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.     

Detection of Schistosoma mansoni and Schistosoma haematobium by Real-Time PCR with High Resolution Melting Analysis

The present study describes a real-time PCR approach with high resolution melting-curve (HRM) assay developed for the detection and differentiation of Schistosoma mansoni and S. haematobium in fecal and urine samples collected from rural Yemen. The samples were screened by microscopy and PCR for the Schistosoma species infection. A pair of degenerate primers were designed targeting partial regions in the cytochrome oxidase subunit I (cox1) gene of S. mansoni and S. haematobium using real-time PCR-HRM assay. The overall prevalence of schistosomiasis was 31.8%; 23.8% of the participants were infected with S. haematobium and 9.3% were infected with S. mansoni. With regards to the intensity of infections, 22.1% and 77.9% of S. haematobium infections were of heavy and light intensities, respectively. Likewise, 8.1%, 40.5% and 51.4% of S. mansoni infections were of heavy, moderate and light intensities, respectively. The melting points were distinctive for S. mansoni and S. haematobium, categorized by peaks of 76.49 ± 0.25 °C and 75.43 ± 0.26 °C, respectively. HRM analysis showed high detection capability through the amplification of Schistosoma DNA with as low as 0.0001 ng/µL. Significant negative correlations were reported between the real-time PCR-HRM cycle threshold (Ct) values and microscopic egg counts for both S. mansoni in stool and S. haematobium in urine (p < 0.01). In conclusion, this closed-tube HRM protocol provides a potentially powerful screening molecular tool for the detection of S. mansoni and S. haematobium. It is a simple, rapid, accurate, and cost-effective method. Hence, this method is a good alternative approach to probe-based PCR assays.     

Pyrazole Derived Cationic Surfactants and their Tin and Copper Complexes: Synthesis,Surface Activity,Antibacterial and Antifungal Efficacy

Five membered heterocyclic cationic 3-pyrazolium surfactants namely: 2-[2-(alkyloxy)-2-oxoethyl]-3-methyl-5-oxo-1-phenyl-4,5-dihydro-1H-3-pyrazolium bromide (decyl-; dodecyl-) and their copper and tin complexes were synthesized, their structures were confirmed using different spectroscopic tools. The IR spectra of the metal complexes showed that these compounds exhibit a tetrahedron structure with the transition metal ion (M²⁺) at the center and the cationic ligands arranged in the apexes, while the halide ions in the center. The synthesized compounds were evaluated as biocides against different types of bacteria and fungi. The biological activity data showed that the cationic surfactants exhibit moderate to high efficacy against the tested microorganisms (either bacteria or fungi). While, complexation of these cationic surfactants with Cu (II) and Sn (II) ions the antimicrobial activity was strongly increased. The surface activity of these compounds were discussed and correlated to their chemical structure and the type of substituents on the heterocyclic moiety. Meanwhile, the antimicrobial assay was correlated to the surface activities of the synthesized compounds.     

Energy and exergy analysis of a new solar air heater with latent storage energy

In this paper, we propose a new solar air heater with a packed-bed latent storage energy system using PCM spherical capsules. At daytime, the solar heating system stored the thermal solar energy as sensible and latent heat, however, at night it restored. Some parameters, such as the global solar radiation and the mass flow rate are varied to investigate their effect on the absorbed, used, and recovered heat from the system. An optimization study using the first and second laws of thermodynamics is also carried out to obtain the energy and exergy efficiencies. The experimental study was conducted, designed, and realized in the Research and Technology Center of Energy (CRTEn) in Tunisia. The experimentally obtained results are used to analyze the performance of the system, based on temperature distribution in different parts of the collectors, absorbed, instantaneous stored and used thermal energy. The daily energy efficiency varied between 32% and 45%. While the daily exergy efficiency varied between 13% and 25%. The effect of the mass flow rate of air on the outlet temperature of the solar air heater is examined.     

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.