A complete human fecal flora and cultures of defined species obtained from fecal flora were investigated in vitro to determine their ability to ferment the dietary fiber pectin. Bacteroides thetaiotaomicron was tested as a pectin-degrading microorganism alone and in coculture with Escherichia coli. Macromolecular pectins with different degrees of esterification were used as substrates in microbial degradation studies. The levels of oligogalacturonic acids formed in batch cultures were estimated during a 24-or 48-h incubation period by using highperformance thin-layer chromatography and high-performance anion-exchange chromatography. The spectrum and the amount of unsaturated oligogalacturonic acids formed as intermediate products of pectin fermentation changed permanently in the culture media during incubation with the complete fecal flora. After 24 h, no oligogalacturonic acids were detected. The pectin-degrading activities of pure cultures of B. thetaiotaomicron were lower than the pectin-degrading activity of a complete fecal flora. Cocultures of B. thetaiotaomicron and E. coli exhibited intermediate levels of degradation activity. In pure cultures of E. coli no pectin-degrading activity was found. Additionally, the rate of pectin degradation was affected by the degree of esterification of the substrate. Saturated oligogalacturonic acids were not found during pectin fermentation. The disappearance of oligogalacturonic acids in the later stages of fermentation with both the complete fecal flora and B. thetaiotaomicron was accompanied by increased formation of short-chain fatty acids.In human nutrition, pectin is one of the most important sources of dietary fiber. It is present in vegetables and fruits as a component of the plant cell wall. Pectin consists mainly of long linear chains of ␣-1,4-glycoside-linked D-galacturonic acid (homogalacturonan; "smooth" regions) which are partially esterified with methanol. In addition, branched and complex pectic substances are present in the cell wall (rhamnogalacturonans I and II; "hairy" regions) (45). Like other types of dietary fiber, pectin is not depolymerized by endogenous gastrointestinal enzymes during passage through the stomach and the small intestine. A number of physiological effects of pectin or pectin-containing diets have been described; these effects include decreasing serum cholesterol levels (17), increasing fecal excretion of steroids (24), interacting with metal ions (25), and interacting with bile acids in vitro (11). These effects depend on the macromolecular state of pectin.In the colon, pectin is fermented more or less completely by the microflora, as shown previously (8,9,18,28,48). However, there have been only a few studies in which the intermediate steps in pectin degradation by gastrointestinal microorganisms have been examined. On the other hand, the end products of bacterial fermentation of pectin are well known; a spectrum of short-chain fatty acids (SCFA) and different gases (CO 2 , H 2 , H 2 S, CH 4 ) are formed. In some studies it was s...

We examined cereals and legume starches with different amylose contents, using X‐ray wide‐angle scattering. The parts of polymorphs in the crystalline regions and the crystallinity of the starches were determined. The high‐amylose starches hold 74.6%‐84.6% B‐type and 15.4%‐22.6% VH‐type. Crystallinity of high‐amylose starches is xc = 0.154–0.17. According to phase analysis of the scattering curve of wheat starch 6.8% B‐type and 93.2% A‐type are contained. Thus, in the crystalline phase wheat starch is more heterogeneous than maize starch. The residuary substance of heterogeneous hydrolysis of wheat starch at T1 =58°C is an insoluble sediment, which does contain already 17.1 % VH‐Amylose. This is the proof of the amylose‐lipid complex in the sediment. If the temperature of hydrolysis raised to 70°C, the VH,‐amylose proportion increased to 80.5%. Since the crystalline VH‐ structures are detectable during heterogeneous hydrolysis as from T1 = 58°C, they seem to have contained already in native starch.

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Polymer‐water interactions of a low DE maltodextrin and its Pn fractions are investigated by water vapour sorption and desorption measurements. The interpretation of the isotherms was done by the application of the three parameter Guggenheim‐Anderson‐de Boer equation and by the Flory‐Huggins theory. The polymer‐water interactions of the maltodextrin and its fractions exhibit strong dependence on Pn. The monolayer water content, the water uptake up to aw 0.95, the hysteresis effect, the water content of the transition powder‐gel under sorption conditions and the ability to form gels decrease with decreasing Pn. The water uptake above aw 0.95, the monolayer sorption enthalpy and solubility increase with decreasing Pn. The participation of molecular different fractions of the maltodextrin in polymer‐water interaction depends on the polymer concentration. Shelf live conditions for the maltodextrin are derived.