Abstract
Sourdough fermentation by lactic acid bacteria is commonly used in bread baking, affecting several attributes of the final product. We analyzed whole-grain wheat and rye breads and doughs prepared with baker’s yeast or a sourdough starter including Candida milleri, Lactobacillus brevis and Lactobacillus plantarum using non-targeted metabolic profiling utilizing LC–QTOF–MS. The aim was to determine the fermentation-induced changes in metabolites potentially contributing to the health-promoting properties of whole-grain wheat and rye. Overall, we identified 118 compounds with significantly increased levels in sourdough, including branched-chain amino acids (BCAAs) and their metabolites, small peptides with high proportion of BCAAs, microbial metabolites of phenolic acids and several other potentially bioactive compounds. We also identified 69 compounds with significantly decreased levels, including phenolic acid precursors, nucleosides, and nucleobases. Intensive sourdough fermentation had a higher impact on the metabolite profile of whole-grain rye compared to milder whole-grain wheat sourdough fermentation. We hypothesize that the increased amount of BCAAs and potentially bioactive small peptides may contribute to the insulin response of rye bread, and in more general, the overall protective effect against T2DM and CVD.
Highlights
Increasing evidence is supporting the protective effect of whole-grain cereal consumption against several noncommunicable diseases, such as type 2 diabetes mellitus, cardiovascular disease and colorectal cancer, as well as overall mortality[1,2,3]
The principal component analysis indicated that the most substantial difference in the metabolic profiles of the analyzed samples was between the flours and all the other samples
Many of the observed changes in the metabolite levels were specific to rye sourdough; overall, sourdough fermentation of whole-grain wheat produced considerably less significantly changed metabolites and a less separated metabolic profile from yeast-fermented wheat dough and bread in the Principal component analysis (PCA)
Summary
Increasing evidence is supporting the protective effect of whole-grain cereal consumption against several noncommunicable diseases, such as type 2 diabetes mellitus, cardiovascular disease and colorectal cancer, as well as overall mortality[1,2,3]. This has been attributed to cereal dietary fiber and the array of phytochemicals within the fiber matrix[4,5], both of which interact with gastrointestinal microbiota and undergo transformations, possibly mediating physiological changes[6]. The proportion of identified compounds was maximized by combining the use of a standard library, database searches, in silico generated mass spectra, and MS/MS fragment motifs associated with certain molecular moieties
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