact of indigenous non-Saccharomyces yeasts on early volatile fermentation metabolites of white Maraština grape must

Non-Saccharomyces yeasts play a significant role in wine fermentation by contributing to the production of metabolites which increase the complexity of the wine's aromatic profile. The objective of this study was to provide insight into the production of metabolites in the early phase of fermentation by indigenous non-Saccharomyces yeast isolates. The yeasts were previously isolated from Maraština grapes, including Metschnikowia pulcherrima, Metschnikowia chrysoperlae, Metschnikowia sinensis/shanxiensis, Pichia kluyveri, Hanseniaspora uvarum, Hanseniaspora guilliermondii, and Lachancea thermotolerans yeasts. To elucidate the specific role of each isolate and to exclude the impact of other microorganisms, the yeasts were inoculated into sterile Maraština grape juice. The concentration of volatile compounds and primary fermentation metabolites produced by the investigated yeasts were compared with those produced by commercial L. thermotolerans and M. pulcherrima strains. Fermentation kinetics were monitored using Fourier transform infrared spectroscopy, and volatile compounds were analyzed using solid-phase microextraction and gas chromatography coupled to a mass spectrometer. Investigated indigenous non-Saccharomyces yeast increase the concentration of volatile compounds belonging to the groups of terpenes, C13-norisoprenoids, alcohols, esters, ketones and lactones in early ferments. P. kluyveri exhibited significantly the highest concentration of esters and β-damascenone. Furthermore, M. chrysoperlae and M. sinensis/shanxiensis represent unexplored species for improving the oenological potential of grape variety by producing higher concentrations of esters. All indigenous yeasts produced lower concentrations of acetic acid and acetaldehyde compared to the control strains. These results highlight the impact of indigenous non-Saccharomyces yeasts on early fermentation aromas and essential metabolites, thereby contributing to the enhancement of wine.