Characterization of Wine Yeasts during Wine Process using Different Techniques

Abstract

Study of the microorganisms that colonise the skin of grapes has been an important topic in microbial taxonomy of especially yeasts associated with vines and vineyards. It is known that yeast microbiota on grapes and in musts is influenced by factors such as climatic conditions, geographical location of the vineyard and grape variety. Molecular methods have been used for the identification of yeasts from wines and the most relevant molecular methods used in the identification of yeast species are based on the variability of the ribosomal genes 5.8S, 18S and 26S. Previous results have demonstrated that the complex ITS regions (non-coding and variable) and 5.8S rRNA gene (coding and conserved) are useful in measuring close fungus phylogenetic relationships. Mid-infrared spectroscopy is a rapid technique which provides highly specific biochemical fingerprints of microorganisms and coupled with different chemometrics analyses offer a wide range of applications including detection, taxonomic level classification and characterization. The objective of this study was identification of yeast flora of 7 wine samples (red, rose and white) through entire wine process from must until the end of fermentation using molecular methods in comparison with cultural methods followed by mid-IR spectroscopic techniques to monitor the diversity of yeasts during a wine process. As a result, identified yeast species included M.pulcherrima (2/19, 11%), P.membranifaciens (3/19, 16%), H.uvarum (1/19, 5%) and S.cerevisiae (13/19, 68%) during the whole process. Multivariate analysis of the data showed that S.cerevisiae isolates formed a cluster which were probably starter cultures and this cluster was generally separated from the other three yeasts which were isolated at the beginning of wine process. Therefore, it was concluded that FTIR could be succesfully used as a complementary method of molecular techniques for differentiation of wine yeast species isolated at different steps of wine process and monitoring the food process microbiologically.