Evaluating non-conventional yeast for the production of wines that contain less ethanol

Summary

Objectives
This project will conduct pilot scale trials on non-conventional yeast strains or a combination of strains with the lowest ethanol yield.

Background
There is growing demand for wines with lower alcohol but still with balance, good flavour profile and other desirable characteristics. One way to achieve this is to develop yeast strains that produce less ethanol from a given amount of sugar or to develop fermentation strategies, such as sequential inoculation, to achieve the same results.

Previous laboratory trials that showed that wines produced with a sequential inoculation of a Metschnikowia pulcherrima strain followed by a Saccharomyces cerevisiae wine strain had 0.9 per cent and 1.6 per cent less alcohol in Chardonnay and Shiraz, respectively compared to wine fermented with S. cerevisiae alone. Limited work has also been undertaken with another promising non-conventional yeast.

Research approach
The plan includes laboratory studies to compare mixed cultures of the two non-conventional yeast strains as well as sequential inoculation with the conventional S. cerevisiae. The ability of the strains to grow in the presence of indigenous yeast coming from grape must (i.e. unsterilized grape juice as would be normal in wineries) will be assessed before pilot scale trials are undertaken of the most promising strains and inoculation strategies. Sensory analysis of the resultant wines is planned.

Industry benefit
This is a proof of concept project. If successful, these yeast strains and fermentation strategies will allow winemakers to produce lower alcohol wines. Although the reduction in alcohol likely to be achieved through the knowledge generated from this project is small, combining the use of these yeasts with other technologies could result in commercially advantageous lower wine alcohol concentrations.