Nutritional Aspects of Cereal Fermentation with Lactic Acid Bacteria and Yeast

Sourdough fermentation is best known and most studied for its effects on the sensory quality and shelf life of baked goods. Acidification, proteolysis, activation of enzymes and their effects on the cereal matrix as well as production of microbial metabolites all produce changes in the dough and bread matrix that also influence the nutritional quality of the products. The nutritional quality is formed through the chemical composition and structure of the fermented foods, i.e., content and bioavailability of nutrients and non-nutrients. Sourdough fermentation can change all of these, as previously reviewed by Poutanen et al. [1], Katina et al. [2], and Arora et al. [3]. Sourdough fermentation has been traditionally applied to whole grain foods, and it is a good means of making whole grain bread more palatable. Rye bread is an extreme example of this, as most of the whole-grain rye bread is made through sourdough fermentation [4]. Sourdough fermentation, also in the form of pre-treating raw materials, is again gaining interest also in mixed flour and dietary-fiber-enriched baking [5], where it also can change the properties of the dietary fiber complex. Fermentation has been studied to reduce the glycemic response of bread [6, 7], to increase the uptake of minerals [8], and to improve the digestibility [9]. Microbial metabolism during sourdough fermentation may also produce new nutritionally active compounds, such as vitamins [10], biogenic peptides [11], and potentially prebiotic exopolysaccharides [12]. Sourdough fermentation has also been recently shown to have a potentially beneficial effect on gut microbiota and subsequent gut mediated health effects [13].