Thermal processing implications on the digestibility of meat,fish and seafood proteins

Thermal processing is an inevitable part of the processing and preparation of meat and meat products for human consumption. However, thermal processing techniques, both commercial and domestic, induce modifications in muscle proteins which can have implications for their digestibility. The nutritive value of muscle proteins is closely related to their digestibility in the gastrointestinal tract and is determined by the end products that it presents in the assimilable form (amino acids and small peptides) for the absorption. The present review examines how different thermal processing techniques, such as sous-vide, microwave, stewing, roasting, boiling, frying, grilling, and steam cooking, affect the digestibility of muscle proteins in the gastrointestinal tract. By altering the functional and structural properties of muscle proteins, thermal processing has the potential to influence the digestibility negatively or positively, depending on the processing conditions. Thermal processes such as sous-vide can induce favourable changes, such as partial unfolding or exposure of cleavage sites, in muscle proteins and improve their digestibility whereas processes such as stewing and roasting can induce unfavourable changes, such as protein aggregation, severe oxidation, cross linking or increased disulfide (S-S) content and decrease the susceptibility of proteins during gastrointestinal digestion. The review examines how the underlying mechanisms of different processing conditions can be translated into higher or lower protein digestibility in detail. This review expands the current understanding of muscle protein digestion and generates knowledge that will be indispensable for optimizing the digestibility of thermally processed muscle foods for maximum nutritional benefits and optimal meal planning.     

Prediction, analysis and solution of the flow inversion phenomenon in a typical MTR-reactor with upward core cooling

Research reactors of power greater than 20 MW are usually designed to be cooled with upward coolant flow direction inside the reactor core. This is mainly to prevent flow inversion problems following a pump coast down. However, in some designs and under certain operating conditions, flow inversion phenomenon is predicted. In the present work, the best-estimate Material Testing Reactors Thermal-Hydraulic Analysis program (MTRTHA) is used to simulate a typical MTR reactor behavior with upward cooling. The MTRTHA model consists of five interactively coupled submodels for: (a) coolant, (b) fuel plate, (c) chimney, lower plenum, suction box and cold leg, (d) flap valve and (e) natural circulation flow. The model divides the active core into a specified axial regions and the fuel plate into a specified radial zones, then a nodal calculation is performed for both average and hot channels with a chopped cosine shaped heat generation flux. The reactor simulation under loss of off-site power is performed for two cases namely: two-flap valves open and one flap-valve fails to open. The simulation is performed under a hypothetical case of loss of off-site power. Unfortunately, the flow inversion phenomenon is predicted under certain decay heat and/or pool temperature values below the design values. In most cases, the flow inversion phenomenon is accompanied by boiling which is undesirable phenomenon in this type of reactors as it could affect the fuel-clad integrity. The model results for the flow inversion phenomenon prediction are analyzed and a solution of the problem is suggested.     

Geostatistical mapping of precipitation: implications for rain gauge network design.

This study examined four univariate kriging techniques; simple kriging (SK), ordinary kriging (OK), multi-Gaussian kriging (MGC), and log-normal kriging (LNK); and two multivariate kriging algorithms; kriging with external drift (KED) using elevation and slope in two different models for the estimation of daily rainfall in a 250 m x 250 m grid over a 750 km2 area in the Canadian Boreal forest. Multivariate kriging did not enhance daily rainfall predictions. SK, OK, and LNK produced statistically comparative results with OK being slightly better. MGC was the worst univariate estimator, mainly due to the high percentage of data spikes. Sequential Gaussian simulation (SGS) was then implemented to produce 100 equiprobable maps of rainfall. A multi-objective approach; that is based on overlaying the map of the kriging variance, the DEM, and land use/land cover maps in a GIS framework to identify the areas of commonly favourable features; was proposed to identify potential future sampling locations.     

Synthesis and properties of amphoteric surfactants

Carboxylic amphoteric surfactants containing ether tertiary amino and carboxylic groups were prepared. Specifically, 2-(2-dimethyl-aminoethoxy)octadecanoic, hexadecanoic and dodecanoic acid hydrochloride were synthesized. Surface and interfacial tension, emulsifying action, corrosion inhibition effect and after-treatment of direct dyed cotton fabrics were determined for these surfactants. Antibacterial activities were also examined. Chem. Eng. Dept., Faculty of Engineering.     

Degradation of cyanobacteria toxin by advanced oxidation processes

Advanced oxidation processes (AOPs) using O(3), H(2)O(2), O(3)/H(2)O(2), O(3)/Fe(II), and Fenton treatment were investigated for the degradation of aqueous solutions of cyanobacteria. The effects of concentration of reactants, temperature, and pH on toxins degradation were monitored and the reaction kinetics was assessed. O(3) alone or combined with either H(2)O(2) or Fe(II) were efficient treatment for toxins elimination. A higher toxin oxidation tendency was observed with Fenton reaction; total toxins degradation (MC-LR and MC-RR) was achieved in only 60s. The ozonation treatment was successfully described by second-order kinetics model, with a first-order with respect to the concentration of either ozone or toxin. At 20 degrees C, with initial concentration of MC-LR of 1mg/L, the overall second-order reaction rate constant ranged from 6.79 x 10(4) to 3.49 x 10(3)M(-1)s(-1) as the solution pH increased from 2 to 11. The reaction kinetics of the other AOPs (O(3)/H(2)O(2), O(3)/Fe(II), and Fenton), were fitted to pseudo first-order kinetics. A rapid reaction was observed to took place at higher initial concentrations of O(3), H(2)O(2) and Fe(II), and higher temperatures. At pH 3, initial concentration of toxin of 1mg/L, the pseudo first-order rate constant, achieved by Fenton process, was in order of 8.76+/-0.7s(-1).     

A high-order curvature compensation technique for bandgap voltage reference using subthreshold MOSFETs

A bandgap voltage reference with high-order curvature compensation is presented in this study. It exploits subtraction and derivative equalisation of currents generated from two complementary NMOS and PMOS bandgap references (BGRs) using subthreshold MOSFETs. By equating the derivative with respect to temperature of the two currents, generated by the complementary bandgaps, and subtracting these currents, an accurate high-order curvature compensation is achieved. To overcome problems due to the limited input common-mode range of opamps used in BGRs, a transimpedance amplifier with new accurate current compensation that tracks the temperature variation is proposed. This bandgap is implemented using the 0.18 μm CMOS process with a supply voltage as low as 0.7 V. At 0.8 V power supply and an output reference voltage of 386 mV, the proposed circuit achieves a temperature coefficient of 19 ppm/°C from 0 to 130°C. The power consumption is 119 μW and the power supply reduction ratio is 24 dB at 1 kHz.     

Synthesis of polyalkylacrylate nanolatexes by microemulsion polymerization method

The paper concerns with the radical polymerization of [octadecyl acrylate (ODA), isooctyl acrylate (iso-OA) and α-olefins 1-Octene (n-O)]. These microemulsions were stabilized by sodium dodecyl sulfate (SDS) and initiated by water-soluble initiator potassium persulfate (KPS). The nanolatex particle sizes were determined by transmission electron microscope (TEM). They were situated between 10 and 100 nm. The microstructures were confirmed by FT-IR and molecular weights determined by Gel permeation chromatography (GPC). The obtained M. wt. were (≈70 × 10³, 101 × 10³ and 153 × 10³ g/mol). The polydispersity, molecular weights, and particle sizes were discussed in the light of micelle formation and shape of the alkyl group via emulsion polymerization.     

Physical Interventions to Manipulate Texture and Tenderness of Fresh Meat: A Review

Meat tenderness is a major eating quality attribute that ensures consumer satisfaction and repeat purchase of red meat. The variability in meat tenderness is related to several factors that are spread across the production chain (biological, on farm, processing, and consumer factors), which can lead to inconsistent tenderness in fresh red meat products. The tenderization process is dictated by physical and biochemical factors, which appear to affect the proteases involved in protein degradation and, consequently, they regulate the rate and extend of tenderization in meat. Several physical, chemical, and biochemical interventions have been investigated to improve the tenderness of meat. The present review discusses the physical interventions used to manipulate the texture of meat and their mechanism of action, optimal tenderizing conditions, and their effects on other meat quality attributes (colour stability, lipid oxidation, and water holding capacity). Attention should be paid to other quality attributes for full evaluation of the differing interventions.     

Impact of peroxydisulfate in the presence of zero valent iron on the oxidation of cyclohexanoic Acid and naphthenic acids from oil sands process-affected water

Large volumes of oil sands process-affected water (OSPW) are produced during the extraction of bitumen from oil sands in Alberta, Canada. The degradation of a model naphthenic acid, cyclohexanoic acid (CHA), and real naphthenic acids (NAs) from OSPW were investigated in the presence of peroxydisulfate (S(2)O(8)(2-)) and zerovalent iron (ZVI). For the model compound CHA (50 mg/L), in the presence of ZVI and 500 mg/L S(2)O(8)(2-), the concentration decreased by 45% after 6 days of treatment at 20 °C, whereas at 40, 60, and 80 °C the concentration decreased by 20, 45 and 90%, respectively, after 2 h of treatment. The formation of chloro-CHA was observed during ZVI/S(2)O(8)(2-) treatment of CHA in the presence of chloride. For OSPW NAs, in the presence of ZVI alone, a 50% removal of NAs was observed after 6 days of exposure at 20 °C. The addition of 100 mg/L S(2)O(8)(2-) to the solution increased the removal of OSPW NAs from 50 to 90%. In absence of ZVI, a complete NAs removal from OSPW was observed in presence of 2000 mg/L S(2)O(8)(2-) at 80 °C. The addition of ZVI increased the efficiency of NAs oxidation by S(2)O(8)(2-) near room temperature. Thus, ZVI/S(2)O(8)(2-) process was found to be a viable option for accelerating the degradation of NAs present in OSPW.     

The use of natural herbal extracts for improving the lipid stability and sensory characteristics of irradiated ground beef

Ground Longissimus dorsi of beef were treated with herbal extracts of marjoram, rosemary and sage at concentration of 0.04% (v/w), radiation (2 or 4.5 kGy) or their combination. Treated samples were stored at 5 °C and analyzed periodically for thiobarbituric acid reactive substances (TBARS), sensory characteristics and psychrotrophic bacterial counts during storage for 41 and 48 days for samples treated at 2 and 4.5 kGy respectively. Results demonstrated a significant benefit of the addition of herbal extracts to the ground beef prior to irradiation. All three extracts significantly (P < 0.05) lowered the TBARS values and off-odor scores and significantly (P < 0.05) increased color and acceptability scores in all samples with marjoram being the most effective. The combination treatment with herbal extracts plus irradiation resulted in extension of the shelf life of samples treated with 2 kGy by one week and samples treated with 4.5 kGy by two weeks, over that treated with irradiation alone. In conclusion, the addition of herbal extracts can minimize lipid oxidation, improve color and decrease off-odor production in irradiated ground beef.