Combined effect of heat shock and must nutrition that lead stuck and sluggish wine fermentation

VARGAS A.S.; LERENA M.C.; ESTEVE-ZARZOSO B.; MAS A.; QUEROL A.; COMBINA M.

Logroño

Congreso; International Congress on Grapevine and Wine Sciences (ICGWS); 2018

Institute of Grapevine and Wine Sciences (ICVV)

Stuck and sluggish fermentations are one of the main problems affecting the wine production leading in many cases to important economic losses. Several chemical and physical factors have been associated with problematic fermentations, being exposure to extreme temperatures among them. During early fermentation stages, high metabolic activity of yeast leads to an increase in must temperature. Moreover, the nutrition of the musts with nitrogenous sources carried out during the first days of fermentation could also favour this temperature increase. The aim of this study was to identify thermal conditions leading to problematic fermentations evaluating the combined effect of heat shock and nutrition of musts. Three S. cerevisiae strains were used in this study. Fermentations were conducted at 28°C using synthetic must. The impact of heat shock at 36ºC and 40ºC was assessed increasing must temperature during 16 hours on the third day of fermentation. Additionally, two nutritional conditions: with and without diammonium phosphate additions were evaluated. Fermentation kinetic was monitored through density measurements whereas cell viability/vitality was evaluated with flow cytometry associated with PI and CFDA staining. Result showed that heat shock affected fermentation kinetics with different intensity depending on the temperature, nutritional conditions and yeast strain evaluated. None of the conditions evaluated leaded to a complete stuck fermentation, although sluggish fermentation was recorded. Thermal shock of 40°C lead to a delayed fermentation that triplicate the fermentation time respect to the control treatment. A high reduction in the percentages of viability and vitality of the yeasts was recorded after thermal shock. Yeast cells from fermentations with nutrition showed a higher sensitivity to heat shock; however, they showed a greater recovery, ending the fermentation before the treatments without nutrition.