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Effect of pulsed light treatment on inactivation kinetics of Escherichia coli (MTCC 433) in fruit juices

The inactivation kinetics of Escherichia coli (MTCC 433) inoculated in the tender coconut water, orange and pineapple juice was investigated using a laboratory model continuous flow pulsed light system with a fixed flow rate of 100 ml/s and the experimental data were fitted with different inactivation models. The E. coli inactivation was examined by the effect of pulsed light fluence rate (0.18, 2 and 5.6 W/cm2) and exposure time (between 0 and 15 s). Log reduction of maximum 4.0, 4.5 and 5.33 was determined in orange, pineapple juice and tender coconut water, respectively, when treated with the pulsed light doses of 95.2 J/cm2, which follows the FDA recommendation. The Weibull, Biphasic and Log linear plus tail models were compared to predict the survival curves of E. coli. Inactivation kinetics of E. coli for liquid foods used in this study were best fitted by weibull model (R2 = 0.9926 to 0.9989; RMSE = 0.0462 to 0.0981). The E.coli inoculated liquid foods treated with pulsed light resulted in flattening out of the cells from the edges due to its membrane integrity degradation which were examined using scanning electron microscopy. Pulsed light could be an effective alternative non-thermal treatment for the pasteurization of liquid foods.