Characterization of malolactic fermentation by Lactiplantibacillus plantarum in red grape must

Malolactic fermentation (MLF) is a desirable biotransformation in red and some high-acidity white wines. This process involves the decarboxylation of l-malic acid into l-lactic acid by lactic acid bacteria (LAB). Among them, Oenococcus oeni and Lactiplantibacillus plantarum are the most common, being the last usually used as starter to perform MLF in wine. Compared with O. oeni, L. plantarum is less tolerant to wine conditions such as pH and ethanol; thus, it is preferable to inoculate it in must. The current literature has not yet addressed the impact of some parameters on the inoculation of this bacterium in grape must. Therefore, the aim of this work was to characterize the effect of the inoculum concentration, pH and ethanol tolerance, as well as the inoculation strategy, on the MLF performance of L. plantarum in grape must. We observed that a population < 108 CFU/mL could compromise MLF performance. Additionally, L. plantarum was able to survive at low pH values, such as 2.50, but in the presence of ethanol or a fermenting yeast, it could tolerate pH values in the range of 3.00–3.25. Finally, coinoculation or sequential inoculation with S. cerevisiae allows for the completion of MLF before the end of alcoholic fermentation. •The optimal inoculation rate of L. plantarum was 108 CFU/mL.•L. plantarum is suitable for improving the performance of MLF in red grape must during AF.•Both coinoculation and sequential inoculation allow MLF to occur at moderate pH values.•A low pH (