Saccharomyces cerevisiae Diversity in Arbutus unedo L. Fermentations in Association with the Volatile and Sensory Similarities of the Distillates.

The fermentation of Arbutus unedo L. fruit is traditionally carried out in the production of spirits. The present study followed the spontaneous fermentation of A. unedo fruit harvested in October and December 2019 by two producers from the central region of Portugal. The microbiota was studied, and although a great diversity of indigenous yeasts was found, S. cerevisiae isolates could still be grouped into eight clusters, and a good separation between producers was achieved. Based on the results of a multivariate analysis of the physical-chemical and volatile composition of the distillates, a distinction between the distillates from the two producers was determined. Moreover, these findings are corroborated by the similarities in flavor that were found. Along with the variability found in the distillates, S. cerevisiae isolates could be clustered and associated with each producer. On the other hand, the differentiation of the harvesting period was not so clear. The characterization of the indigenous yeasts associated with the fermentation process of Arbutus unedo L. fruit can serve as an important contribution to the preservation of the specific characteristics of its distillates.

Influence of red wine fermentation oenological additives on inoculated strain implantation.

Pure selected cultures of Saccharomyces cerevisiae starters are regularly used in the wine industry. A survey of S. cerevisiae populations during red wine fermentations was performed in order to evaluate the influence of oenological additives on the implantation of the inoculated strain. Pilot scale fermentations (500 L) were conducted with active dry yeast (ADY) and other commercial oenological additives, namely two commercial fermentation activators and two commercial tannins. Six microsatellite markers were used to type S. cerevisiae strains. The methodology proved to be very discriminating as a great diversity of wild strains (48 genotypes) was detected. Statistical analysis confirmed a high detection of the inoculated commercial strain, and for half the samples an effective implantation of ADY (over 80 %) was achieved. At late fermentation time, ADY strain implantation in fermentations conducted with commercial additives was lower than in the control. These results question the efficacy of ADY addition in the presence of other additives, indicating that further studies are needed to improve knowledge on oenological additives' use.