NMR assessment of water uptake in different Vigna spp. seeds

Water uptake in seeds of ten wild and cultivated Vigna spp. accessions was investigated by NMR Spectroscopy. Water absorbed by the intact seeds was measured at intervals by changes in unabsorbed water using analysis of transverse magnetization decay of water protons. Widely different hydration kinetics of first and higher orders were found amongst the samples. the time required to reach saturation hydration capacity ranged from 3 to 16 h; total amount of absorbed water varied from 1.06 to 1.39g H₂O g⁻¹ sample and kinetic constant from 8.2 to 20.4 10⁻³ min⁻¹.
Accessions with a rough seed coat showed a fast water uptake within the first hour while some accessions smooth seed coat need an activation period of 1–5h.
No significant relationships were found between kinetic constant, absorbed water and protein content or some morphological characteristics (100 seed mass, length/width, width/thickness).
Wild species did not absorb water for days, an attribute related to biological survival, but after dehulling they absorbed water at similar rates to the cultivated cowpeas.
NMR can be a suitable technique to investigate some technological characteristics of legumes related to domestic and industrial processing (cooking, canning). It has potential to give data on the various forms of free and bound water, although this was not fully derived in the present work.     

EFFECT OF CARAMELIZATION AND MAILLARD REACTION PRODUCTS ON PEROXIDASE ACTIVITY

Solutions of D-fructose and sucrose were heated, alone and in the presence of glycine. The reaction products were examined in terms of their effects on peroxidase (POD) activity. Compared with glucose mixtures, fructose products had a great inhibiting effect on POD activity, while in the case of Maillard reaction products (MRPs), the differences in antibrowning activity between fructose-glycine and glucose-glycine mixtures were slight. As regards the sucrose and sucrose-glycine solutions, a slight inhibiting effect on POD activity was observed only after sugar hydrolysis. Measurements of the reducing power of sugar and sugar-amino acid solutions showed a correspondence between antioxidant properties of caramelization and Maillard reaction products and their antibrowning effects.     

Use of a Bovine Heme Iron Concentrate in the Fortification of Biscuits

Biscuits were fortified with 4, 6, 8, and 10% heme iron concentrate (HIC). The 10% fortification level presented problems of poor dough quality. The 4, 6, and 8% levels were evaluated for appearance, flavor, texture, taste and aroma and 6% was chosen as the appropriate fortification level. Protein of the fortified biscuit was 1.6 times higher and iron 8 times higher than that of the unfortified control. A shelf life study showed that at 40°C, lipid peroxidation of the biscuits was considerably higher than at room temperature and a catalytic effect of the HIC on the lipid autooxidation was observed. Under controlled conditions, the biscuits could be satisfactorily stored up to 7 months. The fortification of biscuits with HIC represents an interesting alternative for the prevention of iron deficiency.     

Shelf life of ice-stored redfish, Sebastes marinus and S. mentella

Redfish ( Sebastes marinus and S. mentella ) were caught by an Icelandic trawler, stored at about 0°C in boxes in the hold and landed in a German fishing harbour. Boxed redfish, differing in storage time on board, were subsequently stored in melting ice in the chill store of the laboratory at a temperature of +4°C until the borderline of saleability was reached. the quality loss of the ice-stored redfish was monitored by a number of chemical, physical and microbiological parameters including volatile base nitrogen (TVB-N), trimethylamine (TMA), trimethylamine oxide (TMAO), creatine, ethanol, Fishtester readings and number of cfu. AH parameters were correlated with sensory analysis and time in ice.
The rate of deterioration of iced redfish depended on the conditions of storage. Sensory analysis was the most accurate indicator of the limit of saleability of redfish. Iced redfish, stored mainly in a chill store (4–5°C) onshore, had a shelf-life of 16 to 19 days from catching. Fish stored at 0.5°C in the hold of the fishing vessel had a shelf-life of 22 days: These results reflect the different storage temperatures and the effects of handling, transport and storage damage on the quality of the fish. the Fishtester proved to be very useful for the determination of deterioration. Measuring ethanol, TVB-N and TMA gave no information about quality changes during the first 12 days of storage.     

Modifications in Disulfide Reactivity of Milk Induced by Different Pasteurization Conditions

The effect of pasteurization and repasteurization on disulfide chemical reactivity of milk proteins was tested after proteolytic digestion. Pasteurization at 75°C, but not at 80°C or repasteurization, resulted in a decrease in disulfide reactivity compared with raw milk. No differences among heated milks were observed in in vitro protein digestibility, electrophoretic behavior or surface hydrophobicity. Whey proteins extracted from milk pasteurized at 75 and 80° had lower solubility, protein digestibility, disulfide reactivity and surface hydrophobicity than those extracted from raw milks. SDS-PAGE and surface hydrophobicity parameters (K_d, F_max) of whey proteins suggested that differences in disulfide reactivity were a consequence of disulfide-mediated selective aggregation of the whey proteins.     

Electrochemical Regeneration of Activated Carbon Saturated with Toluene

The electrochemical regeneration of an activated carbon, previously saturated with toluene by gas phase adsorption, was studied. Cathodic and anodic regeneration methods were analyzed using a small batch electrochemical cell. In both cases, a stripping efficiency close to 100% was obtained under appropriate conditions of potential, current, and time of electrolysis. Successive loading and regeneration cycles of the activated carbon were performed under cathodic conditions without loss of the adsorption properties of the activated carbon, thus achieving a high regeneration efficiency (close to 99%). This electrochemical method is very effective for regeneration of activated carbon compared to conventional thermal regeneration as it does not modify the porous texture of the material.     

The complex characteristics of crystallization of the Fe75Si15B10 glassy ribbon

The Fe₇₅Si₁₅B₁₀ glassy ribbon was examined in the course of various isothermal and dynamic heat treatments. The number, type and mechanism of formation of the crystallization products formed during two crystallization stages in this alloy were determined by differential scanning calorimetry (DSC), thermomagnetometry, transmission electron microscopy and X-ray diffraction measurements. It is concluded that the first DSC peak is due to the crystallization of α-Fe(Si) or Fe₃Si and the composite microcrystals containing Fe₃B cores with α-Fe(Si) envelopes. The metastable Fe₃B subsequently transforms into the stable Fe₂B in the second DSC peak. The remaining amorphous matrix crystallizes by the eutectic reaction also in the second DSC peak forming the Fe₃Si and Fe₂B eutectic structures. The apparent activation energy E ₁ ^⊛ decreases during the first crystallization stage from 480 kJ (g atom^-1), characteristic of the Johnson–Mehl–Avrami (JMA) nucleation-and-growth kinetics of the as-quenched sample, to 350 kJ (g atom)^-1 implying a dominance of the diffusion-controlled growth of iron in the already pre-nucleated sample. Simultaneously, the JMA exponent n ₁ decreases from 2.5 to 1.5. The apparent activation energy E ₂ ^⊛ depends on the temperature of the first crystallization stage. It decreases with increasing T _a from 384 to 282 kJ (g atom)^-1. This phenomenon was attributed to modification of the chemical composition of the remaining eutectic after the temperature dependent primary crystallization of Fe₃B within the composites. The value of n ₂ is 3. This revised version was published online in November 2006 with corrections to the Cover Date.     

EFFECT OF SUGARS AND MAILLARD REACTION PRODUCTS ON POLYPHENOL OXIDASE AND PEROXIDASE ACTIVITY IN FOOD

The effect of glucose, fructose and sucrose aqueous solutions on polyphenol oxidase (PPO) and peroxidase (POD) activity was studied. Solutions with high concentrations of sugars showed a slight inhibiting effect on PPO while an activation was observed for POD. Glucose solutions, tested after sufficient heat treatments, showed an inhibiting action only on PPO activity. Maillard reaction products, obtained by heating a glucose/glycine solution, caused an unexpectedly strong inhibiting effect on both enzymes. The inhibition became more evident with increasing heating times of the glucose/glycine solution, reducing the activity of PPO and POD nearly to zero. Thus, the Maillard reaction products, already known for their antioxidant properties, were also shown to have a strong inhibiting effect on enzymatic browning.     

Influence of transmembrane pressure on the separation of caprine milk oligosaccharides from protein by cross‐flow ultrafiltration

Goat milk shows similarities with human milk in terms of their oligosaccharides composition. However, the supplementation of goat milk protein in infant formulae is not allowed, which demands a previous separation of oligosaccharides from protein. The purpose of this study was to evaluate the effect of transmembrane pressure on the fractionation of oligosaccharides, protein, lactose and calcium in the diafiltration of caprine milk through a 50 kDa tubular ceramic membrane. Permeates with more than 99% of the original oligosaccharides were obtained after four diavolumes. It was seen that transmembrane pressure had a great influence on filtration time and protein transmission.