Use of lactic acid bacteria for must acidification and bioprotection

Abstract

Climate change is altering grape composition, producing musts with more sugar and fewer organic acids. The resulting wines generally have higher alcohol levels and pH, lower total acidity, and increased susceptibility to spoilage microorganisms, while sulphur dioxide becomes less effective. This study evaluated lactic acid bacteria as tools for biological acidification and bioprotection. Moscatel must was inoculated with two Lactiplantibacillus plantarum strains: commercial ML Prime and the selected strain PN181. After pre-adaptation in OPM medium, bacteria were inoculated at 5 × 10⁶ cells/mL, followed 48 h later by Aroma White yeast. Lactic acid, pH and microbial populations were monitored throughout fermentation; a non-inoculated control was also produced. The pH decreased by 0.35 and 0.36 units with ML Prime and PN181, respectively, compared with 0.21 in the control. After 14 days, lactic acid concentrations reached 6.96 g/L with ML Prime and 6.81 g/L with PN181, whereas the control contained 3.46 g/L. PN181 also showed lower microbial species richness during fermentation than the commercial strain and the control. Lactic acid bacteria therefore represent an effective strategy for increasing wine acidity through lactic acid production and pH reduction while improving microbiological stability.