Redox reactions in food fermentations

Food fermentations are typically performed without actively supplying air. Except for possible surface microorganisms, oxygen will only be transiently available and the redox reactions during the fermentation need to be in balance. Production of ATP from fermentation of carbohydrates typically involves oxidative steps in the early part of the pathways whereas a multitude of different reactions are used as compensating reductions. Much of the diversity seen between food fermentations arise from the different routes and the different electron acceptors used by microorganisms to counterbalance the initial oxidative steps. This review gives a short overview of the routes employed by microorganisms in food fermentations to find ultimate electron acceptors allowing them to balance their fermentative metabolism. The diversity of acceptors used leads to diversity of metabolic end products and this contributes to the diversity in flavor, color, texture, and shelf life. The review concludes that these reactions are still only incompletely understood and that they represent an interesting area for fundamental research and also represent a fertile field for product development through a more conscious use of the redox properties of strains used to compose food cultures.