EVALUATION OF INDIGENOUS SACCHAROMYCES CEREVISIAE ISOLATES FOR THEIR POTENTIAL USE AS FERMENTATION STARTERS IN ASSYRTIKO WINE

Abstract

Assyrtiko is a rare ancient grape variety that constitutes one of the most popular in Greece. The objective of the current research was to evaluate indigenous Saccharomyces cerevisiae isolates as fermentation starters and also test the possible strain impact on volatile profile of Assyrtiko wine. 163 S. cerevisiae isolates, which were previously selected from spontaneous alcoholic fermentation, were identified at strain level by interdelta-PCR genomic fingerprinting. Yeasts strains were examined for their fermen-tative capacity in laboratory scale fermentation on pasteurized Assyrtiko grape must. Daily glucose and fructose consumption was monitored and at the final point free sorting task was conducted to categorize the samples according to their organoleptic profile. The most performant strains were selected and sub-sequently subjected in a second laboratory scale fermentation. Oenological properties such as, titratable acidity, glucose/fructose consumption, total acidity, volatile acidity, pH, L-malic acid, yeast assimilable nitrogen, free and total SO₂ as well as sensory characteristics were determined. Finally, two wines with different aromatic profiles were subjected in Gas Chromatography- Olfactometry- Mass Spectrometry (GC-O MS) analysis. The molecular typing revealed the presence of 20 different S. cerevisiae strains from which 65% indicated high fermentative capacity. Hierarchical Cluster Analysis (HCA) based on sensory evaluation results clearly discriminated the produced wines and led to the selection of 4 strains. After the second pilot fermentation all selected strains resulted in dry wines with desirable technological and organoleptic characteristics. Additionally, statistically significant differences were noticed regar-ding the perception of tropical fruits and acidity while according to the results of GC-O MS analysis both samples revealed similar aromatic profiles. To the best of our knowledge, this is the first assay that ex-plores the yeast strain effect on the aromatic profile of Assyrtiko variety by means of GC-O MS analysis.

Acknowledgements: This research has been co-financed by the European Union and Greek national funds through the Operational Program Competitiveness, Entrepreneurship and Innovation, under the call ” Greece – Israel Call for Proposals for Joint R&D Projects 2019″(project code: T10ΔΙΣ-00060).