Alterations in Yeast Species Composition of Uninoculated Wine Ferments by the Addition of Sulphur Dioxide

Abstract

Uninoculated wine fermentations are conducted by a consortium of wine yeast and bacteria that establish themselves either from the grape surface or from the winery environment. Of the additives that are commonly used by winemakers, sulphur dioxide (SO2) represents the main antimicrobial preservative and its use can have drastic effects on the microbial composition of the fermentation. To investigate the effect of SO2 on the resident yeast community of uninoculated ferments, Chardonnay grape juice from 2018 and 2019 was treated with a variety of SO2 concentrations ranging up to 100 mg/L and was then allowed to undergo fermentation, with the yeast community structure being assessed via high-throughput meta-barcoding (phylotyping). While the addition of SO2 was shown to select against the presence of many species of non-Saccharomyces yeasts, there was a clear and increasing selection for the species Hanseniaspora osmophila as concentrations of SO2 rose above 40 mg/L in fermentations from both vintages. Chemical analysis of the wines resulting from these treatments showed significant increases in acetate esters, and specifically the desirable aroma compound 2-phenylethyl acetate, that accompanied the increase in abundance of H. osmophila. The ability to modulate the yeast community structure of an uninoculated ferment and the resulting chemical composition of the final wine, as demonstrated in this study, represents an important tool for winemakers to begin to be able to influence the organoleptic profile of uninoculated wines.

Multi-omics framework to reveal the molecular determinants of fermentation performance in wine yeast populations

“…In addition, approximately half of SO 2 treatments did not even start the fermentation (data not shown), mostly in Lachancea or Hanseniaspora dominated samples. Different yeast species exhibit varying sensitivity to this antimicrobial, commonly used in wines, with Saccharomyces usually displaying higher tolerances [57]. We did not observe a conserved metabolite pattern associated to the fermentation conditions imposed across samples ( Supplementary Figure S5A , PERMANOVA: R 2 = 0.062, p = 0.421).…”

Effect of Aeration on Yeast Community Structure and Volatile Composition in Uninoculated Chardonnay Wines

“…Currently, the quest for novel and distinct wine flavor profiles has led winemakers to increase the use of uninoculated wine fermentations in commercial settings. While several winemaking factors can affect the composition and structure of native microbial populations [13], detailed information on how to modulate these factors to systematically influence population structure and shape wine style are only beginning to be investigated [18,21]. Particularly interesting is the use of SO 2 to positively select for H. osmophila in uninoculated ferments and consequently change the wine volatile profile [21].…”

“…SO 2 addition has been shown to impact the growth of yeast species during wine fermentation [16,[18][19][20]. Recently, the addition of SO 2 was shown to select against many non-Saccharomyces species, while increasing selection for the species Hanseniaspora osmophila in uninoculated Chardonnay ferments [21]. This positive selection was observed at certain SO 2 concentrations and it was associated with significant changes in the volatile composition of the resulting wines.…”

Enological Repercussions of Non-Saccharomyces Species 2.0

“…The use of suitable levels of SO 2 in grape must has been observed to have a positive effect in the selection of some Hanseniaspora spp. favoring the production of acetate esters, especially significant amounts of 2-phenylethyl acetate [18]. SO 2 management can be an interesting tool to modulate wild non-Saccharomyces populations for improving the aroma in uninoculated wines.…”

“…Among them, Torulaspora delbrueckii, Lachancea thermotolerans, and Metschnikowia pulcherrima [19,20], together with some apiculate yeasts [10,18,20], are key species. Torulaspora delbrueckii was the first species produced, and broadly used at an industrial level, because of the effect on wine aroma and mouthfeel [3,6].…”