Anthony Heinrich, AB Biotek
Non-Saccharomyces yeast strains have been isolated from vineyards and wineries and been researched for novel properties that may have a sensory impact on wine. Following publications by The Australian Wine Research Institute in 2014 and 2016, AB Biotek secured the opportunity to manufacture and test two Metschnikowia pulcherrima strains called AWRI 1149 and AWRI 3050. After some initial difficulties and concerns about the quality and implantation of the active dry yeast into grape juice, we were successful and initiated commercial wine trials. Fermentations were conducted in 2017 and 2018 at the Hickinbotham Roseworthy Winery in Shiraz and Cabernet Sauvignon and compared to S. cerevisiae and uninoculated controls. Fermentation kinetics for M. pulcherrima wines displayed a long lag phase yet a strong yeast implantation and dominance in the early stages of fermentation. In order to ensure fermentations were completed, AWRI 1149, AWRI 3050 and the uninoculated control were sequentially inoculated at mid-point of fermentation with a commercial strain of S. cerevisiae. Wines produced with AWRI1149 and AWRI3050 showed increased concentration of colour-related compounds compared to other wines. Principle component analysis of volatile compounds showed a clear grouping for M. pulcherrima wines compared to wines made with S. cerevisiae and uninoculated controls. A trained sensory panel described wines made with the novel yeasts as having more desirable (eg. dark fruit, complex) characters and less negative (eg. vegetal, reductive) characters than the control S. cerevisiae yeast strains. Importantly, subsequent tastings of these wines 12 months after bottling have shown preservation of each of these characteristics. Although M. pulcherrima strains have been shown to decrease wine alcohol concentration, we did not observe this phenotype. Ongoing research is focusing on strategies to help M. pulcherrima exhibit this phenotype. This applied research demonstrates that AWRI 1149 and AWRI 3050 (to be named “Maurivin AWRI Obsession”) add value to wine and assist our customers in delivering improved, novel wine styles with increased aroma and palate complexity.