The aim of the study was to investigate the interaction between commercial S. cerevisiae starter cultures, non-Saccharomyces yeasts and lactic acid bacteria (LAB).
Experimental layout:
- Five Saccharomyces and 37 non-Saccharomyces yeast strains (seven different species) were evaluated in synthetic grape juice to determine yeast and LAB compatibility.
- Selected yeast and LAB were also evaluated in small-scale (20 l) Chardonnay, Merlot and Shiraz wine production trials.
- Standard chemical parameters and volatile compounds were determined and the wines were also subjected to a sensory evaluation.
Main results:
- Most of the non-Saccharomyces yeasts evaluated were compatible with LAB and did not inhibit LAB growth, but there were exceptions.
- LAB inhibition was mainly due to competition for nutrients or production of toxic metabolites by the yeast strains.
- Wines produced with non-Saccharomyces yeasts contained lower alcohol levels and completed MLF in shorter periods than wines produced with S. cerevisiae strains only.
- Wines that underwent simultaneous MLF completed faster than wines that underwent sequential MLF.
- Non-Saccharomyces yeasts in combination with different S. cerevisiae strains and MLF strategies (no MLF, simultaneous or sequential MLF) produced wines with significantly different chemical composition and sensory properties. Differences in volatile composition did not always translate to perceivable sensory differences.
- The use of non-Saccharomyces yeasts to improve wine flavour and quality is affected by S. cerevisiae yeast strain and also grape cultivar.
- Wines that underwent sequential MLF had more flavour than wines that underwent simultaneous MLF, but this trend varied between cultivars and was affected by yeast strain used.
- Shiraz wines produced with non-Saccharomyces yeasts in combination with S. cerevisiae and LAB had more colour than wines produced S. cerevisiae only.
Significance of the study:
Commercial and non-commercial non-Saccharomyces yeast strains had a beneficial impact on the completion of MLF, which include induced MLF, using commercial cultures, and spontaneous MLF. The use of the suitable non-Saccharomyces yeast strains may help to reduce alcohol concentrations, while enhancing wine complexity, which could be used as a unique marketing strategy. The use of non-Saccharomyces yeasts and different MLF strategies gives winemakers the tools to produce wines of differing styles and flavour profiles. The benefits of finding a suitable non-Saccharomyces, Saccharomyces yeast and LAB combinations are faster completion of MLF, enhanced wine complexity and even improved colour.
Researcher: Dr Heinrich du Plessis
Image: Shutterstock
