Identification and characterisation of Saccharomyces cerevisiae strains isolated from spontaneous fermentation of organic Pinot noir wines : A thesis submitted in partial fulfilment of the requirements for the Degree of Master of Science at Lincoln University

Abstract

This study characterised Saccharomyces cerevisiae populations from the spontaneous fermentation of organic Pinot noir wines produce in Waipara, Aotearoa New Zealand, using a DNA-based Interdelta typing method to evaluate their strain diversity and population dynamics. One hundred and sixty-one S. cerevisiae isolates from key fermentation stages were differentiated by interdelta typing into 106 different genotypes (profiles), of which 24 were observed more than once. One interdelta genotype was observed among each of the fermentation stages studied. The S. cerevisiae population showed a high level of strain diversity with evident dominant groupings of strains during and between fermentation stages. Saccharomyces cerevisiae strain diversity increased towards the end of fermentation accompanied with late-stage dominance by the species. Spontaneous fermentation of organically produced wine may harbour a genetically diverse population of S. cerevisiae strains but appears to be dominated by few genotypes. The influence of each genotype on the organoleptic properties of the eventual product is unknown at this point. However, the use of interdelta typing to identify strains of special relevance with commercial potential is supported.