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The colonic microbial metabolism is a key contributor to uremic retention solutes accumulating in patients with CKD, relating to adverse outcomes and insulin resistance. Whether prebiotics can reduce intestinal generation of these microbial metabolites and improve insulin resistance in CKD patients not yet on dialysis remains unknown. We performed a randomized, placebo-controlled, double-blind, cross-over study in 40 patients with eGFR between 15 and 45 ml/min/1.73 m2. Patients were randomized to sequential treatment with prebiotic arabinoxylan oligosaccharides (AXOS) (10 g twice daily) and maltodextrin for 4 weeks, or vice versa, with a 4-week wash-out period between both intervention periods. Serum levels and 24h urinary excretion of p-cresyl sulfate, p-cresyl glucuronide, indoxyl sulfate, trimethylamine N-oxide and phenylacetylglutamine were determined at each time point using liquid chromatography-tandem mass spectrometry. In addition, insulin resistance was estimated by the homeostatic model assessment (HOMA-IR). A total of 39 patients completed the study. We observed no significant effect of AXOS on serum p-cresyl sulfate (P 0.42), p-cresyl glucuronide (P 0.59), indoxyl sulfate (P 0.70) and phenylacetylglutamine (P 0.41) and a small, albeit significant decreasing effect on serum trimethylamine N-oxide (P 0.04). There were neither effect of AXOS on 24h urinary excretion of p-cresyl sulfate (P 0.31), p-cresyl glucuronide (P 0.23), indoxyl sulfate (P 0.87) and phenylacetylglutamine (P 0.43), nor on 24h urinary excretion of trimethylamine N-oxide (P 0.97). In addition, we observed no significant change in HOMA-IR (P 0.93). In conclusion, we could not demonstrate an influence of prebiotic AXOS on microbiota derived uremic retention solutes and insulin resistance in patients with CKD not yet on dialysis. Further study is necessary to elucidate whether prebiotic therapy with other characteristics, higher cumulative exposure or in different patient populations may be of benefit. Clinicaltrials.gov NCT02141815.

Ascorbic acid (AH2) is a commonly used additive in food products. In wheat breadmaking, it is, for example, added to flour for its dough strengthening and bread volume-enhancing effects. While these bread property-enhancing effects are well known, the final chemical fate of AH2 in breadmaking applications remains nearly undocumented. This study tries to shed light on the chemical fate of AH2 in wheat breadmaking by investigating the chemical and enzymatic conversion of AH2 and its reaction products using 13C NMR spectroscopy in combination with AH2 labelled with 13C on the C3 carbon. Following the chemical conversion of AH2 as function of time, in ultra-pure water, tap water, and wheat flour extracts, in the presence and absence of dissolved O2 and glutathione (GSH), the specific impact of the presence of trace metal ions, dissolved oxygen and endogenous GSH on the oxidation of AH2 could be elucidated.

In this study, the prebiotic potential of arabinoxylan oligosaccharides (AXOS) was compared with inulin in two simulators of the human intestinal microbial ecosystem. Microbial breakdown of both oligosaccharides and short-chain fatty acid production was colon compartment specific, with ascending and transverse colon being the predominant site of inulin and AXOS degradation, respectively. Lactate levels (+5.5 mM) increased in the ascending colon during AXOS supplementation, while propionate levels (+5.1 mM) increased in the transverse colon. The concomitant decrease in lactate in the transverse colon suggests that propionate was partially formed over the acrylate pathway. Furthermore, AXOS supplementation strongly decreased butyrate in the ascending colon, this in parallel with a decrease in Roseburia spp. and Bacteroides/Prevotella/Porphyromonas (-1.4 and -2.0 log CFU) levels. Inulin treatment had moderate effects on lactate, propionate and butyrate levels. Denaturing gradient gel electrophoresis analysis revealed that inulin changed microbial metabolism by modulating the microbial community composition. In contrast, AXOS primarily affected microbial metabolism by 'switching on' AXOS-degrading enzymes (xylanase, arabinofuranosidase and xylosidase), without significantly affecting microbial community composition. Our results demonstrate that AXOS has a higher potency than inulin to shift part of the sugar fermentation toward the distal colon parts. Furthermore, due to its stronger propionate-stimulating effect, AXOS is a candidate prebiotic capable of lowering cholesterol and beneficially affecting fat metabolism of the host.

Normal-phase high-performance liquid chromatography (HPLC) is widely used in combination with evaporative light scattering detection (ELSD) for separating and detecting lipids in various food samples. ELSD responses of different lipids were evaluated to elucidate the possibilities and challenges associated with quantification by means of HPLC-ELSD. Not only the number and type of polar functional groups but also the chain length and degree of unsaturation of (free or esterified) fatty acids (FAs) had a significant effect on ELSD responses. Tripalmitin and trilinolein yielded notably different ELSD responses, even if their constituting free FAs produced identical responses. How FA structure impacts ELSD responses of free FAs is thus not predictive for those of triacylglycerols and presumably other lipids containing esterified FAs. Because ELSD responses of lipids depend on the identity of the (esterified) FA(s) which they contain, fully accurate lipid quantification with HPLC-ELSD is challenging and time-consuming. Nonetheless, HPLC-ELSD is a good and fast technique to semi-quantitatively compare the levels of different lipid classes between samples of comparable FA composition. In this way, lipid profiles of different flours from near-isogenic wheat lines could be compared.

Referee: Dr. Frank Bekes, Grain Quality Research Laboratory, CSIRO Division of Plant Industry, 51 Delhi Road, (PO Box 7), North Ryde NSW 1670, Australia The unique breadmaking properties of wheat are generally ascribed to the visco-elastic properties of its gluten proteins. While monomeric gluten proteins (gliadin) show viscous behavior, polymeric gluten proteins (glutenin) are elastic. The unique elasticity of glutenin results to a large extent from its polymeric nature. Glutenin is a highly heterogeneous mixture of polymers consisting of a number of different high- and low-molecular-weight glutenin subunits linked by disulfide bonds. Although glutenin obviously is the major polymeric protein in wheat, other polymeric proteins occur as well. Their importance in breadmaking may be underestimated. Nevertheless, variations in both quantity and quality of glutenin strongly determine variations in breadmaking performance. Structural features of different classes of glutenin subunits are described. Variations in glutenin quality may result from variations in its (1) structure, (2) size distribution, and (3) subunit composition. Some hypotheses on glutenin structure and current insights into the role of glutenin size distribution are evaluated. Finally, different ways in which variation in glutenin composition may directly or indirectly (by affecting glutenin structure and/or size distribution) influence glutenin quality are discussed.

Successful sucrose replacement in cake systems requires thorough understanding of its functionality. Time-domain 1 H NMR showed that water in the viscous aqueous phase isolated from cake batter by ultracentrifugation [i.e. the batter liquor (BL)] exhibits low mobility by its low T 2 relaxation time (T 2,D RT). This is due to its interactions with sucrose or sucrose replacers. The T 2,D RT itself is positively related with the effective volumetric hydrogen bond density of sucrose or sucrose replacers. Sucrose additionally co-determines the quantity and viscosity of cake BL and thereby how much air the batter contains at the end of mixing. Like sucrose, maltitol and oligofructose provide adequate volumes of BL with low water mobility and thus sufficient air in the batter, while the rather insoluble mannitol and inulin do not. Differential scanning calorimetry and rapid viscosity analysis revealed, however, that, in contrast to sucrose and maltitol, oligofructose fails to provide appropriate timings of starch gelatinisation and protein denaturation, resulting in poor cake texture. The shortcomings of mannitol and oligofructose in terms of respectively ensuring appropriate gas content in batter and biopolymer transitions during baking can be overcome by using mixtures thereof. This work shows that successful sucrose substitutes or substitute mixtures must provide sufficient BL with low water mobility and ensure appropriate timings of starch and protein biopolymer transitions during baking.

The fine molecular structure of starch governs its functionality and digestibility, and enzymatic approaches can be utilized to tailor its properties. The aim of this study was to investigate the in situ modification of starch by amylomaltase (AMM) from Thermus thermophilus in model starch systems subjected to hydrothermal treatments under standardized conditions and the relationship between molecular structure, rheological properties and in vitro digestibility. When low dosages of AMM were added to a wheat starch suspension prior to submitting it to a temperature-time profile in a Rapid Visco Analyzer, the increased peak viscosity observed was attributed to partial depolymerization of amylose, which facilitated starch swelling and viscosity development. At higher dosages, the effect was smaller. The low cold paste viscosity as a result of the activity of AMM reflected substantial amylose depolymerization. At the same time, amylopectin chains were substantially elongated. The longer amylopectin chains were positively correlated (R2 = 0.96) with the melting enthalpies of retrograded starches, which, in turn, were negatively correlated with the extent (R2 = 0.92) and rate (R2 = 0.79) of in vitro digestion. It was concluded that AMM has the potential to be used to deliver novel starch functionalities and enhance its nutritional properties.

The main sponge cake ingredients are flour, sucrose, eggs and leavening agents. Exogenous lipids (e.g., monoacylglycerols) are often used to increase air–liquid interface stability in the batter. There is a consumer trend to avoid foods containing such additives. We here reasoned that egg yolk may be an alternative source of surface-active lipids and set out to study the role of egg yolk lipids during sponge cake making. This was done by relocating or removing them prior to batter preparation using ethanol treatments and examining how this affects cake (batter) properties and structure setting during baking. Most egg yolk lipids occur within spherical low-density lipoproteins (LDLs) which were disintegrated by the ethanol treatments. Results showed that egg yolk lipids impact air–liquid interface stability and less so cake structure setting. To prepare high-quality sponge cakes by multistage mixing preferably intact LDLs or, alternatively, their components are needed to incorporate sufficient air during mixing and to stabilize it after mixing. It was also shown that the batter contains intact LDLs in the continuous phase and disintegrated LDLs at air–liquid interfaces. Sponge cake contains intact LDLs in the cake matrix, disintegrated LDLs at air–crumb interfaces and disintegrated LDLs incorporated into the protein network.

Short chain fatty acids (SCFA), including acetate, propionate, and butyrate, are produced during bacterial fermentation of undigested carbohydrates in the human colon. In this study, we applied a stable-isotope dilution method to quantify the in vivo colonic production of SCFA in healthy humans after consumption of inulin. Twelve healthy subjects performed a test day during which a primed continuous intravenous infusion with [1-13C]acetate, [1-13C]propionate and [1-13C]butyrate (12, 1.2 and 0.6 μmol·kg−1·min−1, respectively) was applied. They consumed 15 g of inulin with a standard breakfast. Breath and blood samples were collected at regular times during the day over a 12 h period. The endogenous rate of appearance of acetate, propionate, and butyrate was 13.3 ± 4.8, 0.27 ± 0.09, and 0.28 ± 0.12 μmol·kg−1·min−1, respectively. Colonic inulin fermentation was estimated to be 137 ± 75 mmol acetate, 11 ± 9 mmol propionate, and 20 ± 17 mmol butyrate over 12 h, assuming that 40%, 10%, and 5% of colonic derived acetate, propionate, and butyrate enter the systemic circulation. In conclusion, inulin is mainly fermented into acetate and, to lesser extents, into butyrate and propionate. Stable isotope technology allows quantifying the production of the three main SCFA in vivo and proved to be a practical tool to investigate the extent and pattern of SCFA production.

In vivo experiments were conducted to verify whether arabinoxylooligosaccharides (AXOS) obtained as low molecular mass compounds by enzymic hydrolysis from wheat bran arabinoxylan (AX) can exert nutritional effects. Two feeding trials were performed on chickens fed diets with either wheat or maize as the main component. Supplementation of bran AXOS at either 0.5% (w/w) to the wheat-based diet or at 0.25% (w/w) to the maize-based diet diets significantly (P < 0.05) improved the feed conversion rate without increasing the body weight of the animals, thus pointing to improved nutrient utilization efficiency. The positive effect of bran AXOS supplementation on feed utilization efficiency was similar to that obtained by adding an AX-degrading xylanase directly to the wheat-based diet. No significant effect on feed utilization efficiency was obtained with another type of nondigestible oligosaccharide such as fructooligosaccharides (FOS) derived from chicory roots. Bran AXOS significantly increased the level of bifidobacteria but not total bacteria in the caeca of the chickens, an effect not observed with either xylanase or FOS addition. These data suggest that bran AXOS have beneficial nutritional effects and may act as prebiotics.