EVALUATION OF INDIGENOUS CANADIAN YEAST STRAINS AS WINE STARTER CULTURES ON PILOT SCALE FERMENTATIONS

Abstract

The interactions between geographical and biotic factors, along with the winemaking process, influence the composition and sensorial characteristics of wine¹. In addition to the primary end products of alcoholic fermentation, many secondary metabolites contribute to wine flavor and aroma and their production depends predominantly on the yeast strain carrying out the fermentation. Commercially available strains of S. cerevisiae help improve the reproducibility and predictability of wine quality. However, most commercial wine strains available on the market have been isolated from Europe, are genetically similar, and may not be the ideal strain to reflect the terroir of Canadian vineyards². Instead, indigenous S. cerevisiae strains may enhance the typical sensory properties and characteristic profile of the wine region³. The Okanagan Valley is the major wine-producing region in British Columbia, Canada. The Measday lab has isolated S. cerevisiae indigenous strains from Okanagan Valley vineyards that are genetically distinct from commercial strains⁴. After evaluating the oenological characteristics of six indigenous strains isolated from Okanagan Crush Pad (OCP) winery in laboratory-scale fermentations, two were selected for pilot-scale winery fermentations to assess their potential as wine starter cultures. Fermentations with OCP088 and OCP125 yeast strains were carried out in triplicate 250L stainless steel barrels at OCP winery. Vin Gris (VG, Pinot Noir) and Pinot Gris (PG) varietals were chosen, the grapes were pressed, and the juice was settled to remove skins before inoculation. Major metabolites (organic acids, sugars, and ethanol) were quantified using HPLC-RID, sugar in both wines was mainly fructose, ranging between 16 g/L and 20 g/L, ABV of the finished product ranged between 10.8 and 11.3 %. Volatile compounds (terpenes, esters, ketones, and higher alcohols) were identified using SPME-GC/MS We identified the following number of volatile compounds in each fermentation: OCP125 PG (56), OCP088 PG (52), OCP125 VG (45), OCP088 VG (44). The majority of volatile compounds were esters, which are known for their contribution to wine quality. OCP 125 tended to produce more terpenes than OCP 088. Some of these compounds are responsible for honey and grapefruit-like aromas, which are atypical of these varietals, adding to the complexity of the final product.