Effect of transient thermal shocks on alcoholic fermentation performance

Abstract

Stuck and sluggish fermentations are among the main problems in winemaking industry leading to important economic losses. Several factors have been described as causes of stuck and sluggish fermentations, being exposure to extreme temperatures barely studied. The objective of this study was to identify thermal conditions leading to stuck and sluggish fermentations, focusing on the impact of an abrupt and transient decrease/increase of temperature on fermentation performance and yeast viability/vitality. Different strains of Saccharomyces cerevisiae, SBB11, T73, and PDM were evaluated in synthetic grape must fermentations. Cold shocks (9 °C and 1.5 °C for 16 h) carried out on different days during the fermentation process were unable to alter fermentation performance. Conversely, shock temperatures higher than 32 °C, applied in early stages of the process, lead to sluggish fermentation showing a delay directly related to the temperature increase. Fermentation delay was associated with a decrease in cell vitality. The impact of the heat shock on fermentation performance was different depending on the strain evaluated and nitrogen supplementation (with or without diammonium phosphate addition). None of the conditions evaluated produced a stuck fermentation and importantly, in all cases must nutrition improved fermentation performance after a heat shock.

Identification of Molecular Markers for Early Detection of Sluggish Fermentation Associated with Heat Shock during Alcoholic Fermentation

“…In a previous study, our group found that after a heat shock during the third day of AF, two S. cerevisiae strains showed contrasting behavior after sudden temperature increases. S. cerevisiae strain SBB11 was found to be the most sensitive to heat shock, with sluggish fermentation at 36 and 40 • C. On the other hand, S. cerevisiae PDM was the most thermotolerant strain, with sluggish fermentation only observed after heat shock at 40 • C, with an insensitive response to 36 • C heat shock [7]. Samples from both strains obtained 40 min after heat shock onset were subjected to RNA-seq analysis.…”

“…This study identified two strains with contrasting heat shock behavior. While SBB11 was found to be quite sensitive, PDM was highly thermotolerant [7].…”

“…Fermentations were conducted with the thermosensitive strain S. cerevisiae SBB11 and the thermotolerant strain PDM [7]. Heat shocks were applied at 36 and 40 • C on day 3 of AF.…”

“…Samples were centrifuged, and pellets were immediately frozen in liquid nitrogen and Experimental design. Two S. cerevisiae strains previously selected [7] with contrasting behavior upon heat shock were evaluated by transcriptomic response after heat shock [10] (A). Candidate gene selection took place after RNA-seq data analysis from samples collected 40 min after heat shock.…”

“…Three S. cerevisiae strains (SBB11, PDM and T73) were subjected to heat shock during AF. The heat shock effect on fermentation kinetics differed according to the yeast strain [7]. Post heat shock outcomes depended on yeast thermotolerance and the applied temperature.…”