Carbohydrates blended with polydextrose lower gas production and short-chain fatty acid production in an in vitro system.

Maximizing health benefits of prebiotics, while limiting negative side effects, is of importance to the food industry. This study examined several oligosaccharides and their blends in an in vitro fermentation model. Substrates included medium- and long-chain fructooligosaccharides (FOS), oligofructose-enriched inulin, galactooligosaccharide, polydextrose (POL), and 50:50 substrate blends. Substrates and blends were fermented in vitro using human fecal inoculum, and fermentation characteristics were quantified at 0, 4, 8, and 12 hours. We hypothesized that mixtures of short- and long-chain oligosaccharides would generate less gas than do short-chain oligosaccharides and modulate gut microflora to a greater extent than do long-chain oligosaccharides. Carbohydrates blended with POL had decreased (P < .01) total gas volume and H(2) produced after 4, 8, and 12 hours of fermentation compared with individual carbohydrates. Mixing of 2 oligofructose-enriched inulin products led to less (P < .05) gas produced and a slower (P < .05) rate of production. When mixed with POL, all carbohydrates tested in the present study produced less total short-chain fatty acids (P < .04) and butyrate (P < .0001) after 12 hours of in vitro fermentation, compared with individual carbohydrates. The bifidogenic effect of medium-chain FOS and oligofructose-enriched inulin after 12 hours of in vitro fermentation was lower (P < .05) when mixed with POL. Mixing the pure carbohydrates with galactooligosaccharide increased (P < .05) bifidobacteria counts measured after 12 hours of in vitro fermentation, except when mixed with medium-chain FOS. In general, when mixed with POL, all carbohydrates had lower gas production, gas production rates, butyrate and total short-chain fatty acid production, and bifidobacteria counts than when fermented alone for 12 hours.

Dietary fibers affect viscosity of solutions and simulated human gastric and small intestinal digesta.

Two experiments were conducted to determine the viscosities of both soluble and insoluble dietary fibers. In Expt. 1, corn bran, defatted rice bran, guar gum, gum xanthan, oat bran, psyllium, soy hulls, stabilized rice bran, wheat bran, wood cellulose, and 2 methylcellulose controls (Ticacel 42, Ticacel 43) were hydrated in water overnight at 0.5, 1, 1.5, or 2% concentrations. In Expt. 2, guar gum, oat bran, psyllium, rice bran, wheat bran, and wood cellulose were subjected to a 2-stage in vitro gastric and small intestinal digestion simulation model. Viscosity was measured every 2 and 3 h during gastric and small intestinal simulation, respectively. Viscosities in both experiments were measured at multiple shear rates. Viscosities of all fiber solutions were concentration- and shear rate-dependent. Rice brans, soy hulls, and wood cellulose had the lowest viscosities, whereas guar gum, psyllium, and xanthan gum had the highest viscosities, regardless of concentration. During gastric simulation, viscosity was higher (P < 0.05) at 4 h than at 0 h for guar gum, psyllium, rice bran, and wheat bran. During small intestinal simulation, viscosities were higher (P < 0.05) between 3 and 9 h compared with 18 h for guar gum, oat bran, and rice bran. Guar gum, psyllium, and oat bran exhibited viscous characteristics throughout small intestinal simulation, indicating potential for these fibers to elicit blood glucose and lipid attenuation. Wheat and rice brans and wood cellulose did not exhibit viscous characteristics throughout small intestinal digestion; thus, they may be beneficial for laxation.