Project Title

Isolation and Selection of Wild Yeasts for Beer Fermentation

Academic department under which the project should be listed

Department of Molecular and Cellular Biology

Research Mentor Name

Christopher Cornelison

Abstract (300 words maximum)

Brewer’s yeast, Saccharomyces cerevisiae and Saccharomyces pastorianus, are the most widely used yeasts for beer fermentation. Hops, grain, and adjuncts are commonly known to give beer distinct flavors, but the yeast species that are pitched can promote distinct aromatic profiles. Wild yeast fermentation from natural reservoirs is at the origins of brewing and is still used today to create unique products. This study focuses on a collaboration with a local brewery to isolate and characterize wild yeasts from a variety of botanical sources for use in a special product line. Seven separate botanicals were provided by Halfway Crooks Brewery. These botanicals include American Oak Bark, Apple Blossom, Fig fruit, Mint leaves, Pomegranate fruit, Rosemary leaves, and an unidentified leaf that were sourced from local gardens in metro Atlanta and the Kennesaw State University Field Station. Yeasts from these botanical sources were isolated and analyzed in malt extract and both a rye brew and tabletop brew to determine the sensory characteristic produced by each individual strain as well as the alcohol content produced. The yeasts were successfully isolated and propagated to the desired cell count and provided to Halfway Crooks Brewery for pilot production in 30-gallon batches. The wort was segmented into individual fermenters and inoculated with only the wild yeast strains. Each fermenter was regulated at room temperature and covered to reduce light exposure. The original gravity and final gravity of each brew were taken to determine differences in alcohol content. Gas chromatography-mass spectrometry (GC-MS) was also used as an analytical method to determine the unique compounds produced by the yeast strains. These products have distinct sensory characteristics while attenuating at a favorable alcohol content.

Disciplines

Food Microbiology | Integrative Biology

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Isolation and Selection of Wild Yeasts for Beer Fermentation

Brewer’s yeast, Saccharomyces cerevisiae and Saccharomyces pastorianus, are the most widely used yeasts for beer fermentation. Hops, grain, and adjuncts are commonly known to give beer distinct flavors, but the yeast species that are pitched can promote distinct aromatic profiles. Wild yeast fermentation from natural reservoirs is at the origins of brewing and is still used today to create unique products. This study focuses on a collaboration with a local brewery to isolate and characterize wild yeasts from a variety of botanical sources for use in a special product line. Seven separate botanicals were provided by Halfway Crooks Brewery. These botanicals include American Oak Bark, Apple Blossom, Fig fruit, Mint leaves, Pomegranate fruit, Rosemary leaves, and an unidentified leaf that were sourced from local gardens in metro Atlanta and the Kennesaw State University Field Station. Yeasts from these botanical sources were isolated and analyzed in malt extract and both a rye brew and tabletop brew to determine the sensory characteristic produced by each individual strain as well as the alcohol content produced. The yeasts were successfully isolated and propagated to the desired cell count and provided to Halfway Crooks Brewery for pilot production in 30-gallon batches. The wort was segmented into individual fermenters and inoculated with only the wild yeast strains. Each fermenter was regulated at room temperature and covered to reduce light exposure. The original gravity and final gravity of each brew were taken to determine differences in alcohol content. Gas chromatography-mass spectrometry (GC-MS) was also used as an analytical method to determine the unique compounds produced by the yeast strains. These products have distinct sensory characteristics while attenuating at a favorable alcohol content.