Influence of yeast strains on managing wine acidity using Lactobacillus plantarum

Lactobacillus plantarum has been used for deacidifying wines through malolactic fermentation (MLF), and more recently for acidifying them. The species Oenococcus oeni is mainly responsible for MLF in wines at a pH below 3.5. However, the Lactobacillus and Pediococcus species can carry out this reaction in wines at a higher pH. MLF generally begins once yeasts have completed alcoholic fermentation, but nowadays some winemakers prefer carrying out MLF simultaneously to alcoholic fermentation. The advantages of this strategy are shorter times in which to complete wine vinification and better wine color stabilization. Lactobacillus plantarum is preferred to O. oeni for performing early MLF because it catabolizes hexoses homofermentatively, which prevents acetic acid from increasing. In recent years, wine composition has changed as a result of climate change. High temperatures during the maturation time of grapes give rise to musts with low contents of organic acids, a high pH and high sugar contents, which give wines with low acidity, a high ethanol content and a faded color. Although several physical or chemical procedures can increase acidity, it can also be achieved by using microorganisms capable of transforming sugars into acids (biological acidification); e.g. lactic acid bacteria (LAB). The advantages of this procedure are increased wine acidity and reduced ethanol content. When early MLF or biological acidification is desired, yeasts and bacteria must develop together in grape must. In this work, we studied the consequences of the interactions of different combinations of two strains of L. plantarum and six commercial strains of Saccharomyces cerevisiae during white grape must fermentation. We demonstrated that managing wine acidity is possible by co-inoculating L. plantarum and S. cerevisiae. MLF was performed with any LAB/yeast combination, but the degree of biological acidification depended on the combination. LAB growth was more negatively affected by yeast than vice versa. The best combination to manage wine acidity was L. plantarum E4608 and Uvaferm VRB*.