Modeling inactivation kinetics of liquid egg white exposed to UV-C irradiation

The efficiency of UV-C irradiation as a non-thermal pasteurization process for liquid egg white (LEW) was investigated. LEW inoculated with Escherichia coli K-12 (ATCC 25253), pathogenic strain of Escherichia coli O157:H7 (NCTC12900) and Listeria innocua (NRRL B33314) were treated with UV light using a bench top collimated beam apparatus. Inoculated LEW samples were exposed to UV-C irradiation of known UV intensity of 1.314 mW/cm² and sample depth of 0.153 cm for 0, 3 5, 7, 10, 13, 17 and 20 min. The populations of E. coli K-12, E. coli O157:H7 and L. innocua were reduced after 20 min of exposure by 0.896, 1.403 and 0.960 log CFU respectively. Additionally, the inactivation data obtained for each strain suspended in LEW was correlated by using Weibull (2 parameter), Log-Linear (1 parameter), Hom (2 parameter) and modified Chick Watson (2 parameter) models. The inactivation kinetics of E. coli K-12, E. coli O157:H7 and L. innocua were best described by modified Chick Watson model with the smallest root mean squared error (RMSE) (R² ≥ 0.92).     

Inactivation of Listeria monocytogenes on a polyethylene surface modified by layer-by-layer deposition of the antimicrobial N-halamine

Modification of food contact surfaces to be antimicrobial represents an approach to address the problem of cross-contamination in the food industry. The effect of increasing levels of surface modification on low density polyethylene (LDPE) through application of N-halamines on the inactivation kinetics of Listeria monocytogenes Scott A was evaluated. Increasing levels of modification were applied through layer by layer deposition on LDPE surface (1–5 double layers of polyethyleneimine and poly(acrylic acid)). Surface modification was achieved and confirmed through Fourier Transform Infrared Spectroscopy (FTIR). From 1 to 5 double layers, the N-halamine content ranged from 3.42 ± 1.2 to 27.30 ± 3.5 nmol cm⁻². More than four logarithmic cycles (>99.99%) reduction was reached against L. monocytogenes Scott A after different contact times depending on the level of modification, that varied from 50 to 110 min (from 5 to 2 double layers). Inactivation kinetics followed a sigmoidal behavior.