Evaluation of the thermal shock on the viability / vitality of Saccharomyces cerevisiae and its consequences in alcoholic fermentation.

Identifier:  TFM:283

Handle: https://hdl.handle.net/20.500.11797/TFM283

Authors:  Vargas Trinidad, Andrea Susana

Abstract:
Stuck or sluggish alcoholic fermentations are a recurring oenological problem in winemaking. The aim of this study was to contribute to the prevention of stuck and sluggish oenological fermentations through the early detection of predisposing thermal conditions, evaluating the combined effect of heat shock with other factors such as the variability of Saccharomyces strains and the nutrition of musts. Microvinifications were performed on synthetic must inoculated with two commercial strains of S. cerevisiae, PDM and ARM. Two thermal shocks (36°C and 40°C) were assessed for 16 hours on the third day of fermentation. In order to evaluate the effect of nutrition of musts, 3 hours before the shock, 200 mg/L of ammonium in the form of diammonium phosphate was added. Fermentation kinetic was monitored through the daily measuring of density whereas viability/vitality were controlled by Flow Cytometry with fluorescent dyes. Heat shocks affected the fermentative kinetics with different intensity depending on the temperature, the nutrition and the S. cerevisiae strain evaluated. No complete arrest in fermentation was observed, however sluggish fermentations were detected in some of the conditions assessed. This effect was higher in the heat shock of 40°C, PDM was more sensitive, according to the analysis of viability and vitality. Nourished fermentations culminated earlier in all cases. It is necessary to extend the study to better understand the effect of high temperatures and prevent problems in the wine industry. Keyword: wine, stuck fermentation, nitrogen and flow cytometry.