Yeast Communities Influence Regional Character in New Zealand Pinot Noir

Abstract

Recent studies have suggested that yeast and other micro organisms may contribute to a wine's regional distinctiveness. This study represents the first attempt to experimentally test how yeast communities, consisting of multiple isolates and species, contribute to regional wine attributes in a controlled environment. It sought to explore the following questions using New Zealand Pinot Noir as a medium: • Are yeast communities present in the early stages of uninoculated Pinot Noir fermentations regionally distinct in New Zealand? • Do these yeast communities - including non-Saccharomyces species - modulate wine aroma and/or fermentation kinetics in a regionally distinct manner? • Is there a community effect on fermentation kinetics and/or wine aroma? New methodologies for preparing a mixed species inoculum from regional yeast communities in a repeatable manner were optimised. Synthetic yeast communities comprised of natural isolates were successfully collated for 17 vineyard sites across Martinborough, Marlborough and Central Otago in New Zealand. This allowed community contribution to regional character to be explored in a controlled setting for the first time. The species present during the early stages of uninoculated New Zealand Pinot Noir fermentations were identified; however, we were unable to reject the null hypothesis of no difference in species composition between the three geographic regions since regional differences were not found in the types of species present during the early stages of fermentation. Wines were produced using these yeast communities and 28 yeast-derived aroma compounds were measured via Headspace Solid-Phase Dynamic Extraction Coupled with Gas Chromatography-Mass Spectrometry. Yeast community composition was found to have a significant impact on wine sensory attributes and fermentation kinetic variables. The region the communities were from was also found to have a significant impact on wine sensory attributes; however, the impact on fermentation kinetics was mixed. These results allowed us to reject the two remaining null hypotheses and accept the alternative hypotheses that yeast communities modulate wine aroma in a regionally distinct manner; and that the composition of these communities also modulates wine aroma and fermentation kinetics. This suggests that there is a microbial component to regional character for New Zealand Pinot Noir.