The effect of linoleic acid on the Sauvignon blanc fermentation by different wine yeast strains

Abstract

The level of linoleic acid in the Sauvignon blanc (SB) grape juice affects the development of different aroma compounds during fermentation by Saccharomyces cerevisiae EC1118, including key varietal thiols such as 3-mercaptohexanol (3MH) and 3-mercaptohexyl acetate (3MHA). However, it is still unknown if linoleic acid would affect in a similar way other commonly used S. cerevisiae wine strains. Here we investigated the effect of grape juice linoleic acid on the development of aroma compounds and other metabolites of SB wines using different wine yeast strains: EC1118, AWRI796 and VIN13. Linoleic acid clearly affected the levels of acetylated aroma compounds, several amino acids, and antioxidant molecules, independent of yeast strain, but the production of 3MH was affected by linoleic acid in a strain-specific manner. Moreover, the supplementation of deuterium-labelled 3MH also affected the production of varietal thiols in a strain-specific way. Linoleic acid reduced the acetylation process probably by inhibiting an acetyltransferase, an effect that was independent of the yeast strain. However, regulation of the 3MH biosynthesis is strain-specific, which suggests a mindful consideration not only towards the wine yeast but also to the linoleic acid concentration in the grape juice in order to obtain the desired wine aroma characteristics.

Impact of Nutrient Availability on the Fermentation and Production of Aroma Compounds Under Sequential Inoculation With M. pulcherrima and S. cerevisiae

“…The production of 3MHA was also variable depending on nutrient availability under both inoculation strategies. A positive impact of nitrogen, a negative effect of lipids -in agreement with the negative effect of linoleic acids on 3MHA reported by Casu et al (2016) -and an interaction between nitrogen and lipids were observed. The profile of 3MHA production depending on nutrient availability was close to that reported for acetate esters (Rollero et al, 2014).…”

Effect of free fatty acids and lipolysis on Sauvignon Blanc fermentation

“…Fujii et al () reported that the acquisition of UFAs by S. cerevisiae represses acetyl transferases 1 and 2 ( ATF1 and ATF2 ), which regulate the acetylation processes within the yeast cell resulting in the reduction of 3MHA concentration. Our current results and previous studies with linoleic acid supplementation also showed similar trends of 3MHA reduction when UFAs were supplemented to the grape juice (Pinu et al , Casu et al ). We did not observe, however, any significant increase in the 3MH concentration in the ferments from juice supplemented with FFAs.…”

“…The same trend was not observed in the experiment with linoleic acid supplementation. This finding indicates that lipase supplementation may not be directly affecting the production and secretion of 3MH and 3MHA by S. cerevisiae , but may be regulating their ratio in the extracellular medium through de‐esterification of 3MHA into 3MH via enzymatic activity, while linoleic acid may have affected the production of these volatile thiols intracellularly by downregulating the acetylation processes in yeast cells as previous reported (Fujii et al , Pinu et al , Casu et al ).…”

“…We have demonstrated that trace amounts of a polyunsaturated fatty acid commonly found in Sauvignon Blanc grape juice and linoleic acid can significantly influence yeast metabolism and the production of aroma compounds during winemaking, mainly through the reduction of 3MHA and other acetylated esters (Pinu et al , Casu et al ). Unsaturated fatty acids (UFAs) are essential nutrients for yeast growth under anaerobic conditions.…”

“…Therefore, it is not surprising that linoleic acid affects yeast metabolism during winemaking. We did not expect, however, that a trace amount of this polyunsaturated fatty acid in the grape juice could have a marked effect on the development of aroma compounds in the resulting wines (Pinu et al , Casu et al ).…”