Grant: Discovery Grants Program - Individual

Icewine is a sweet dessert wine of critical importance to the Canadian wine industry, both fiscally, with the 2004 harvest worth in excess of 90 million dollars, and commercially, since it is the flagship wine that spearheaded international trade for Canadian wines.  Producing these wines offers many challenges to wine yeast carrying out the fermentations.  The solutes in Icewine juice place wine yeast under increased hyperosmotic stress, leading to altered metabolism, fermentation difficulties and often, organoleptic faults in the wine. A high concentration of acetic acid in Icewine is one such fault that is a concern due to regulatory issues regarding its upper allowable level in wine and the association of acetic acid with wine spoilage.  Wine yeast strains display properties that are distinct from well-studied laboratory yeast strains, and these differences can impact on the organoleptic properties of wine.  However, the molecular basis of these differences is largely unknown.  The central research goal of this program is to gain a more comprehensive understanding, at the molecular level, of factors influencing wine yeast stress responses during Icewine fermentation and how these responses affect cellular redox balance, acetic acid production and Icewine quality.  We will examine such influences while yeast adapt first to the hyperosmotic stress from solutes concentrated in Icewine juice and then follow their adapted response in an oenological environment during fermentation.  Once we understand why certain metabolites are formed during this response, it should be possible to control yeast metabolism to avoid or minimize unwanted compounds such as acetic acid.  This research will provide critical information for the selection of yeast strains best suited for Icewine production and will greatly assist Canada in maintaining and expanding its global dominance in Icewine quality and production.