Combined effect of thermosonication and organic acids against Escherichia coli biofilms on spinach leaves

The present work evaluated the effects of thermosonication treatment alone or in combination with organic acids on Escherichia coli biofilm destruction on spinach leaves and developed prediction model regarding its destruction. The effect of temperature (40 and 50 degrees C), time (2 and 5 min) and inactivation solution (lactic acid, acetic acid) on the inactivation of E. coli biofilms on spinach was usually found to be statistically significant. The highest (6.03 log CFU/cm2) and the lowest E. coli biofilm reduction (1.02 log CFU/cm2) were obtained with combined treatment of thermosonication and lactic acid at 50 degrees C for 5 min and with single sonication treatment at 20 degrees C for 2 min, respectively. The order of relative importance of the independent variables on the biofilm inactivation rate was indicated as temperature ((3 = 0.660), solution ((3 = 0.469) and duration ((3 = 0.266). Regarding properties of spinach quality after decontamination treatment, combination of thermosonication and acetic acid caused negative effects, while thermosonication treatment with lactic acid resulted in desirable effects. Additionally, microscopic observations demonstrated that the cell shape and greenness of spinach samples changed after sonication treatment. These findings suggested that thermosonication treatment combined with lactic acid may be a useful technique ensuring safety and quality of fresh produce.