Inhibition of the in vitro colonic fermentation of cooked gluten by dietary fibers with individual fermentability.

Dietary fibers inhibit protein colonic fermentation, which could result from the availability, fermentability, and colloidal properties of dietary fibers, but the theory of dietary fibers acting on protein fermentation remains intricate. This paper reports the in vitro fermentation extent of steamed gluten supplemented with three dietary fibers of varying fermentability and colloidal properties. FOS inhibited gluten fermentation only at higher amounts, reducing the free amino acid (FAA) content by 36.95% (p < 0.05) and branched-chain fatty acid content by 58.17% (p < 0.05) and promoting the growth of Lactobacillus and Bifidobacterium. Cellulose even enhanced gluten fermentation at both low and high levels, resulting in a 16.33% increase in FAA content (p < 0.05) and promoting the growth of Clostridium spp. (R > 0.84, p < 0.05). Instead, alginate reduced gluten fermentation to the greatest extent, mainly by forming a dense layer that covered the gluten porosity, and sustained higher SCFA levels during fermentation, resulting in the lowest proteolytic metabolites. This study suggests that a durable fermented dietary fiber with good colloidal properties exerts better effects in delaying gluten fermentation by shielding the microbiota from degrading gluten.