Physico-chemical properties of whey protein isolate films containing oregano oil and their antimicrobial action against spoilage flora of fresh beef

Antimicrobial films were prepared by incorporating different levels of oregano oil (0.5%, 1.0%, and 1.5% w/w in the film forming solution) into sorbitol-plasticized whey protein isolate (WPI) films. The moisture uptake behavior and the water vapor permeability (WVP) were not affected by the addition of oregano oil at any of the concentrations used. A reduction of the glass transition temperature (∼10–20 °C), as determined by dynamic mechanical thermal analysis (DMTA), was caused by addition of oil into the protein matrix. A decrease of Young modulus (E) and maximum tensile strength (σ_max) accompanied with an increase in elongation at break (%EB) was observed with increasing oil concentration up to a level of 1.0% (w/w). Wrapping of beef cuts with the antimicrobial films resulted in smaller changes in total color difference (ΔΕ) and saturation difference (Δ_chroma) during refrigeration (5 °C, 12 days). The maximum specific growth rate (μ_max) of total flora (total viable count, TVC) and pseudomonads were significantly reduced (P < 0.05) by a factor of two with the use of antimicrobial films (1.5% w/w oil in the film forming solution), while the growth of lactic acid bacteria was completely inhibited. These results pointed to the effectiveness of oregano oil containing whey protein films to increase the shelf life of fresh beef.     

A study of steam methanol reforming in a microreactor

Steam reforming of methanol is investigated numerically considering both heat and mass transfer of the species in a packed bed microreactor. The numerical results are shown to be in good agreement with experimental data [M.T. Lee, R. Greif, C.P. Grigoropoulos, H.G. Park, F.K. Hsu, J. Power Sources Transport in, 166 (2007) 194–201] with a BASF F3-01(CuO/ZnO/Al₂O₃) catalyst. A correlation for the conversion efficiency of methanol has been obtained as a function of the operating temperature and a dimensionless time parameter which represents the ratio of the characteristic time of the methanol flow to the time for chemical reaction. The results show that for the constant wall temperature condition the steam reforming process of methanol results in a nearly uniform temperature throughout the microreactor over the range of operating conditions.     

Experimental study on spreading and evaporation of inkjet printed pico-liter droplet on a heated substrate

In this work, the spreading and evaporation of 2–70 pL droplet (17–50 μm diameter) of water and ethylene glycol jetted by drop-on-demand piezo-driven jetting head on the heated substrate are studied. According to the experimental results, the interfacial oscillation phenomena of water droplet whose Ohnesorge number (Oh) is about 10^?2 is similar to that in inviscid impact driven region, while that of ethylene glycol droplet (Oh ≈10^?1) is similar to that in highly viscous impact driven region followed by capillary driven extra spreading. In addition, various time scales used for nano/micro-liter droplets agree well with the times for interfacial oscillation, viscous damping, extra wetting, and evaporation in pico-liter droplets. In the case of water droplet, the spreading processes end before the evaporation becomes significant. However, in the case of highly viscous ethylene glycol droplet, the extra wetting overlaps the evaporation at high temperature.     

Effects of the excluded volume interactions on the conformational properties of star polymers

The effects of the excluded volume interactions on the conformational properties of star polymers have been studied. First order calculations at the critical dimensionality d = 4 yield the critical exponents of the average quantities up to first order in ε = 4-d. We thus find the partition function, the probability of the end of a branch to reach the central core and the probability of contact of the ends of two branches. The size of the macromolecule, expressed by the mean square radius of gyration 〈s²〉_star is studied in the region where the interactions between the polymeric units repel one another and in the region where the units attract one another. The results are compared with the results of previous works and with experiments.     

Amphiphilic diblock and ABC triblock methacrylate copolymers: synthesis and aqueous solution characterization

Three isomeric, linear, equimolar, amphiphilic ABC triblock copolymers comprising methyl methacrylate (MMA, nonionic hydrophobic), 2-(dimethylamino)ethyl methacrylate, (DMAEMA, ionizable hydrophilic) and hexa(ethylene glycol) methacrylate (HEGMA, nonionic hydrophilic) units (10 units in each block) were synthesized by group transfer polymerization (GTP). These were the three block sequence isomers, ABC, ACB and BAC. The corresponding random terpolymer was also prepared. The molecular weights and compositions of all the polymers were characterized by GPC and ¹H NMR. Measurements of the hydrodynamic diameters and cloud points of the copolymers in aqueous solution suggest that the various distributions of monomer units in the four terpolymers (the three triblocks and the random) result in different supramolecular structures with different colloidal stabilities.