Abstract
Biodiversity of native yeasts, especially in winemaking, has hidden potential. In order to use the value of non-Saccharomyces strains in wine production and to minimise the possibility of its deterioration, it is necessary to thoroughly study the yeast cultures present on grape fruits and in grape must, as well as their metabolic properties. The aim of the study was to characterise the yeast microbiota found during spontaneous fermentation of grape musts obtained from grape varieties ‘Rondo’, ‘Regent’ and ‘Johanniter’. Grapes from two vineyards (Srebrna Góra and Zadora) located in southern Poland were used for the research. Succession of subsequent groups of yeasts was observed during the process. Metschnikowia pulcherrima yeasts were identified both at the beginning and the end of the process. Hanseniaspora uvarum, Wickerhamomyces onychis and Torulaspora delbrueckii strains were also identified during the fermentation. Torulaspora delbrueckii and Wickerhamomyces onychis strains were identified only in grape musts obtained from grapes of the Zadora vineyard. These strains may be characteristic of this vineyard and shape the identity of wines formed in it. Our research has provided specific knowledge on the biodiversity of yeast cultures on grapes and during their spontaneous fermentation. The research results presented indicate the possibility of using native strains for fermentation of grape musts, allowing to obtain a product with favourable chemical composition and sensory profile.
Highlights
Grape must is a rich environment for various yeast species
The number of yeasts during spontaneous fermentation of grape musts remained at a similar level for all analysed grape varieties in 2014
In 2013, there were a smaller number of yeasts, in average by 4–5 logarithmic rows (Figs. 1 and 2). It could be caused by a small amount of food resources present in the fermenting medium in 2013, which probably limited the growth of microorganisms
Summary
Grape must is a rich environment for various yeast species. Fermentation process is related to several mechanisms, including metabolism of sugars and nitrogen compounds contained in grape must, enzymatic hydrolysis of grape components, yeast cell autolysis and bioadsorption of individual must components. Studies show high biodiversity of yeast microorganisms during the first 24–72 h of the process (Zott et al 2008; Ocón et al 2010). Factors such as mechanical damage of berries, agronomic practices and terroir (soil type, average annual temperature, rainfall) directly affect the biota of yeasts present on the surface of grapes (Barata et al 2012; Díaz et al 2013; DrumondeNeves et al 2016; Grangeteau et al 2017)
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