Calculation of thermal protein changes in food with heat conduction. Determination of reaction rate and activation heat]

The velocity constant k of protein changes is commonly determined by heating as abruptly as possible to a given temperature for various periods. Its dependence on temperature or activation heat is deduced from the k value determinations at different temperatures, using the ARRHENIUS diagram. In contrast to this, the authors determined the k and E values in a temperature field for a constant reaction time. This is done directly in the foodstuff which is introduced (in ball form) into a bath of constant temperature. In case of foodstuffs with mere heat conduction, there are in the interior innumerable spherical shells subjected to the same thermal stress which increases from within towards the exterior. Thermal protein changes (such as the thermal coagulation of egg white and muscle proteins and the formation of metmyochromogen) which can be visualized directly or, in case of enzymatic denaturation, indirectly by colour reactions, using the presence-absence method, may be observed if the ball is cut in half. This procedure (termed "change-over method" by the authors) permits to calculate the unknown k and E values from the radius of the visible inner circle. (This applied also to cylindrical forms.) Since this method allows to estimate approximately these reaction kinetic constants directly in the foodstuff under conditions encountered in practice, it is in many cases better suited for simulating, calculating, or optimizing desirable or undesirable protein changes occurring during thermal processing than the mere model experiment with abrupt heating which does not reproduce the changes in the reaction medium occuring during the slow increase or decrease in temperature.     

Heavy metals and trace elements levels in milk and milk products

Milk and dairy products are an important food in the human diet. The present investigation was carried out to determine concentrations of lead, cadmium, zinc, copper and iron in milk and dairy products and evaluate the potential health risks of metals to humans via consumption of milk and dairy products. A total of 77 samples of milk and dairy products (22 raw milk, 20 kareish cheese, 21 butter and 14 rice pudding) were collected from farms, individual farmers and dairy shops in Beni-Suef governorate, Egypt. Pb, Cd, Zn, Cu and Fe concentrations in milk and dairy products ranged from 0.044–0.751, 0.008–0.179, 0.888–18.316, 0.002–1.692 and 1.3208–45.6198 ppm respectively. Pb concentration in all samples exceeded the maximum permissible limit (0.02 mg/kg) established by codex standard. Pd and Cd intake through milk and dairy products consumption were 1.27 and 0.33 μg/kg bw/day, which represent 35.3 and 39.8 % of the tolerable daily intake. Dairy products are poor sources of iron, copper and zinc, and milk contributes little to the total iron and zinc intake. Target hazard quotient values of less than 1 indicate a relative absence of health risks associated with the consumption of milk and dairy products.     

Network coding for MPR-based flooding in ad hoc wireless networks under mobility conditions

We propose a novel distributed coding scheme for broadcast over mobile ad hoc networks. In this scheme, we combine MPR technique with network coding. Only multipoint relay (MPR) nodes perform coding using a rateless code. Rather than waiting for a large number of encoded packets to be received before MPR nodes could decode and resend coded packets, we design a new degree distribution that enables the nodes to start decoding even when small number of encoded packets are received. Thus, we decrease the delay introduced at the intermediate nodes. The main advantage of using a rateless code for encoding instead of using a random linear combination of the previously received packets is to reduce significantly the encoding and decoding complexities. We provide a performance evaluation using a simulation to demonstrate the efficiency of our code even under mobility condition.     

Studies on Wheat Steep Liquor Produced During Starch Production

Chemical analysis of wheat steeping liquor, produced from soaking of wheat grains revealed the presence of 1% total soluble solids with 7,15% proteins. A method was devised to obtain large amounts of precipitates with protein content up to 9,84%. Glutamic acid and lysine constitute the largest proportions of the amino acids. Nine essential amino acids were found. The raw wheat steeping liquor and the supernatant resulting after separation of the protein were used as a growth medium for the production of fodder yeast Candida tropicalis.     

Condensation of Unsaturated SCHIFF Bases with ethyl acetoacetate,diethyl malonate and acetylacetone

1, 4-Dihydropyridine derivatives have been obtained by MICHAEL condensation with cinnamylidene anilines 1 or N-p-tolyl-chalcone imine 5 . With ethyl acetoacetate 1 and 5 yield 1-aryl-2-methyl-3-ethoxycarbonyl-4-phenyl-1, 4-dihydropyridines 2 and 6 , with diethyl malonate 1-aryl-3-ethoxycarbonyl-2-oxo-4-phenyl-1, 2, 3, 4-tetrahydropyridines 7 and 8 , and with acetyl acetone 1-aryl-2-methyl-3-acetyl-4-phenyl-1, 4-dihydropyridines 9 and 10 .     

Simplified seismic life cycle cost estimation of a steel jacket offshore platform structure

The purpose of the present paper is to develop a simple methodology for seismic life cycle cost (LCC) estimation for a steel jacket offshore platform structure. This methodology accounts for accuracy of LCC modelling as well as simplicity of application. Accuracy is maintained through incorporating the effect of aleatory and epistemic uncertainties in the LCC estimation framework. Simplicity is achieved by using equivalent single-degree-of-freedom (ESDOF) system instead of the full structure and by eliminating full incremental dynamic analysis and fragility analysis. Instead, an approximate fragility curve and a localised incremental dynamic analysis curve are used along with a probabilistic simple closed-form solution for loss estimation. In the design of model structures, different bracing systems are used for the seismic design of the offshore platform, such as conventional and buckling-restrained braces. The proposed LCC methodology is validated through comparison with the results from a more rigorous method. It is found that even though the proposed methodology results in a slightly different solution compared to the reference method, the method can be used as an efficient tool for preliminary LCC evaluation of structures.     

Miscibility and the specific interaction of polyhydroxybutyrate blended with polyvinylacetate and poly(vinyl acetate‐co‐vinyl alcohol) with some biological applications

Bacterially produced polyhydroxybutyrate (PHB) polymer has a lot of potential as an application for environmentally degradable plastics. We aimed in this study to blend PHB with the semicrystalline polymers poly(vinyl acetate) (PVAc) and poly(vinyl acetate‐co‐vinyl alcohol) (PACA) to obtain material with better physical properties. We investigated compatibility over a wide composition range using different techniques. Viscosity measurements were used to study polymer–polymer miscibility in dilute solutions with chloroform as cosolvent. The data is discussed according to the viscosity interaction parameters, which are treated as excess properties by similarity with those of real solutions. Dielectric investigations were carried out at different frequencies ranging from 100 Hz to 50 kHz. The obtained data indicated that more than one relaxation mechanism was present, which were ascribed to the rotation of the main chain and its related motions. A glass‐transition temperature composition diagram, IR spectroscopy, and a morphological investigation were also used to give more information about the compatibility of such blends. The results of this study indicate that PHB/PVAc is semicompatible, whereas PHB/PACA is compatible at least in the assayed composition range of hydrolysis. We also extended the study to carry out some biological activity investigations, which were tested against the representative number of pathogenic organisms with the disk diffusion method. The different compositions of the investigated blend were biologically active when compared with the individual polymers. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 86: 2363–2374, 2002     

Some color aspects of Parian bodies

The two coloring oxides, CoO and NiO were included separately in a self-glazed parian body ?highly feldspathic porcelain? in 5 different concentration between 1 and 10 wt%. The host body consisted of 75% feldspar and 25% kaolin. The mixes were pressed and matured between 1125°C and 1150°C. The produced colors were characterized visually as well as in reference to the CIE system. The densification of the blue and green bodies were slightly reduced, although higher density values were achieved. This was attributed to the effect of the Co²⁺ or Ni²⁺ dense aluminate or silicate. However, their influence was counter balanced by the enhanced leucite formation and higher porosity glassy phase. Various shades of blue were obtained by introducing Co²⁺. Maximum difference in color Δ E = 12.97 Judds was obtained by incorporating 5 wt % and firing at 1125°C while a value of 11.69 Judds was obtained upon firing a specimen with only 1 wt % at 1150°C. The latter value is comparable to that obtained by incorporating 10% of blue stain. Ni²⁺ produced various shades of green with a maximum of Δ E = 5.44 Judds upon firing a sample with 5 wt % at 1150°C. The results are discussed in view of the ligand field theory as well as X-ray diffraction analysis.