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Research Project: Utilizing Non-Saccharomyces Yeast as Bioprotectants During Pre-fermentation Cold Soaking

Location: Horticultural Crops Production and Genetic Improvement Research

Project Number: 2072-21000-057-006-G
Project Type: Grant

Start Date: Sep 1, 2018
End Date: Oct 1, 2022

1. Investigate ability of commercial non-Saccharomyces yeast to suppress Hanseniaspora uvarum and acetic acid bacteria growth and volatile acidity production during pre-fermentation cold soaking. 2. Determine impact of pre-fermentation maceration conditions such as sulfur dioxide, temperature, and initial microbial populations on effectiveness of non-Saccharomyces yeast to reduce volatile acidity.

Commercial non-Saccharomyces (NS) yeast cultures will be screened for their ability to suppress the growth of H. uvarum and Acetobacter aceti during pre-fermentation cold soaking. H. uvarum and A. aceti cultures will be sourced from the Osborne laboratory culture collection. A standardized white grape juice will be used for initial screening. H. uvarum and A. aceti will be inoculated into the grape juice in either single or mixed cultures. Microbial populations will be monitored by plating and acetic acid content will be assessed after five days cold soak by enzymatic analysis. Based on results from the grape juice experiments, the three most effective non-Saccharomyces yeast cultures will be further assessed during cold soaking of Pinot noir grapes. A standardized grape juice will be used to test the impact of Sulfur dioxide (SO2) concentration, and initial population of H. uvarum and A. aceti on the effectiveness of commercial NS yeast to decrease volatile acidity. Three different SO2 concentrations and two different starting populations will be tested. A series of experiments will be conducted where combinations of SO2 and initial populations of H. uvarum and A. aceti will be prepared. Based on results from previous experiments the three most effective commercial NS yeast cultures will be used for these experiments and inoculated.