Survival of Staphylococcus aureus and Listeria monocytogenes on vacuum-packaged beef jerky and related products stored at 21 degrees C

In the manufacture of beef jerky, a thermal lethality step is followed by drying to prevent growth of pathogenic bacterial postprocessing contaminants on the finished product. Recent guidelines from the U.S. Department of Agriculture have raised the question of the maximum water activity (a(w)) in jerky products that will inhibit growth of pathogenic bacteria. The survival of the potential postprocessing contaminants Staphylococcus aureus and Listeria monocytogenes was evaluated on 15 vacuum-packaged beef jerky and related products with a(w) values ranging from 0.47 to 0.87, just below the 0.88 limit reported for anaerobic growth of S. aureus. Small individual product pieces were inoculated on the outer surface with five strains each of S. aureus and L. monocytogenes, repackaged under vacuum, and stored at room temperature (21 degrees C) for 4 weeks. Pathogen numbers were determined before storage and after 1 and 4 weeks. None of the 15 jerky products supported growth of either pathogen. Counts of S. aureus fell by 0.2 to 1.8 log CFU after 1 week of storage and by 0.6 to 5.3 log CFU after 4 weeks of storage. Numbers of L. monocytogenes fell by 0.6 to 4.7 log CFU and by 2.3 to 5.6 log CFU after 1 and 4 weeks of storage, respectively. Although factors other than a(w) may have some effect on pathogen survival, the results of the present study clearly support drying beef jerky to an a(w) of < or = 0.87 to ensure that bacterial pathogens cannot grow on vacuum-packaged product stored at room temperature.     

Preparation and microwave characterization of PTFE/PEEK blends

Present paper describes the preparation and characterization of the PTFE / PEEK blends. The surface morphology of different volume percentage of PTFE/PEEK blends is investigated using Scanning Electron Microscopy. The permittivity and loss tangent of the blends up to 40 MHz are studied using a Precision Impedance Analyzer. The variation of permittivity with respect to temperature (τ_εr) of the composite blends are also measured in the 0–100°C temperature region using a microprocessor controlled hot and cold chamber. The microwave dielectric properties of the polymer blends are studied in the X‐band (8.2–12.4 GHz) region by waveguide cavity perturbation technique using a Vector Network Analyzer. Rectangular cavity resonator is used to measure the complex permittivity of the PTFE/PEEK blends. Different modeling approaches are used to predict the theoretical permittivity of the blends and the results are compared with the experimental values. POLYM. COMPOS., 2009. © 2008 Society of Plastics Engineers     

Residual deposits in green tea shoots and black tea after individual and combined application of propiconazole and copper oxychloride

BACKGROUND: A combination of propiconazole and copper oxychloride is commonly used for controlling blister blight disease caused by the fungus Exobasidium vexans Massee of tea in south India. Field trials were conducted in wet and dry seasons to determine the rate of dissipation of propiconazole and copper oxychloride (COC) in green tea shoots and black tea. High‐performance liquid chromatography was used to quantify propiconazole residues in these matrices. Copper was analysed using atomic absorption spectrometry. RESULTS: The rate of dissipation of propiconazole in both seasons followed first‐order kinetics. Dissipation was faster in the wet than in the dry season. Factors such as rainfall elution and leaf growth dilution lead to faster residual decline in the wet season. However, even in wet season 0.10 mg kg^?1 of propiconazole residues were noted in black tea on the seventh day after fungicide application because of its systemic nature. Thus good control over the disease could be achieved. CONCLUSION: The recommended safe harvest interval and half‐life for the combined application of propiconazole and COC from this study is 5.39 and 2.43 days respectively in green tea shoots during the dry season. Moreover, the residues of propiconazole in green tea shoots on the seventh day is the same as the maximum residue limit (MRL) proposed by the European Union (EU), indicating that combined application of the two chemicals does not leave significant residues on seventh day or thereafter. Hence, upon harvest, which is usually between 8 and 10 days after fungicide application, the green tea shoots are safer from fungicide residues and pose less risk to human consumption. Copyright © 2009 Society of Chemical Industry     

Development of Empirical Correlation for Heat Transfer to Nanofluids

Nanofluids are emerging as alternative fluids for heat transfer applications due to enhanced thermal properties. Several correlations are available in open literature for heat transfer coefficient (HTC) and thermophysical properties of nanofluids. Reliability of correlations that use effective properties for estimation of HTC needs to be checked. Comparison of experimental HTC and that estimated from existing correlations is the main objective of the present study. An empirical correlation is developed with experimental data of the HTC for zinc–water and zinc oxide–water nanofluids. Experimental HTC is compared with that estimated from developed correlation and existing correlations. The range of Re considered for the study is 4000 to 18,000. Comparison indicated large deviation in experimental values and the values estimated from existing correlations. Based on comparison results, it can be concluded that the single‐phase models of forced convective heat transfer cannot be extended to nanofluids.     

Enhanced radiation from an electrically small radiator using an array of sub-wavelength holes

An experimental demonstration of radiation enhancement from an electrically small antenna (ESA) using an array of sub-wavelength holes engraved on a metallic plate is presented in this paper. A weakly radiating, chip inductor loaded open coplanar waveguide transmission line is used as the reference ESA. We show that an array of sub-wavelength hole loaded metallic aperture, placed near the antenna, can significantly enhance radiated power from the source. The hole array converts the high spatial reactive spectrum existing in the near-field of the antenna into a far-field propagating spectrum. The theory is validated by experiments and simulations in the microwave frequency regime. This novel radiation enhancement scheme is seen to enhance the gain of the antenna from ?8.5 to ?2.5?dBi and radiation efficiency from 13 to 33% around resonance.     

Radar cross-section enhancement of dihedral corner reflector using fractal-based metallo-dielectric structures

Effective use of fractal-based metallo-dielectric structures for enhancing the radar cross-section (RCS) of dihedral corner reflectors is reported. RCS enhancement of about 30 dBsm is obtained for corner reflectors with corner angles other than 90deg. This may find application in remote sensing and synthetic aperture radar     

Microwave assisted synthesis, spectroscopic, thermal, and antifungal studies of some lanthanide(Ⅲ) complexes with a heterocyclic bishydrazone

A bishydrazone formed by the condensation of isatinmonohydrazone and salicylaldehyde reacted with lanthanide(Ⅲ) chloride to form complexes of the type [Ln(HISA)2Cl3], where, Ln=La(Ⅲ), ce(Ⅲ), Pr(Ⅲ), Nd(Ⅲ), Sin(Ⅲ), Eu(Ⅲ), or Gd(Ⅲ) and HISA=[(2-hydroxybenzaldehyde)-3-isatin]bishydrazone. Both reactions were carried out under microwave conditions. The ligand and the metal complexes were characterized on the basis of elemental analysis, molar conductance, magnetic susceptibility measurements, UV visible, infrared, far infrared, and proton NMR spectral data. The ligand acted as neutral tridentate, coordinating through the carbonyl oxygen, azomethine nitrogen, and phenolic oxygen without deprotonation. The ligand and lanthanum(Ⅲ) complex were subjected to X-ray diffraction studies. The X-ray diffraction pattern of ligand exhibited its crystalline nature and that of the lanthanum(Ⅲ) complex indicated its amorphous character. The thermal decomposition behaviour of the complex, [La(HISA)2Cl3], was examined in the temperature range of 40-800 ℃ using TG, DTG, and DTA. The ligand and the metal complexes were screened for their antifungal activities.