Decontamination of Escherichia coli biofilms on spinach by thermosonication and organic acid treatment

In this study, the effects of ultrasonication and organic acid treatment on Escherichia coli biofilms on spinach were investigated. Sonication process at different solution (PBS, lactic acid and acetic acid), temperature (20, 40 and 50oC) and time (2 and 5 minutes) was used for decontamination of spinach leaves with E. coli biofilm. The effects of temperature, time and inactivation solution on the inactivation of E. coli biofilm on spinach were found to be statistically significant (p<0.05). With the sonication process under different conditions, reduction in viable cell counts of E. coli biofilm on spinach was changed between 1.02 and 6.03 log cfu/cm2. The highest E. coli biofilm inactivation in spinach was achieved by lactic acid treatment under sonication conditions at 50oC for 5 minutes, while the lowest biofilm inactivation was achieved by PBS treatment under sonication conditions at 20oC for 2 minutes. According to standardized regression coefficients, the order of relative importance of the independent variables on the biofilm inactivation rate was indicated as temperature, solution, and time. It has been determined that decontamination processes applied to spinach generally do not have a negative effect on sensory properties, but sensory properties are significantly reduced in samples treated with acetic acid at high temperatures. As a result, lactic acid and thermosonication treatment have been suggested for effective decontamination of fresh leafy vegetables such as spinach.