NEW INSIGHTS INTO THE EFFECT OF TORULASPORA DELBRUECKII/SACCHAROMYCES CEREVISIAE INOCULATION STRATEGY ON MALOLACTIC FERMENTATION PERFORMANCE

Abstract

Winemaking is influenced by micro-organisms, which are largely responsible for the quality of the product. In this context, Non-Saccharomyces and Saccharomyces species are of great importance not only because it influences the development of alcoholic fermentation (AF) but also on the achievement of malolactic fermentation (MLF). Among these yeasts, Torulaspora delbrueckii allows in sequential inoculation with strains of S. cerevisiae shorter MLF realizations [5] . Little information is available on the temporal effect of the presence of T. delbrueckii on (i) the evolution of AF and (ii) the MLF performance. Therefore, the objective of this study is to evaluate the effect of sequential time (2, 4 and 6 days) of T. delbrueckii/ S. cerevisiae on the achievement of MLF by two strains of Oenococcus oeni. AF and the following MLF were performed in a synthetic must supplemented with linoleic acid and b-sitosterol. The results showed that differences were observed in the duration of the AF as for example co-inoculated AF lasted less time, even compared to the control, while sequential AF were prolonged in time. Regarding the abundance of the species in co-inoculation S. cerevisiae dominated the fermentation process from the middle to the end as previously described in literature [2,3] . In sequential fermentations, T. delbrueckii represented a higher percentage at the end, 40-30% of the total population. In relation to the differences between sequential conditions it seems that during the fermentation with 4 days of T. delbruekii contact the population was higher than 2 and 6 days. As for the supplementation with lipids to the synthetic must we could observe that yeast viability increased, acetic acid decreased and AF and MLF performance improved. Regarding MLF T. delbrueckii improved the total time of the process comparing with S. cerevisiae as described in literature [1,4] . However, in the co-inoculated wines MLF had a longer duration. Regarding sequential wines, in the 4-day contact condition with T. delbruekii the MLF was shortened to two days, with the two O. oeni strains, so this seemed to be the best strategy combination.

Overall, these findings highlight the importance of considering both the inoculation strategy and the specific strains used to a better understanding of the complex interactions between these species in the fermentation process.