Autochthonous yeasts and Lactobacillus plantarum strains: different inoculation time and wine safety and quality

Traditional vinification process includes two steps performed by microorganisms, alcoholic fermentation (AF) and malolactic fermentation (MLF). The AF is carried out by yeasts, mainly by Saccharomyces cerevisiae, that however is not the only species involved in the process. In last years, in particular, there is a special interest in the study of non-Saccharomyces yeasts as they are responsible for a considerable part of the aromatic complexity of the wine. MLF is an important phase during winemaking and the co-inoculation of lactic acid bacteria (LAB) resources with yeast starter represents a promising approach to enhance the quality and safety of wine. Lactobacillus plantarum selected strains have been receiving increasing attention as starter cultures for MLF in wine. With the aim to design of mixed culture to perform AF and MLF simultaneously in a short period of time, with complex organoleptic properties, in this work we report the evaluation of the best inoculation time of L. plantarum strains in combination with autochthonous S. cerevisiae strains and non-Saccharomyces (Hanseniaspora sp.). Microvinifications were performed using must from Apulian autochthonous grape varieties. Both, yeasts S. cerevisiae and non-Saccharomyces, were co-inoculated and L. plantarum strains were co-inoculated or sequentially inoculated during AF, when ethanol content was 2%, 4%, 6%, 8%, 10% or 12% (v/v). Ethanol formation, malic acid consumption and cell viability were monitored during the vinifications. Results showed that L. plantarum cell viability and L-malic consumption after AF was strain-dependent. L. plantarum strains showed the highest populations when it was co-inoculated with S. cerevisiae and H. uvarum. Only when the L. plantarum strains were inoculated with 0% of ethanol, all L-malic acid present in grape must (3.5 g/l) was consumed. We also reported preliminary results using the same panel of L. plantarum strains in combination with other autochthonous resources. This research was supported by the Apulian Region Project "Sviluppo di approcci microbiologici innovativi per il miglioramento della qualità di vini tipici regionali (NEWine)".