The Role of Yeasts in Traditional and Industrial Food Fermentations: Bread, Dairy and Beverages

Abstract

Yeasts are unicellular eukaryotic organisms which have been essential to food fermentation for thousands of years. This review addresses the various roles played by yeasts in the traditional and industrial manufacturing of food products such as bread, dairy products and beverages. In all these applications, Saccharomyces cerevisiae is the dominant species due to its ability to efficiently metabolize carbohydrates, its leavening properties and its flavor creating capabilities. Recent research has however highlighted the potential of non-*Saccharomyces* yeasts, including the aroma enhancing Torulaspora delbrueckii, the exopolysaccharide producing Kluyveromyces marxianus, stress-tolerant Pichia kudriavzevii and the phytase-producing Lachancea thermotolerans. Yeasts are used in bread making as leavening and flavour development agents; and some non-conventional species are being evaluated for clean label products. Yeasts are mainly used in dairy fermentations for surface-ripened cheeses and fermented milk products to aid in proteolysis, lipolysis, and in order to reduce off-flavour. In the beverage industry, there is the most variety in the use of yeast in fermentations, as in wine, beer, and spirits production, both pure and mixed culture approaches are used. Through metabolic engineering, such as with the application of the CRISPR/Cas9 genome editing system, fermentation capabilities have been optimized for strains to yield greater amounts of desirable fermentation products, as well as stress resistance and targeted flavor compound production. In addition, yeasts are now known to be promising biofactories for the production of emulsifiers, organic acids and other value-added products in the frame of circular bioeconomy. This review aims to build a summary of the existing knowledge on yeast metabolic pathways, strain selection strategies, and industrial applications of yeast-mediated food fermentation, and to envision future research avenues for yeast in food fermentation