Together is better: experience of simultaneous fermentation of yeast and bacteria as a possible strategy to prevent stuck fermentation in difficult wines

In the field of winemaking, malolactic fermentation is a key aspect in obtaining high quality wines. Unfortunately, in some oenological contexts effective evolution does not take place because of the occurrence of certain limiting factors for malolactic bacteria in wine. Simultaneous alcoholic and malolactic fermentation in grape must is a promising alternative that promotes the survival of bacteria, due to the absence of certain limiting factors such as ethanol or other toxic substances produced by yeasts in the native grape must. The risk of wine depreciation due to the spoilage activity of malolactic bacteria can be reduced by using selected strains of Oenococcus oeni, with proven behaviour in terms of malolactic fermentation occurring in the presence of sugars. In this work we compared the activity of a strain of Oenococcus oeni in malolactic fermentation of a Chardonnay grape must, using different winemaking protocols characterised by sequential or simultaneous inoculums of microbial starters. The results are discussed both in terms of fermentative behaviour and the quality of the wines obtained, with careful analysis of the main chemical parameters of the wines and of 47 different volatile compounds, giving an exhaustive overview of the opportunities and the risks related to different wine fermentation strategie