Fermentation of Arabinoxylan-Oligosaccharides, Oligofructose and their Monomeric Sugars by Hindgut Bacteria from Siberian Sturgeon and African Catfish in Batch Culture in vitro

The in vitro fermentation of two Non-Digestible Oligosaccharide (NDO) preparations, Arabinoxylan- Oligosaccharides (AXOS) and Oligofructose (OF), and their respective monomeric sugars, xylose and fructose, were investigated by hindgut microbiota of two major aquaculture fish species, Siberian sturgeon (Acipenser baerii) and African catfish (Clarias gariepinus). Inocula from the hindgut of both fish species were incubated for 48 h in bottles containing 1.0% of one of four substrates, i.e. AXOS, OF, xylose or fructose. Amounts and profiles of produced Short-Chain Fatty Acids (SCFAs) differed between the two fish species and substrates. The hindgut microbiota of Siberian sturgeon has a higher fermentation capacity than the microbiota from African catfish. Xylose was much easier fermented than AXOS by microbiota from Siberian sturgeon whereas OF was quicker fermented than fructose with African catfish inoculum. The SCFAs were dominated by acetic acid for both fish species and for all substrates. Fermentation of OF and fructose by hindgut microbiota of Siberian sturgeon also yielded high amounts of butyric and branched-chain fatty acids after 48 h incubation. Results of this study suggest that AXOS, OF, and their monomeric sugars have an impact on microbial fermentation activity of hindgut microbiota from Siberian sturgeon and African catfish in a substrate and species dependent manner

Enrichment of higher molecular weight fractions in inulin

Inulin (general formulas GF(n) and F-m with G = anhydroglucose and F = anhydrofructose) naturally occurs as a homologous series of oligo- and polysaccharides with different chain lengths. For reasons of growing interest in the food and pet food industries, the short chain inulins have to be separated from their long chain analogues because their properties (digestibility, prebiotic activity and health promoting potential, caloric value, sweetening power, water binding capacity, etc.) differ substantially. To study these properties in relation to the number average degree of polymerization (DPn), ultrafiltration, specific crystallization from aqueous solution, and precipitation from solvent/water mixtures were used to enrich native chicory and dahlia inulin in the higher molecular weight fractions. Depending on the membrane module used, the DPn of chicory inulin (DPn = 8.1) and dahlia inulin (DPn = 29) could be increased by ultrafiltration to a maximum value of, respectively, 22 and 43. With crystallization from aqueous solutions (25 degreesC), similar results were obtained but at a much higher yield. Finally, long chain inulin could be precipitated from aqueous solutions in the presence of high concentrations of methanol, ethanol, and acetone. Acetone demonstrated to be the best solvent system to increase the DPn, followed by ethanol and methanol. However, for safety reasons and food purposes, ethanol was evaluated to be the best choice. With ethanol, the DPn could be raised to 25 for chicory inulin and up to 40 for dahlia inulin

Physicochemical properties of potato and cassava starches and their mutants in relation to their structural properties

Physicochemical properties [swelling power (SP), pasting behaviour and retrogradation] of five wild type (wt), five amylose free (amf), four high-amylose (ha) potato starches (ps) and one wt and amf cassava starch (cs) were investigated. While swelling of wtps occurred in two phases, amfps showed a very fast swelling and no gel of swollen granules was observed at higher temperatures (>90 °C). Haps underwent only restricted swelling. SP of cassava starches were lower than those of potato starches. Wtps leached mainly amylose (AM) during heating at low temperatures. Molecules of higher molecular weight (MW) leached out at higher temperatures. Longer amylopectin (AP) chains [degree of polymerisation (DP) > 18] inhibited swelling while short chains (DP 18) depressed peak viscosity, while short chains (DP <14) increased peak viscosity for both concentrations. At 8.0%, peak viscosity increased with starch granule size. After 1 day of storage of gelatinised starch suspensions, wtps and especially amfps showed only limited AP retrogradation. In contrast, the high enthalpies of retrograded AP (¿Hretro) and peak and conclusion temperatures of retrogradation (Tp,retro and Tc,retro) of haps suggested partial cocrystallisation between AM and AP. Chains with DP 18–25 seemed to be more liable to AP retrogradation. Wtcs and amfcs did not retrograde at room temperature