Inactivation kinetics of inoculated Escherichia coli O157:H7, Listeria monocytogenes and Salmonella Poona on whole cantaloupe by chlorine dioxide gas.

The objectives of this study were to examine inactivation kinetics of inoculated Escherichia coli O157:H7, Listeria monocytogenes and Salmonella Poona inoculated onto whole cantaloupe and treated with ClO(2) gas at different concentrations (0.5, 1.0, 1.5, 3.0 and 5.0 mg l(-1)) for different times (0, 2.0, 4.0, 6.0, 8.0 and 10.0 min). The effect of ClO(2) gas on the quality and shelf life of whole cantaloupe was also evaluated during storage at 22 degrees C for 12 days. A 100 microl inoculation of each targeted organism was spotted onto the surface (5 cm(2)) of cantaloupe rind (approximately 8-9 log CFU 5 cm(-2)) separately, air dried (60 min), and then treated with ClO(2) gas at 22 degrees C and 90-95% relative humidity for 10 min. Surviving bacterial populations on cantaloupe surfaces were determined using a membrane transferring method with a non-selective medium followed by a selective medium. The inactivation kinetics of E. coli O157:H7, L. monocytogenes and S. Poona were determined using nonlinear kinetics (Weibull model). A 3 log CFU reduction of E. coli O157:H7, L. monocytogenes and S. Poona were achieved with 5.0 mg l(-1) ClO(2) gas for 5.5, 4.2 and 1.5 min, respectively. A 5l og CFU reduction of S. Poona was achieved with 5.0 and 3.0 mg l(-1) ClO(2) gas for 6 and 8 min, respectively. A 4.6 and 4.3 log reduction was achieved after treatment with 5.0 mg l(-1) ClO(2) gas at 10 min for E. coli O157:H7 and L. monocytogenes, respectively. Treatment with 5.0 mg l(-1) ClO(2) gas significantly (p<0.05) reduced the initial microflora (mesophilic bacteria, psychrotrophic bacteria, and yeasts and molds) on cantaloupe by more than 2 log CFU cm(-2) and kept them significantly (p<0.05) lower than the untreated control during storage at 22 degrees C for 12 days. Treatment with ClO(2) gas did not significantly (p>0.05) affect the color of whole cantaloupe and extended the shelf life to 9 days compared to 3 days for the untreated control, when stored at ambient temperature (22 degrees C).

Microbial heat resistance of Listeria monocytogenes and the impact on ready-to-eat meat quality after post-package pasteurization.

Several methods using bactericides, hydrostatic pressure, and post-package pasteurization technologies to control Listeria monocytogenes (LM) in ready-to-eat meats have been attempted. In addition to controlling LM contamination, any newly developed technology must have minimal effects on organoleptic properties. The objectives of this study were to: (1) determine the heat resistance of LM in two brands (A and B) of bologna differing in formulations, and, (2) evaluate the effects of post-package pasteurization on product quality. Fat content did not affect LM heat resistance in bologna at 55, 60, and 65°C; however, Brand B bologna had a numerically lower inactivation rate. Microbial heat resistance differed (P<0.05) with changes in pasteurization temperature. Time and temperature affected (P<0.05) cook-loss and L(∗) Hunter color value for both bologna brands. These data show that post-package pasteurization is effective but suggest that meat formulations may need modification to prevent development of negative quality characteristics.

Elastohydrodynamic Lubrication of Porous Substrates. Application to Synovial Joint Analysis.

This work presents computational results for an elastohydrodynamic model with a porous wall. The model - inspired by the cartilage exudation phenomenon arising in living joints - allows the lubricating fluid to be transferred from the porous walls to the flow channel and viceversa. The system is represented through a strongly coupled set of nonlinear equations which involves hydrodynamic lubrication, plane elasticity and continuity in porous media. The solution technique employed is based on the finite element method, Newton iteration and parametric continuation processes. The predictions obtained uncover mechanisms that might be responsible for the extremely low friction coefficients found in synovial joints.