Chapter 19: Fungi in Food Processing

Rather than focusing on fungi consumed directly, the discussion centers on fungal metabolic processes that occur invisibly yet produce profound biochemical changes in food substrates. The chapter begins with Saccharomyces cerevisiae, the primary yeast responsible for bread leavening and alcohol fermentation, where anaerobic metabolism converts sugars into ethanol and carbon dioxide through enzymatic pathways involving more than twenty distinct enzymes and cofactors. Different yeast strains produce distinct fermentation products: S. carlsbergensis generates the smooth, clean flavors characteristic of lager beers, while S. cerevisiae produces the complex esters and phenolic compounds of ales. Winemaking traditions demonstrate how fungal selection, grape cultivars, environmental conditions, and soil composition collectively influence final product characteristics, with Botrytis cinerea offering a specialized example through its role in producing dessert wines by concentrating grape sugars through selective rotting. Cheese ripening illustrates another dimension of fungal food transformation, where Penicillium species degrade casein through proteolytic enzymes or oxidize fatty acids to generate characteristic flavors and textures. Asian fermented food systems represent the most diverse fungal applications, with Aspergillus oryzae initiating koji fermentation in soy sauce production before yeast and bacterial consortia complete maturation over months or years. Tempeh demonstrates how Rhizopus oligosporus colonizes legumes to improve digestibility and nutritional bioavailability through enzymatic protein degradation. Additional examples including miso, sufu, and various regional fermented products reveal the metabolic versatility of fungal genera in substrate transformation, flavor development, and food preservation. Throughout these applications, fungi function as biotechnological agents that enhance palatability, digestibility, shelf stability, and nutritional value while maintaining safety profiles established through generations of traditional practice.