Indigenous Lactiplantibacillus plantarum and Oenococcus oeni in malolactic fermentation: effects of co-inoculation strategy and inoculation timing on fermentation kinetics and aroma profiles.

Malolactic fermentation (MLF) plays a key role in regulating acidity, microbial stability, and aroma development in red wine. Indigenous Lactiplantibacillus plantarum isolates were assessed for their potential as malolactic starter cultures, and their role in mixed fermentation with Oenococcus oeni was investigated under different inoculation strategies during Cabernet Sauvignon winemaking. Sixty isolates were screened for ethanol tolerance, β-glucosidase activity, and malolactic performance, and three strains (C10, B16, and D30) were selected for microvinification trials. Mixed MLF was associated with differences in fermentation kinetics and aroma composition in high-alcohol wine (15.44% v/v). The combination of commercial O. oeni VP41 and D30 was associated with faster malic acid degradation, whereas mixtures containing C10 or B16 coincided with higher accumulation of acetate esters and fatty acid ethyl esters associated with fruity sensory attributes. Regarding the inoculation strategies during alcoholic and malolactic fermentations, simultaneous inoculation was associated with the formation of odor-active esters and stronger fruit-related aroma perception, while sequential inoculation coincided with higher levels of diacetyl-related metabolites. The findings indicate that indigenous L. plantarum strains exhibit considerable functional diversity, and that both strain selection and inoculation strategy may contribute to differences in malolactic fermentation behavior and aroma development in high-alcohol red wines.