Evaluating the effect of using non-Saccharomyces on Oenococcus oeni and wine malolactic fermentation

Interest in using non-Saccharomyces yeasts in winemaking has increased in recent years due to their ability to improve wine quality. However, little information has been published regarding the possible effect on malolactic fermentation (MLF), carried out mostly by Oenococcus oeni. The aim of this paper is therefore to evaluate the effect of the most representative non-Saccharomyces species on O. oeni and wine MLF. Different strains of Torulaspora delbrueckii, Metschnikowia pulcherrima, Hanseniaspora uvarum, Hanseniaspora vineae and Starmerella bacillaris (syn. Candida zemplinina) were used in sequential alcoholic fermentation with Saccharomyces cerevisiae. The resulting wines were inoculated with four O. oeni strains. The action of non-Saccharomyces affected the final wine composition and the later role of O. oeni. Some of its strains could not perform MLF in H. uvarum wine due to high SO₂ concentrations. In some cases, MLF was inhibited in wines inoculated with S. bacillaris. All the H. uvarum and H. vineae strains notably increased acetic acid concentrations, thus threatening wine quality. The best conditions for MLF were provided by some T. delbruecckii and M. pulcherrima strains, which showed increased concentrations of mannoproteins - compounds described as MLF activators -, no production of SO₂, and low consumption of L-malic acid. In conclusion, non-Saccharomyces yeasts have diverse effects on O. oeni and MLF depending on the species, with T. delbrueckii and M. pulcherrima being those that showed the best compatibility with MLF development.