Enhanced winemaking outcomes and wine style diversification through provision of fit-for-purpose yeast starter cultures
It is common practice for winemakers to choose particular yeasts in pursuit of desired wine styles. Availability of new yeasts that impart novel flavour profiles or that accentuate specific varietal characters can provide winemakers with an expanding array of options to achieve stylistic flexibility. This project aims to facilitate the development of wine styles with distinctive flavour profiles and the production of existing wine styles with lower input costs, with a particular focus on the contribution of yeast to red wine flavour. A broad approach is being taken to microbial modulation of wine flavour, including harnessing the overall genetic diversity of yeast germplasm (both within and outside the S. cerevisiae species) with the objective of establishing yeast ‘flavour profiles’ and accompanying genomic markers. Classical breeding, nutagenesis and interspecies hybridisation, guided by genomic insights into ‘what each genome brings to a wine strain’, are being applied to generate novel wine strains that modulate red wine flavour, display appropriate flocculation behaviour, produce low levels of offflavours and exhibit stable performance.
Benchmarking yeast strain impact on wine composition
Building on the previous year’s work in which the fermentation characteristics of approximately 100 genome-sequenced yeast strains were evaluated, correlations have been established between genomic datasets and, for example, the production of volatile sulfur compounds. In addition, 54 spores of wine yeasts have been trialled in fermentations. Data from these ferments is being processed and will contribute to the mapping of wine-relevant traits to genomic datasets. Knowledge gained will provide a foundation for future development of novel fit-for-purpose starter cultures.
Boosting floral aromas in red and white wines
Using a non-GMO approach, AWRI scientists have generated variants of an industry workhorse wine yeast (AWRI796) that produce enhanced levels of 2-phenylethanol (2-PE) and 2-phenylethyl acetate (2-PEA). These compounds impart ‘rose’/‘floral’ aromas in wines. Fermentation trials using one of the variants in a range of juices consistently showed large increases in the levels of 2-PE and 2-PEA in the resultant wines. Descriptive sensory analysis was generally favourable for the white varieties, with Chardonnay in particular scoring highly for desirable ‘floral’ aroma. In reds, however, the descriptors were more varied and not always positive. Further work is required to determine the potential applications of this novel yeast particularly in the context of red wine.
Novel application for interspecific hybrid wine yeast
A small number of interspecific wine yeast hybrids (two already commercialised and three currently at research status) have been evaluated for sparkling wine production in Australian and UK wineries. A collaboration with Plumpton College in the UK led to winemaking trials with three of Britain’s premier sparkling wine manufacturers: Nyetimber, Gusbourne Estate and Bolney Wine Estate. A selection of the resultant wines from the above trials was successfully showcased in a workshop at the International Cool Climate Wine Symposium held in Brighton, UK in May 2016. This has led to considerable interest in using interspecific wine yeasts for sparkling wine production.
Toni Garcia Cordente