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Abstract: Whey protein isolate (WPI)/polysaccharide mixed gels used in the current study formed homogeneous and phase separated microstructures as visualized by confocal laser scanning microscopy (CLSM). The latter can be further classified into protein continuous, bicontinuous and coarse stranded microstructures. Quantitative descriptive analysis (QDA) was used to evaluate sensory properties of the gels. The gels were subjected to large deformations by uniaxial compression. The microstructure affects the gels breakdown properties as well as serum release which occurred during compression of the gels. Protein continuous and bicontinuous gels fractured through the protein network. They fractured along only a few crack planes, whereas in coarse stranded gels cracks were formed at many places which was accompanied by coarsening of the protein network. Serum release was strongly correlated with gels porosity. Highly porous gels, i.e., bicontinuous and coarse stranded ones, released higher amount of serum than the other gels. In addition, serum release affected large deformation and fracture properties of the gels. QDA panel tests showed that breakdown mechanisms and serum release were the major factors in sensory perception of the gels. Gels fracturing only along a few planes were perceived as firm and crumbly whereas gels showing multiple fracture events were perceived as spreadable. Gels releasing high amount of serum were perceived as watery. The study confirmed the essential role of microstructure in sensory perception of mixed gels. [Copyright &y& Elsevier]

Abstract: Release of serum is important for many food systems such as meat products and its replacers, gels, vegetables and fruit, where serum release plays a clear role in the perception of juiciness. Nevertheless, this phenomenon and its consequences for large deformation and fracture behaviour have not been studied extensively for semi-solid food systems. It has been avoided in the experimental setup or it even has been neglected in analysis of the data. In this study mixed whey protein isolate/gellan gum gels were used as model systems. Gels were subjected to uniaxial compression and evaluated sensorically by a quantitative descriptive analysis panel. The latter showed that serum release was a dominant factor in sensory perception of the gels regarding mouthfeel attributes as slippery and watery. Compression experiments showed that serum release is related to microstructural characteristics of the gels. The serum release can be described by flow through a porous medium, starting from the Darcy''s equation. It was demonstrated that the large deformation mechanical properties of the gels can be described better by correcting for the effect of serum release. Moreover, a relation between serum release, gel microstructure and sensory evaluation was established. [Copyright &y& Elsevier]

BACKGROUND: A high plasma concentration of total homocysteine (tHcy) is associated with increased risk of cardiovascular disease. A high protein intake and hence a high intake of methionine-the sole dietary precursor of homocysteine-may raise plasma tHcy concentrations. OBJECTIVES: We studied whether high intake of protein increases plasma concentrations of tHcy in the fasting state and throughout the day. DESIGN: We conducted a randomized, dietary controlled, crossover trial in 20 healthy men aged 18-44 y. For 8 d, men consumed a controlled low-protein diet enriched with either a protein supplement [high-protein diet (21% of energy as protein)] or an isocaloric amount of short-chain glucose polymers [low-protein diet (9% of energy as protein)]. After a 13-d washout period, treatments were reversed. On days 1 and 8 of each treatment period, blood was sampled before breakfast (fasting) and throughout the day. RESULTS: Fasting tHcy concentrations did not differ significantly after the 1-wk high-protein and the 1-wk low-protein diets. The high-protein diet resulted in a significantly higher area under the 24-h homocysteine-by-time curves compared with the low-protein diet, both on day 1 (difference: 45.1 h x mumol/L; 95% CI: 35.3, 54.8 h x mumol/L; P < 0.0001) and on day 8 (difference: 24.7 h x mumol/L; 95% CI: 15.0, 34.5 h x mumol/L; P < 0.0001). CONCLUSIONS: A high-protein diet increases tHcy concentrations throughout the day but does not increase fasting tHcy concentrations. As previously shown, the extent of the tHcy increase is modified by the amino acid composition of the protein diet. The clinical relevance of this finding depends on whether high concentrations of tHcy-particularly postprandially-cause cardiovascular disease. Copyright © 2005 American Society for Clinical Nutrition [ABSTRACT FROM AUTHOR]

The concentration dependence of dynamic moduli of soy protein gels was studied for different protein preparations (soy protein isolate), purified glycinin and a β-conglycinin rich fraction) at various pHs and salt concentrations. The concentration dependence of the storage modulus of glycinin and β-conglycinin gels was similar to that of SPI gels. For SPI, the critical protein concentration for gelation was estimated to be between 3 and 5% at pH 7.6 (0.2 M NaCl), and between 6.5 and 8% at pH 7 (0 M NaCl), and 0% at pH 5.2 and pH 3.8 (0.2 M NaCl). At the high pHs the critical protein concentration decreased with the stage in the heating cycle. Relating the experimental data to a fractal model, both rheological and permeability measurements resulted in a consistent value for the fractal dimensionality Df (=2.3) for SPI gels at pH 3.8 and 0.2 M NaCl. At pH 5.2 and 7.6 (0.2 M NaCl), and pH 7 (0 M NaCl), the concentration dependence of the modulus could not be analysed theoretically. Likely this is due to rearrangements in the spatial structure of the network starting directly after a percolating network was formed. It causes the concentration dependence to depend on ageing time. [Copyright &y& Elsevier]

This paper reports on creaming and flocculation in 10% (w/w) oil-in-water emulsions, stabilised by β-lactoglobulin (β-lg) and flocculated by dextran. Dextran and an additional amount of β-lg were added at various concentrations after emulsion formation. A substantial effect of the β-lg concentration was observed. At higher β-lg concentrations, a larger dextran concentration was required to induce network formation. This effect was explained by a retardation of the flocculation process at larger β-lg concentrations, shown by diffusing wave spectroscopy (DWS). This retardation was caused by the unexpectedly high apparent viscosity at low shear-rates of mixed solutions of β-lg and dextran. [Copyright &y& Elsevier]

The objectives of the present study were to compare the bioavailability of vitamin A from liver paste and from a vitamin A supplement at three nutritionally relevant levels of intake, and to estimate levels of "safe" intake based on concentrations of retinoic acid and its metabolites in plasma after a single dose of vitamin A from liver paste. Women (n = 35; 19-47 y of age) consumed 3.0, 7.5 or 15 mg vitamin A as liver paste or as a vitamin A supplement with a test meal in a randomized design, with a combined crossover (two sources) and parallel approach (three dosages). Retinyl esters and retinoic acid (RA) metabolites were quantified in blood samples at 2-24 h after dosing. The areas under the time-response curves (AUC) were calculated to evaluate responses in plasma vitamin A after intake of liver paste and the vitamin A supplements. For retinyl esters, the AUC was significantly affected by the dosage, but not by the source. The formation of 13-cis-RA, 13-cis-4-oxo-RA, and to a lesser extent all-trans-RA was significantly higher after consumption of liver paste compared with the supplement, especially at higher dosages. Long-term baseline concentrations of retinol were not affected by a single intake of vitamin A. In conclusion, the bioavailability of vitamin A from single doses of liver paste and a vitamin A supplement does not differ, but the plasma concentrations of RA metabolites are higher after intake of liver paste. Thus, pregnant women should indeed limit the intake of vitamin A from liver products. [ABSTRACT FROM AUTHOR]

The potential benefits of a high fruit and vegetable intake on the antioxidant status and on relevant biomarkers of oxidative damage to lipids, proteins and DNA and on (functional) markers of oxidative stress were evaluated. A randomized, free living, open placebo-controlled cross-over trial of 3 wk, with a 2-wk washout period between treatments, was performed in a group of 22 male smokers with a relatively low vegetable and fruit intake using a vegetable burger and fruit drink. The vegetable burger and fruit drink increased serum levels of vitamin C, alpha-carotene, beta-carotene, beta-cryptoxanthin and zeaxanthin and plasma total antioxidant capacity. However, no effects were demonstrated on any marker of oxidative damage to lipids (malondialdehyde F(2)-isoprostane) proteins (carbonyls) and DNA (Comet assay) and (functional) markers of oxidative stress (reduced/oxidized glutathione ratio, glutathione-S-transferase alpha, glutathione-S-transferase pi and nuclear transcription factor-kappaB). Apparently, these increased levels of antioxidants in serum were not sufficiently high to show beneficial changes with the selected biomarkers. Alternatively, oxidative stress in male smokers with a relatively low fruit and vegetable intake might have been still too low to demonstrate a beneficial effect of antioxidants. [ABSTRACT FROM AUTHOR]

The effects of lutein and lycopene on beta-carotene absorption and cleavage were investigated in 12 male subjects. Responses of carotenoids and retinyl palmitate in the triacylglycerol-rich lipoprotein (TRL) fraction after a separate 15-mg beta-carotene dose were compared with those after a dose of 15 mg beta-carotene combined with 15 mg lycopene or lutein (given as natural concentrates or extracts). After combined dosing with lutein, the areas under the curve (AUCs) of beta-carotene and retinyl palmitate in the TRL fraction, adjusted for the triacylglycerol response, were 66% (P = 0.019) and 74% (P < 0.059), respectively, compared with 100% after dosing with beta-carotene alone. After combined dosing with lycopene these percentages were 90% and 101%, respectively (NS). Beta-carotene conversion, estimated from the ratio between the AUC for retinyl esters and beta-carotene, assuming eccentric cleavage, was 69%, 71%, and 72% for treatment with only beta-carotene, beta-carotene combined with lycopene, and beta-carotene combined with lutein, respectively. In addition, a pilot study was performed to evaluate application of TRL response curves to measure absorption of carotenoids from vegetable sources (15 mg carotenoid as carrots, spinach, and tomato paste). As compared with the carotenoid concentrates, responses were considerably lower or hardly measurable (beta-carotene and retinyl palmitate after carrots, lutein after spinach), except for lycopene and retinyl palmitate after a single dose of tomato paste. In conclusion, this study showed that lutein, but not lycopene, negatively affected beta-carotene absorption when given simultaneously with beta-carotene but apparently had no effect on beta-carotene cleavage. Copyright (c) 1998 American Society for Clinical Nutrition [ABSTRACT FROM AUTHOR]

Abstract: This paper describes the relation between crumbliness of whey proteins/polysaccharide mixed gels and their physical properties. Crumbly sensation relates strongly to the breakdown behaviour of the gels, which is primarily determined by their viscoelastic properties. These properties result from the balance between elastically stored energy and energy dissipation during deformation. The stored energy is determined as the percentage of the recoverable energy in a compression–decompression test. Gels breaking readily via a free-running crack (i.e. high recoverable energy) were perceived as the most crumbly ones. Gels showing slow, yielding-like breakdown (i.e. high energy dissipation) were sensed as the least crumbly by assessors during quantitative descriptive analysis (QDA). Serum release from the gels contributed to a large extent to the energy dissipation and thus decreased crumbliness. Microstructure affects serum release and therefore indirectly microstructure affected the crumbly sensation. The relations between crumbly sensation and physical and structural properties of the gels are, to our knowledge, reported here for the first time and can be applied to control and engineer crumbliness of semi-solid foods. [Copyright &y& Elsevier]

Abstract: The influence of pre-frying and final frying time on the crispness of French fries was evaluated by simultaneous analysis of the fracture and acoustic properties during instrumental simulation of human chewing. The analysis of the frequency distribution of the force and sound events corresponding to the crust of the French fry reflected an effect of both pre-frying and final frying time on instrumental crispness. Up to 60s pre-frying, an increase in the number and magnitude of force and sound events was found, which reflect an increase in crispness. The increase in final frying time increased crispness, but it cannot counterbalance a lack of pre-frying. The moisture content of the whole French fries cannot explained the effect of pre-frying on crispness. Conversely, the effect of pre-frying can be explained when considering only the moisture content of the crust. Pre-frying may allow an easier loss of water from the crust during final frying, which will enhance its crispness. [Copyright &y& Elsevier]

The phase behaviour and mechanical properties of 10 wt% oil-in-water emulsions, stabilised by β-lactoglobulin (β-lg) and flocculated by the polysaccharide dextran were studied as a function of sucrose concentration. The sucrose concentration affected neither the polysaccharide concentration above which depletion flocculation occurred, nor the elastic modulus and maximum linear strain of the emulsion gels formed. Furthermore, only a minor change in size of dextran molecules was measured over the range of sucrose concentrations studied. From this we deduce that the depletion potential between the oil droplets was not significantly affected by addition of sucrose. However, the sucrose concentration did affect the rate of macroscopic phase separation, which could be attributed to a larger viscosity and density of the aqueous phase. Thus, in unheated systems sucrose has a kinetic effect on serum separation in depletion-flocculated emulsions but no significant effect on droplet–droplet interactions. [Copyright &y& Elsevier]

Abstract: The performance of batters containing cellulose derivatives (methyl cellulose (A4M), three hydroxypropylmethyl celluloses (E4M, F4M and K4M) with different degree of hydroxypropyl and/or methyl substitution and carboxymethyl cellulose (CMC)) to produce crispy deep-fried snacks crusts was studied by using a deep-fried crust model. Their performance was compared in terms of their ability to retain moisture content, to decrease oil content and the effect on crispness. Thermogelation properties of the cellulose derivatives depended on the type and degree of substitution. All increased the water content and decreased the oil content of the deep-fried crusts, except for CMC, which does not thermogelate and did not increase the amount of water retained in the crust, although a decrease in the oil content was found. The highest oil reduction and the lowest water retention were found for the cellulose with the lowest level of methyl substitution (K4M). The sound emitted during fracture of K4M crusts had higher intensity than the other cellulose derivatives indicating a crispier crust. [Copyright &y& Elsevier]

Abstract: Consumer appreciation of brittle cellular foods, like bread crusts, depends on textural properties such as crispness. This crispy character is lost above a certain water activity. It is not known what exactly is happening in these crusts when water enters. So is it unclear whether it is the change in the starch or the gluten that initiates the loss of crispness with ageing time. In this paper the effect of water on the glass transition of model bread crusts was studied using two complementary techniques: phase transition analysis (PTA) and temperature modulated differential scanning calorimetry (TMDSC). The mobility of water was studied with nuclear magnetic resonance (NMR). The results were compared with sensory data. Bread crusts prepared with different types of flour were tested to evaluate the effect of flour composition on the crispness of model crusts equilibrated at different relative humidities. In addition the single flour components starch and gluten were studied. Sensory crispness scores decreased with increasing a w from 0.55 upwards. At a w 0.70 sensory crispness was completely lost. Both DSC and PTA showed a transition point at an a w of 0.70–0.75. NMR gave a transition point in the mobility of the protons of water at a w 0.58. This supports the hypothesis that loss of crispness starts as a result of processes at a molecular level, before the macroscopic glass transition. This also suggests that the presence of water that is not directly attached to the solid matrix causes the loss of crispness at low a w. At higher a w increased mobility of the macromolecules will start to play a role. NMR experiments with the separate flour components indicate that the T 2 transition point in starch samples occurs at a lower RH than for gluten. This could imply that starch loses crispness at lower a w than gluten. Increased mobility of small components and side chains might induce increased energy dissipation upon deformation of the material resulting in less available energy for fracture propagation and with that in a less crispy product. [Copyright &y& Elsevier]

Abstract: Bread crust crispness is lost when water migrates from crumb to crust during storage. To what extent water migration is influenced by morphology is not known. Therefore, the effect of crispy rolls morphology on crust crispness was studied. Crispy rolls were prepared at three proving volumes: 300mL (short proving), 500mL (control) and 800mL (long proving). X-ray microtomography was used to characterize morphology. Water transport from crumb to crust was determined. Short proved crispy rolls showed lower rate of crust water uptake while longer proved rolls showed faster uptake during cooling down. Sensory analysis revealed higher crispness for short proved crispy rolls after the same storage time at low RH. We hypothesize that shorter proved crispy rolls with finer crumb morphology, more closed structure, smaller gas cells with less gas cells interconnections and a thicker crust have a significant positive effect on water uptake kinetics and crispness retention. [Copyright &y& Elsevier]

Abstract: A crust model is described that is suited to study crispness of bread crusts as a function of steady state water activity. The study of crispness of this type of products as a function of water activity is complicated since the way a bread crust fractures does not depend on the crust only but also on the properties of the crumb, the curvature of the crust and on the gradient of water activity/content inside the crust. To circumvent these problems a baked crust model was developed. The crust model has similar properties as bread crust in terms of morphology and water adsorption behaviour. The suitability of using the crust model to investigate crispness was validated by studying the effect of water activity on its fracture behaviour and accompanying acoustic emission by using a wedge fracture test. Crispness of the crust model was characterized by a low work of fracture and a high number of sound and force events. When the water activity increased to 0.65 a significant increase of the force required to break the sample was observed, due to moisture toughening. Simultaneously a decrease in the number of force and sound events was found, pointing to a decrease of crispness of the crust model due to water plasticization. [Copyright &y& Elsevier]

Abstract: The effect of air and vacuum cooling on the fracture behaviour and accompanying sound emission, moisture content and crispness of bread crust were investigated. Vacuum cooling resulted in rapid evaporative cooling of products that contained high moisture content. Fracture experiments showed a clear dependence of fracture properties on the way the bread was cooled. Vacuum cooling gave breads with a lower moisture content in the crust than the air cooled breads. Both fracture behaviour and sound emission by bread crust were affected by vacuum cooling. An increase in the number of force and sound events was found which correlated well with the increase in crispness. This treatment also resulted in better retention of crust crispness. Breads stored for 4h at 22°C and 50% RH showed only force and sound events when vacuum was employed. [Copyright &y& Elsevier]

Abstract: Crispness is a salient textural attribute of toasted foods strongly related to their preference. Crispness is affected by water content, mechanical properties and morphology of the food. Sound emission and force characteristics during food crushing play a key role in crispness. The aim was to assess the effect of product morphology on sensory crispness grading of toasted rusk roll, a cellular solid food. Products with coarse and fine structures were studied. Additionally, the effect of water on crispness was studied by using samples with water activities from 0.30 to 0.8. The sensory test showed that upon absorption of water the product became tough and soft and lost its crispness. The morphology of the product had a significant effect on crispness intensity. Coarse products were rated crispier than those with a fine crumb grain. Deterioration of crispness (A w10%) started at 0.46 and 0.50 water activity (6.2% and 7.1% H2O) for the fine and coarse structure product, respectively. The critical water activity (A wc) at which the products lost 50% of the crispness was 0.57 and 0.59 (9.1% and 9.7% H2O), respectively for the fine and coarse structure product. [Copyright &y& Elsevier]