Diet, especially with respect to consumption of dietary fibers, is well recognized as one of the most important factors shaping the colonic microbiota composition. Accordingly, many studies have been conducted to explore dietary fiber types that could predictably manipulate the colonic microbiota for improved health. However, the majority of these studies underappreciate the vastness of fiber structures in terms of their microbial utilization and omit detailed carbohydrate structural analysis. In some cases, this causes conflicting results to arise between studies using (theoretically) the same fibers. In this investigation, by performing in vitro fecal fermentation studies using bran arabinoxylans obtained from different classes of wheat, we showed that even subtle changes in the structure of a dietary fiber result in divergent microbial communities and metabolic outputs. This underscores the need for much higher structural resolution in studies investigating interactions of dietary fibers with gut microbiota, both in vitro and in vivo .

Thiamine is an essential micronutrient, but delivery of the vitamin in supplements or foods is challenging because it is unstable under heat, alkaline pH, and processing/storage conditions. Although distributed as a crystalline ingredient, thiamine chloride hydrochloride (TClHCl) likely exists in the amorphous state, specifically in supplements. Amorphous solids are generally less chemically stable than their crystalline counterparts, which is an unexplored area related to thiamine delivery. The objective of this study was to document thiamine degradation in the amorphous state. TClHCl:polymer dispersions were prepared by lyophilizing solutions containing TClHCl and amorphous polymers (pectin and PVP (poly[vinylpyrrolidone])). Samples were stored in controlled temperature (30–60 °C) and relative humidity (11%) environments for 8 weeks and monitored periodically by X-ray diffraction (to document physical state) and HPLC (to quantify degradation). Moisture sorption, glass transition temperature (T_g), intermolecular interactions, and pH were also determined. Thiamine was more labile in the amorphous state than the crystalline state and when present in lower proportions in amorphous polymer dispersions, despite increasing T_g values. Thiamine was more stable in pectin dispersions than PVP dispersions, attributed to differences in presence and extent of intermolecular interactions between TClHCl and pectin. The results of this study can be used to control thiamine degradation in food products and supplements to improve thiamine delivery and decrease rate of deficiency.

Alternative flours can reveal beneficial health effects. The aim of this study was to evaluate and compare the effects of dietary fibers (DFs) of coconut and carob flours on colonic microbiota compositions and function. Coconut flour DFs were found to be dominated by mannose‐containing polysaccharides by gas chromatography (GC)/MS and spectrophotometer, whereas glucose and uronic acid were the main monosaccharide moieties in carob flour DFs. In vitro fecal fermentation analysis revealed that coconut flour DFs result in the generation of microbial butyrate as much as inulin does, which is known to be a butyrogenic prebiotic, but at a slower rate. Supportingly, coconut flour DFs promoted butyrate‐producing bacteria including Roseburia and Coprococcus, whereas carob flour DFs stimulated Prevotella‐related OTUs. In addition, higher microbial diversity was achieved at the end of the fermentation of coconut flour DFs by the fecal microbiota. This study clearly shows that alternative flours have distinct functionalities in terms of colonic microbiota composition and function, and coconut flour could be used as an alternative flour for the development of functional food products targeting colonic health.