Graft copolymerization of acrylonitrile onto bagasse and wood pulps

Graft copolymerization of acrylonitrile onto bagasse and wood pulps has been studied using ceric ammonium nitrate as initiator. The effect of order of reactants addition on grafting was examined: three methods were studied. Addition of the pulp to a mixture of initiator and monomer (method A) resulted in more efficient grafting than the other two methods. The reaction produced more grafting at 50°C than at 30°C or at 40°C. The results showed that the monomer and initiator concentrations are the major factors influencing the grafting rate of acrylonitrile. Increasing the acrylonitrile or initiator concentration was accompanied by a substantial increase in graft yields. Increasing the initiator concentration is more effective on polymerization rate than the increase in monomer concentration. The extent of grafting of this monomer can best be controlled by reaction time. Water swelling of pulps significantly affected the grafting rate of acrylonitrile as well as the ceric consumption during grafting. The reactivity of bagasse pulp towards grafting of acrylonitrile is higher than that of wood pulp due to a more open structure of cellulose in bagasse pulp as well as the presence of some lignin which accelerates grafting. Ceric consumption during grafting depends on the nature of the pulp as well as the monomer and initiator concentrations, time, temperature, and the method of grafting. More Ce(IV) is consumed during grafting than during oxidation of the pulps under identical reaction conditions, due to homopolymer formation which accompanied grafting. The ceric consumption by bagasse during grafting or oxidation is somewhat greater than that consumed by wood pulp under similar reaction conditions.     

Filtration in hydrophobic media: 2. A triglyceride partition phenomenon as observed by tangential filtration of butter oil

Having demonstrated a partition of a hydrophobic medium (butter oil) under crossflow filtration and having tentatively explained the phenomenon on stereochemical and saturation basis, the molecular partition was studied by tangential filtration. Under specific hydrodynamic conditions, a filtration phenomenon was demonstrated. The solid fat content (SFC) at 20°C of the fractions obtained was investigated accordingly. When the molecular partition takes place, an SFC divergency between the permeate and the retentate is observed. The amplitude of the divergency depends on experimental conditions.     

Ultrastructure of low-fat ground beef patties with added whey protein concentrate

Microstructure of gels formed at 71°C from different mixtures of beef myofibril protein (BMP; 6.1% protein) and whey protein (WP) were studied by transmission electron microscopy (TEM). At a ratio of30:10 (w/w) of whey protein concentrate (WPC; 79.5% protein) to BMP, WP formed a network of aggregated clusters in which beef myofibril proteins were embedded. WP apparently acts as a filler and possibly as a cementing agent for the meat pieces. At a lower ratio of 10:30 (wl w), the WP aggregates occupied and increased the interstitial spaces between the myofibril protein and reinforced the network. The location of WP in the interstitial spaces might explain its water binding ability in beef patties formulated with WP and water. WP protected the beef myofibril protein structure during heating as less disintegration in the Z-line was observed in gels with WP compared to the control. Low-fat (10% fat) ground beef patties with added 10% water and 1–4% whey protein concentrate (WPC), cooked to three different internal temperatures (60, 70 and 80°C), were evaluated for their cooking characteristics and examined by TEM. For all levels of addition, WPC improved the cooking yield compared to a non-formulated control of 10% fat. Fat retention was also improved at the highest level of WPC addition. The increased cooking yield was shown to be caused principally by the better water retention. The textural parameters, hardness and chewiness, were not affected by WPC addition but increased with increasing cooking temperature. These temperature-induced changes were matched by marked changes to the ultrastructure of the meat products.     

Crystallization behaviour and hardness of glass ceramics rich in nanocrystals of ZrO2

This research is mainly directed toward the development of hardness of glass ceramic by adding different amounts of ZrO₂ to the glass and by applying different heat-treatments. Differential thermal analysis (DTA), X-ray diffraction (XRD) and Scanning electron microscope (SEM) were used to study the crystallization behaviour of the glass samples. The only observed crystalline phases were tetragonal and monoclinic zirconia. Hardness was found to increase by increasing time and temperature of heat-treatment due to the formation of monoclinic phase as a result of the martensitic reaction. This transformation opposes crack opening.     

Characterization of semipurified enterocins produced by Enterococcus faecium strains isolated from raw camel milk

Food safety has become an issue of great interest worldwide. Listeria monocytogenes is a food-borne pathogen that causes listeriosis and is difficult to control in the dairy industry. The use of lactic acid bacteria (LAB) and their antimicrobial substances against Listeria is promising in food applications. Here, we report the isolation from raw camel milk of LAB displaying antilisterial activity. Two isolates were selected for their secretion of bacteriocin(s) and identified by 16S rRNA sequencing as Enterococcus faecium S6 and R9. The produced bacteriocins were partially purified by ammonium sulfate precipitation and then biochemically characterized. Antimicrobial activity was estimated to be 6,400 and 400 AU (arbitrary units)/mL for E. faecium S6 and R9, respectively. The proteinaceous nature of the bacteriocins was confirmed via enzymatic reactions. Moreover, lipolytic and glycolytic enzymes completely inactivated the antimicrobial effect of the bacteriocins. These bacteriocins were heat-resistant and stable over a wide range of pH (2.0 to 10.0). To confirm its inactivation by lipolytic and glycolytic enzymes, the bacteriocin of E. faecium S6 was further purified by gel filtration, which suggested the existence of carbohydrate and lipid moieties. In addition, enterocin-coding genes were identified by PCR, showing DNA fragments corresponding in size to enterocins A, B, and P for E. faecium S6 and to enterocins B and P for E. faecium R9. In conclusion, these results indicate that partially purified bacteriocins from E. faecium S6 and R9 may be beneficial in controlling Listeria in the dairy industry.     

Effect of La2O3, CoO,Cr2O3 and MoO3 nucleating agents on crystallization behavior and magnetic properties of ferromagnetic glass–ceramic in the system Fe2O3·CaO·ZnO·SiO2

Preparation and characterization of ferromagnetic glass ceramic in the system Fe₂O₃·CaO·ZnO·SiO₂ with different nucleating agents was studied. The effect of La₂O₃, CoO, Cr₂O₃ and MoO₃ as nucleating agents was investigated. Differential thermal analysis; X-ray diffraction and transmission electron microscope were used to investigate thermal behavior, sequence of crystallization and microstructure of the samples. XRD analysis for as prepared samples revealed the crystallization of single magnetite phase. Heat treatment at 900 °C/2 h revealed the appearance of minor amounts of calcium silicate, hematite and cristobalite beside magnetite. TEM revealed crystallization of crystallite size in the range 50–100 nm. Lattice parameters, cell volume and crystallite size were stimulated from XRD data. Magnetic properties of quenched samples were measured under 20 kG.     

Flow injection potentiometric determination of Chlorphenoxamine Hydrochloride

New Chlorphenoxamine (Ch) ion selective plastic membrane electrodes for both conventional and coated wire types based on the ion associate of Ch-HCl with sodium tetraphenylborate (NaTPB) and phosphotungestic acid (PTA) were prepared. The conventional type electrode was fully characterized in terms of membrane composition, plasticizer, filling solution, life span, pH, ionic strength, temperature. The membranes of optimum compositions were used for the preparation of both graphite and cupper coated wire electrodes. The prepared electrodes were used for the potentiometric determination of the investigated drug in raw material and pharmaceutical preparations under batch and flow injection analysis conditions. The selectivity of the electrodes towards a large number of excipients like inorganic cations, sugars, amino acids and other antihistaminic drugs was tested. Determination of Ch-HCl, the solubility product of the ion associate and the formation constant of the precipitation reaction leading to the ion associate formation of Ch-HCl with NaTPB and PTA were carried out using conductimetric measurements.     

Numerical study of momentum and heat transfer in a pulsed plane laminar jet

In this paper, we propose numerical solutions for a two-dimensional pulsed plane jet in unsteady laminar regime. At the exit of the nozzle, the pulsating flow is imposed with a uniform temperature T₀ and a velocity u=u₀(1+Asin(ωt)). Two cases are considered: the free and the wall pulsed plane jet. For the wall jet case, the wall may either be considered adiabatic or subjected to a uniform temperature. Equations are treated with an appropriate finite difference method. The effect of the important governing parameters, such as the amplitude and the frequency of the pulsation, the Reynolds and Grashof numbers on the flow behavior are also investigated in detail. The results obtained show that the pulsation affects the flow in a vicinity region of the nozzle to reach the same asymptotic regime than the steady jet. The results also indicate that the initial development of the jet is considerably accelerated and the entrainment in the first diameters is enhanced.