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Apeldoorn, Netherlands

Pereira L.,University of Coimbra | Van De Velde F.,TI Food and Nutrition | Van De Velde F.,NIZO food research
Carbohydrate Polymers

Eight carrageenophytes from the Centre and North coast of Portugal, representing seven genera and three families of Gigartinales, were studied in 15 different coastal stations in a geographic study, from Baleal (Peniche), in the central zone, to Moledo, in the northern zone. In order to characterize the different carrageenan types, 1H NMR spectroscopy was used to identify and quantify the different carrageenan fractions in the extracted phycocolloids (both water and alkali extractions). Thereby, detailed information concerning the properties and structure of these polysaccharides at molecular level was revealed. Based on the results of the analysis of the carrageenan types, the following conclusions were made: female gametophytes and non-fertile thalli of Chondrus crispus, Mastocarpus stellatus, Chondracanthus teedei var. lusitanicus, Gigartina pistillata, Chondracanthus acicularis and Gymnogongrus crenulatus, presented a varying degrees of kappa-iota hybrid carrageenan (co-polymers of kappa-iota carrageenan). The kappa/iota ratio ranged from 0 to 2.2. The carrageenans extracted from Ahnfeltiopsis devoniensis were mainly iota-carrageenan, but some geographic variations in the composition of carrageenans were found. Calliblepharis jubata contained carrageenans of iota-type in all reproductive stages. Lambda-family carrageenans were found in tetrasporophytes of C. cripus (lambda), M. stellatus (lambda), C. teedei var. lusitanicus (hybrid xi-theta), C. acicularis (hybrid xi-theta) and G. pistillata (hybrid xi-lambda). © 2010 Elsevier Ltd. All rights reserved. Source

An increased intestinal permeability is associated with several diseases. Previously, we have shown that dietary Ca decreases colonic permeability in rats. This might be explained by a calcium-phosphate-induced increase in luminal buffering capacity, which protects against an acidic pH due to microbial fermentation. Therefore, we investigated whether dietary phosphate is a co-player in the effect of Ca on permeability. Rats were fed a humanised low-Ca diet, or a similar diet supplemented with Ca and containing either high, medium or low phosphate concentrations. Chromium-EDTA was added as an inert dietary intestinal permeability marker. After dietary adaptation, short-chain fructo-oligosaccharides (scFOS) were added to all diets to stimulate fermentation, acidify the colonic contents and induce an increase in permeability. Dietary Ca prevented the scFOS-induced increase in intestinal permeability in rats fed medium- and high-phosphate diets but not in those fed the low-phosphate diet. This was associated with higher faecal water cytotoxicity and higher caecal lactate levels in the latter group. Moreover, food intake and body weight during scFOS supplementation were adversely affected by the low-phosphate diet. Importantly, luminal buffering capacity was higher in rats fed the medium- and high-phosphate diets compared with those fed the low-phosphate diet. The protective effect of dietary Ca on intestinal permeability is impaired if dietary phosphate is low. This is associated with a calcium phosphate-induced increase in luminal buffering capacity. Dragging phosphate into the colon and thereby increasing the colonic phosphate concentration is at least part of the mechanism behind the protective effect of Ca on intestinal permeability. Source

Velasquez J.,Zernike Institute for Advanced Materials | Schuurman-Wolters G.,Zernike Institute for Advanced Materials | Birkner J.P.,Zernike Institute for Advanced Materials | Abee T.,TI Food and Nutrition | And 2 more authors.
Molecular Microbiology

A critical event during spore germination is the release of Ca-DPA (calcium in complex with dipicolinic acid). The mechanism of release of Ca-DPA through the inner membrane of the spore is not clear, but proteins encoded by the Bacillus subtilisspoVA operon are involved in the process. We cloned and expressed the spoVAC gene in Escherichia coli and characterized the SpoVAC protein. We show that SpoVAC protects E.coli against osmotic downshift, suggesting that it might act as a mechanosensitive channel. Purified SpoVAC was reconstituted in unilamellar lipid vesicles to determine the gating mechanism and pore properties of the protein. By means of a fluorescence-dequenching assay, we show that SpoVAC is activated upon insertion into the membrane of the amphiphiles lysoPC and dodecylamine. Patch clamp experiments on E.coli giant spheroplast as well as giant unilamellar vesicles (GUVs) containing SpoVAC show that the protein forms transient pores with main conductance values of about 0.15 and 0.1 nS respectively. Overall, our data indicate that SpoVAC acts as a mechanosensitive channel and has properties that would allow the release of Ca-DPA and amino acids during germination of the spore. © 2014 John Wiley & Sons Ltd. Source

Van Aken G.A.,TI Food and Nutrition | Van Aken G.A.,NIZO food research
Soft Matter

This paper introduces a mechanistic approach to relate the sensations of touch by epithelial surfaces of for example skin, eye or mouth to the material properties of the substrate. The approach is to model the hydrodynamic and frictional forces exerted by the substrate onto the surfaces, which are deformable and compliant to these forces. Subsequently these forces are related to the neurological responses of the mechanoreceptors buried in these surfaces. The potential of the approach is illustrated for textural perception of food materials in the mouth. It leads to several concepts for textural perception in the mouth, some of which have been demonstrated previously and some of which are new. As a first example, the branching into high and low viscosity regimes for thickness perception found experimentally can be linked directly to the detection limit of the neural receptors. As a second example, by taking into account the intrinsic roughness and deformability of the papilla surface, estimates are obtained for the cross-over between the hydrodynamic friction regime, where the papilla tips are lubricated by a thin liquid film (smooth mouthfeel), and the boundary friction regime, where the papilla tips are in direct contact with the opposing surface of the palate (rough mouthfeel). This has implications for the role of viscosity on smoothness and astringency sensations. As a final example, the model suggests that the sensation of hard particles (grittiness) can be suppressed by increasing the viscosity of the medium, which is in agreement with experimental findings from sensory studies. © 2010 The Royal Society of Chemistry. Source

The gastrointestinal tract is a complex and intricate machinery to process and absorb nutrients from food in a highly controlled and efficient way. One of the main purposes is to provide essential nutrients (proteins, fats, and carbohydrates) to the blood in a soluble form that can be further processed by the body. For this reason, the food is digested by various enzymes and brought into a state in which it can be absorbed by the small intestines. The proliferation of obesity in the Western world has motivated several research groups to study the digestion process, ultimately to control food intake by food design. This paper reviews the literature related to the digestion of food emulsions, describing in detail the organization and function of the various organs of the gastrointestinal tract, the way these organs cooperate and how this cooperation is regulated by physiological signals. The insight may help to cross the bridge toward designed food structuring from a food-engineering and physical-chemical perspective. Based on the physiological understanding of fat digestion, opportunities to affect the digestion of triglycerides by food structure and composition, stability under stomach conditions, and delayed digestion and absorption in the small intestine are identified. © 2010 Springer Science+Business Media, LLC. Source

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