Wageningen, Netherlands
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Van Vliet T.,TI Food and Nutrition | Van Vliet T.,Wageningen University | Primo-Martin C.,TI Food and Nutrition
Journal of Texture Studies | Year: 2011

Hard solid foods encompass a large variety of dry products as well as products with high water content. Most of these foods have a cellular structure, which is generally characterized by connected fairly rigid cell walls, enclosing a fluid material that may be liquid-like (fruit and vegetables) or a gas (mainly manufactured cellular foods). Typical for many hard solid products is their brittle fracture behavior, mostly accompanied by acoustic emission. The latter characteristic is essential for their crispy or crunchy character. Other main texture attributes are hardness and brittleness and for fruits and vegetables juiciness. The latter requires that the liquid content of the cells is released during mastication. Aspects of fracture behavior of cellular food products, oral processing of these products, and the interplay between product characteristics and perception of some main texture attributes (hardness and crispness) will be discussed. PRACTICAL APPLICATIONS: It has become more and more clear that texture perception by consumers of hard solid (brittle) foods is based on the interplay between product structure, fracture behavior, oral processing and final grading by the brain. Better understanding of the relations between these aspects is essential for the production of healthy, tasteful food that is liked by consumers. This article focus on the interplay between physical properties of hard solid foods and oral processing in relation to the perception of selected texture attributes (hardness and crispness). © 2011 Wiley Periodicals, Inc.

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 | Year: 2014

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.

Pereira L.,University of Coimbra | Van De Velde F.,TI Food and Nutrition | Van De Velde F.,NIZO Food Research
Carbohydrate Polymers | Year: 2011

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.

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.

de Jongh H.H.J.,TI Food and Nutrition
Food Biophysics | Year: 2011

This work underlines that the role of water, its flow properties and its expulsion from the spatial network during oral processing, cannot be neglected in understanding the relation between gelled food structures and its sensory perception. It is shown that the properties of the included water phase of semi-solids are important as this phase can boost the water content in the oral cavity, and thereby increase taste sensations like sweetness. Moreover, the included water phase also plays a crucial role in how the energy exerted onto the gel during palating is used for either fracture, stored or dissipated in or by the network. To demonstrate this, a series of mixed whey protein/polysaccharide cold-set gels have prepared that were studied for a number of rheological and sensorial properties. Also, information on the expulsed serum volume during uniaxial compression and the breakdown pattern of these gels in the oral cavity was determined. It is shown that expulsion of serum from a gel during oral processing can be substantial and set by the morphology of the formed gel and the stiffness of the matrix. This expulsed serum volume is directly proportional to taste response. Moreover, it is found that both the viscous and elastic flow of serum through the gel upon deformation contribute to the perceived crumbliness of gels by lowering the recoverable energy. The elastic contribution of polysaccharides in the serum impairs with the energy available for fracture during oral processing, thereby affecting the sensory spreadability of the product. © 2011 Springer Science+Business Media, LLC.

Van Aken G.A.,TI Food and Nutrition | Van Aken G.A.,NIZO Food Research
Soft Matter | Year: 2010

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.

Baigts Allende D.,TI Food and Nutrition | de Jongh H.H.J.,TI Food and Nutrition | de Jongh H.H.J.,Wageningen University
Food Hydrocolloids | Year: 2015

This study aims to investigate the role of the ligation of steric moieties on the formation of junction zones during network formation of gelatin gels. The molecular conformational propensities, heat stability and mechanical properties of gradually chemically modified pork skin gelatin have been evaluated. To this end, glucose moieties are ligated to lysine residues on the protein using the Maillard reaction. It is shown that ligation of small sugar moieties only marginally impairs with triple helix formation and does not interfere with the mechanism of network formation. The Young's modulus (gel stiffness) and the fracture properties decrease with increasing degree of modification, but not the ability to reversibly store energy in the network. It is suggested that Maillardation affects the strand-strand interaction energy, but not necessarily the number of junction zones. A retained recoverable energy while the fracture properties can be affected allows industry to tailor food products in terms of their expected sensory performance. © 2015 Elsevier Ltd.

Primo-Martin C.,TI Food and Nutrition
Food Hydrocolloids | Year: 2012

Wheat starches with different degrees of cross-linking were used to study the effect of starch gelatinization in the batter and crust characteristics of deep-fried battered food. Pasting properties, viscosity and batter pick up as well as moisture and oil content and crispness of the fried crusts were evaluated. In batters prepared with a constant solids/water ratio, the cross-linked starches increased batter viscosity and consequently the batter pick up. Batters, with comparable viscosity were prepared by varying the solid/water ratio which gave the same batter pick up.The pasting properties of cross-linked starches showed that the higher the cross-linking the more resistant was the starch to gelatinization and granule disintegration. In batters with a constant solids/water ratio, batter with high cross-linked starch had more water loss during frying. Cross-linked starches had lower moisture content after storage and less oil was retained after frying. Crispness, measured instrumentally as sound intensity, was the highest for the high cross-linked starch at 1 and 20. min after frying.Batters prepared with the same viscosity were used to study the effect of cross-linked starches when the pick up was the same. To obtain comparable viscosities between the batters, the batter with native starch was prepared using the lowest mixing water content and the one with high cross-linked starch with the highest. The batter with the high cross-linked starch, although it had the highest addition of water, had the best crispness after frying.In conclusion, high cross-linking of wheat starch enhances crispness perception of deep-fried battered food. © 2011 Elsevier Ltd.

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.

Stieger M.,TI Food and Nutrition | Stieger M.,Wageningen University | Van de Velde F.,TI Food and Nutrition | Van de Velde F.,NIZO Food Research
Current Opinion in Colloid and Interface Science | Year: 2013

Food oral processing as the bridge between food texture, microstructure and sensory perception has gained enormous interest in the last decade. This review provides an overview of the role of the microstructure of soft- and semi-solid foods in food oral processing and sensory perception. Phase separated mixed protein-polysaccharide gels and emulsion-filled gels are described as suitable model foods to investigate food oral processing systematically. Special attention is given to the sensory perception of texture, taste and interactions thereof. Several approaches to reduce the salt and sugar content of semi- and soft-solid foods without compromising taste are reviewed. These reduction approaches are based on an understanding of food oral processing in relation to the microstructure of the foods and its breakdown. © 2013 Elsevier Ltd.

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