Not your ordinary yeast: non- Saccharomyces yeasts in wine production uncovered

Saccharomyces cerevisiae and grape juice are natural companions' and make a happy wine marriage. However, this relationship can be enriched by allowing wild' non-Saccharomyces yeast to participate in a sequential manner in the early phases of grape must fermentation. However, such a triangular relationship is complex and can only be taken to the next level' if there are no spoilage yeast present and if the wine yeast' - S.cerevisiae - is able to exert its dominance in time to successfully complete the alcoholic fermentation. Winemakers apply various matchmaking' strategies (e.g. cellar hygiene, pH, SO2, temperature and nutrient management) to keep spoilers' (e.g. Dekkera bruxellensis) at bay, and allow compatible' wild yeast (e.g. Torulaspora delbrueckii, Pichia kluyveri, Lachancea thermotolerans and Candida/Metschnikowiapulcherrima) to harmonize with potent S.cerevisiae wine yeast and bring the best out in wine. Mismatching can lead to a two is company, three is a crowd' scenario. More than 40 of the 1500 known yeast species have been isolated from grape must. In this article, we review the specific flavour-active characteristics of those non-Saccharomyces species that might play a positive role in both spontaneous and inoculated wine ferments. We seek to present single-species' and multi-species' ferments in a new light and a new context, and we raise important questions about the direction of mixed-fermentation research to address market trends regarding so-called natural' wines. This review also highlights that, despite the fact that most frontier research and technological developments are often focussed primarily on S.cerevisiae, non-Saccharomyces research can benefit from the techniques and knowledge developed by research on the former.