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Type: Journal article
Title: Engineering volatile thiol release in Saccharomyces cerevisiae for improved wine aroma
Author: Swiegers, J.
Capone, D.
Pardon, K.
Elsey, G.
Sefton, M.
Francis, I.
Pretorius, I.
Citation: Yeast, 2007; 24(7):561-574
Publisher: John Wiley & Sons Ltd
Issue Date: 2007
ISSN: 0749-503X
Statement of
Jan H. Swiegers, Dimitra L. Capone, Kevin H. Pardon, Gordon M. Elsey, Mark A. Sefton, I. Leigh Francis and Isak S. Pretorius
Abstract: Volatile thiols, such as 4-mercapto-4-methylpentan-2-one (4MMP), 3-mercaptohexan-1-ol (3MH) and 3-mercaptohexyl acetate (3MHA), are among the most potent aroma compounds found in wine and can have a significant effect on wine quality and consumer preferences. At optimal concentrations in wine, these compounds impart flavours of passionfruit, grapefruit, gooseberry, blackcurrant, lychee, guava and box hedge. The enzymatic release of aromatic thiols from grape-derived, non-volatile cysteinylated precursors (Cys-4MMP and Cys-3MH) and the further modification thereof (conversion of 3MH into 3MHA) during fermentation, enhance the varietal characters of wines such as Sauvignon Blanc. Wine yeast strains have limited and varying capacities to produce aroma-enhancing thiols from their non-volatile counterparts in grape juice. Even under optimal fermentation conditions, the most efficient thiol-releasing Saccharomyces cerevisiae wine strain known realizes less than 5% of the thiol-related flavour potential of grape juice. The objective of this study was to develop a wine yeast able to unleash the untapped thiol aromas in grape juice during winemaking. To achieve this goal, the Escherichia coli tnaA gene, encoding a tryptophanase with strong cysteine-beta-lyase activity, was cloned and overexpressed in a commercial wine yeast strain under the control of the regulatory sequences of the yeast phosphoglycerate kinase I gene (PGK1). This modified strain expressing carbon-sulphur lyase activity released up to 25 times more 4MMP and 3MH in model ferments than the control host strain. Wines produced with the engineered strain displayed an intense passionfruit aroma. This yeast offers the potential to enhance the varietal aromas of wines to predetermined market specifications.
Keywords: carbon sulphur lyases
volatile thiols
wine aroma
wine yeast
sensory analysis
Description: Copyright © 2007 John Wiley & Sons, Ltd.
DOI: 10.1002/yea.1493
Appears in Collections:Agriculture, Food and Wine publications
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