Systemic availability and metabolism of colonic-derived short-chain fatty acids in healthy subjects: a stable isotope study

The short-chain fatty acids (SCFAs), acetate, propionate and butyrate, are bacterial metabolites that mediate the interaction between the diet, the microbiota and the host. In the present study, the systemic availability of SCFAs and their incorporation into biologically relevant molecules was quantified. Known amounts of 13C-labelled acetate, propionate and butyrate were introduced in the colon of 12 healthy subjects using colon delivery capsules and plasma levels of 13C-SCFAs 13C-glucose, 13C-cholesterol and 13C-fatty acids were measured. The butyrate-producing capacity of the intestinal microbiota was also quantified. Systemic availability of colonic-administered acetate, propionate and butyrate was 36%, 9% and 2%, respectively. Conversion of acetate into butyrate (24%) was the most prevalent interconversion by the colonic microbiota and was not related to the butyrate-producing capacity in the faecal samples. Less than 1% of administered acetate was incorporated into cholesterol and <15% in fatty acids. On average, 6% of colonic propionate was incorporated into glucose. The SCFAs were mainly excreted via the lungs after oxidation to 13CO2, whereas less than 0.05% of the SCFAs were excreted into urine. These results will allow future evaluation and quantification of SCFA production from 13C-labelled fibres in the human colon by measurement of 13C-labelled SCFA concentrations in blood

Production, structure, physicochemical and functional properties of maize, cassava, wheat, potato and rice starches

© 2014 Wiley-VCH Verlag GmbH & Co. KGaA. In 2012, the world production of starch was 75 million tons. Maize, cassava, wheat and potato are the main botanical origins for starch production with only minor quantities of rice and other starches being produced. These starches are either used by industry as such or following some conversion. When selecting and developing starches for specific purposes, it is important to consider the differences between starches of varying botanical origin. Here, an overview is given of the production, structure, composition, morphology, swelling, gelatinisation, pasting and retrogradation, paste firmness and clarity and freeze-thaw stability of maize, cassava, wheat, potato and rice starches. Differences in properties are largely defined by differences in amylose and amylopectin structures and contents, granular organisation, presence of lipids, proteins and minerals and starch granule size.status: publishe

Direct evidence for the non-additive gelatinization in binary starch blends: A case study on potato starch mixed with rice or maize starches

Potato starch (PS) was blended with maize (MS), waxy maize (WMS), rice (RS) or waxy rice (WRS) starch in different ratios. Gelatinization of the blends was studied at intermediate water content (1:1 starch dry matter:water). In the pure state, PS gelatinizes at slightly lower temperature than the other components. The pure systems as well as the blends display bimodal gelatinization with so-called G (low temperature) and M1 (high temperature) endotherms in Differential Scanning Calorimetry (DSC). Gelatinization of the blend, however, cannot be understood as a proportional superposition of the gelatinization of the pure components. Time-resolved synchrotron wide angle X-ray diffraction (WAXD) was used to uncover the gelatinization of each starch in the blend separately, thereby exploiting the fact that PS contains B-type and the other species A-type crystals. Very clearly, PS gelatinizes more predominantly within the G, and the other component within the M1 endotherm in the blends than when gelatinized alone. This can be understood in terms of competition for water, needed to induce gelatinization. Finally, a novel DSC based method was proposed to approach gelatinization of each starch component within the blend separately. The results are qualitatively in agreement with those obtained from the more rigorous WAXD based method.status: publishe

What makes starch from potato (Solanum tuberosumL.) tubers unique: A review

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Molecular and Morphological Aspects of Annealing-Induced Stabilization of Starch Crystallites

A unique series of potato (mutant) starches with highly different amylopectin/amylose (AP/AM) ratios was annealed in excess water at stepwise increasing temperatures to increase the starch melting (or gelatinization) temperatures in aqueous suspensions. Small-angle X-ray scattering (SAXS) experiments revealed that the lamellar starch crystals gain stability upon annealing via thickening for high-AM starch, whereas the crystal surface energy decreases for AM-free starch. In starches with intermediate AP/AM ratio, both mechanisms occur, but the surface energy reduction mechanism prevails. Crystal thickening seems to be associated with the cocrystallization of AM with AP, leading to very disordered nanomorphologies for which a new SAXS data interpretation scheme needed to be developed. Annealing affects neither the crystal internal structure nor the spherulitic morphology on a micrometer length scale

Distribution of Minerals in Wheat Grains (<i>Triticum aestivum</i> L.) and in Roller Milling Fractions Affected by Pearling

The distribution of minerals in (pearled) wheat grains was measured by synchrotron X-ray fluorescence, and the impact of pearling (0, 3, 6, 9, and 12% by weight) on the mineral composition of flour, shorts, and bran was identified by ICP-MS. The xylem mobile elements (Mn, Si, Ca, and Sr) dominated in the outermost bran layers, while the phloem mobile elements (K, Mg, P, Fe, Zn, and Cu) were more concentrated in the aleurone. Pearling lowered the concentrations of xylem mobile elements and increased the concentrations of most phloem mobile elements in the pearled grains. Molybdenum, Cd, and especially Se were more evenly distributed, and pearling affected their concentrations in milling products less. Pearling (3%) increased the concentration of several nutrients (P, Zn, Cu) in the flour because the bran fractions reaching the flour are enriched in aleurone. The correlations of concentrations of Mg, Fe, Zn, and Cu with that of P suggested their association with phytate

Systemic availability and metabolism of colonic-derived short-chain fatty acids in healthy subjects: a stable isotope study

The short-chain fatty acids (SCFAs) are bacterial metabolites produced during the colonic fermentation of undigested carbohydrates, such as dietary fibre and prebiotics, and can mediate the interaction between the diet, the microbiota and the host. We quantified the fraction of colonic administered SCFAs that could be recovered in the systemic circulation, the fraction that was excreted via the breath and urine, and the fraction that was used as a precursor for glucose, cholesterol and fatty acids. This information is essential for understanding the molecular mechanisms by which SCFAs beneficially affect physiological functions such as glucose and lipid metabolism and immune function.status: publishe