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Research Project: Use of Non-Saccharomyces Yeasts to Ferment High Sugar Chardonnay Grape Musts from the Pacific Northwest

Location: Horticultural Crops Production and Genetic Improvement Research

Project Number: 2072-21000-057-025-G
Project Type: Grant

Start Date: Sep 1, 2021
End Date: Oct 31, 2023

Objective:
1. Evaluate the impacts of sugar concentration on fermentation of Chardonnay grape musts applying sequential inoculations of non-Saccharomyces with Saccharomyces yeasts. 2. Investigate specific mechanisms responsible for ‘mouthfeel’ effects by non-Saccharomyces yeasts, focusing on synthesis of different polysaccharides (e.g., beta-glucans) and/or biomass formation in wines.

Approach:
Objective 1: Chardonnay grapes will be obtained from a regional commercial vineyard and crushed/destemmed using standard methods. After incorporation of 30 mg/L total SO2 using K2S2O5, equal ratios of glucose and fructose will be added to yield different initial concentrations of fermentable sugar (24°, 27°, or 30° Brix). Fermentations will be conducted using 300 L stainless steel, jacketed tanks equipped with temperature control. Starter cultures of Mt. pulcherrima and My. guilliermondii will be prepared and inoculated into duplicate, if not in triplicate, tanks musts to yield populations of 105 to 106 CFU/mL. After two days, Saccharomyces cerevisiae QA 23 (Lallemand Inc., Montréal, Quebec, Canada) will be rehydrated according to manufacturer’s instructions and inoculated at 106 CFU/mL. Fermentation will be conducted at 20°C. During fermentation, yeast viabilities will be determined using lysine media (non-Saccharomyces) and wort (all yeasts) agars while sugar utilization measured by methods previously described. Wines will be bottled (>24 bottles per treatment) in preparation of chemical (pH, titratable and volatile acidities, residual sugar, and ethanol) and sensory analyses, the latter working with the Washington State University laboratory. If sensory differences exist, descriptive analysis using a trained sensory panel will be conducted. Statistical analyses of all data will include ANOVA as well as mean separations using Fisher’s least-significant-difference. Objective 2: The experimental design outlined in Objective 1 will be replicated but under smaller scale (5 L ferments). During fermentation, samples will be analyzed for presence of glucans and biomass to examine potential correlations with mouthfeel or other sensory parameters identified as part of sensory analyses performed on wines made during Objective 1.