In Vitro  Batch Fecal Fermentation Comparison of Gas and Short‐Chain Fatty Acid Production Using “Slowly Fermentable” Dietary Fibers

Abstract: Sustained colonic fermentation supplies beneficial fermentative by‐products to the distal colon, which is particularly prone to intestinal ailments. Blunted/delayed initial fermentation may also lead to less bloating. Previously, we reported that starch‐entrapped alginate‐based microspheres act as a slowly fermenting dietary fiber. This material was used in the present study to provide a benchmark to compare to other “slowly fermentable” fibers. Dietary fibers with previous reports of slow fermentation, namely, long‐chain inulin, psyllium, alkali‐soluble corn bran arabinoxylan, and long‐chain β‐glucan, as well as starch‐entrapped microspheres were subjected to in vitro upper gastrointestinal digestion and human fecal fermentation and measured over 48 h for pH, gas, and short‐chain fatty acids (SCFA). The resistant fraction of cooked and cooled potato starch was used as another form of fermentable starch and fructooligosaccharides (FOS) served as a fast fermenting control. Corn bran arabinoxylan and long‐chain β‐glucan initially appeared slower fermenting with comparatively low gas and SCFA production, but later fermented rapidly with little remaining in the final half of the fermentation period. Long‐chain inulin and psyllium had slow and moderate, but incomplete, fermentation. The resistant fraction of cooked and cooled potato starch fermented rapidly and appeared similar to FOS. In conclusion, compared to the benchmark slowly fermentable starch‐entrapped microspheres, a number of the purported slowly fermentable fibers fermented fairly rapidly overall and, of this group, only the starch‐entrapped microspheres appreciably fermented in the second half of the fermentation period. Practical Application: Consumption of dietary fibers, particularly commercial prebiotics, leads to uncomfortable feelings of bloating and flatulence due to their rapid degradation in our large intestine. This article employs claimed potential slowly fermenting fibers and compares their fermentation rates with a benchmark slow fermenting fiber that we fabricated in an in vitro simulation of the human digestive system. Results show a variety of fermentation profiles only some of which have slow and extended rate of fermentation.