Effect of ultrasound and chlorine dioxide on Salmonella Typhimurium and Escherichia coli inactivation in poultry chiller tank water

This study evaluated the application of ultrasound alone or combined with chlorine dioxide (ClO(2)) for Salmonella Typhimurium and Escherichia coli inactivation in poultry processing chiller tank water. A Full Factorial Design (FFD) 2(2) was conducted for each microorganism to evaluate the effect of ultrasound exposure time (x(1): 1 to 9 min; fixed: 37 kHz; 330 W; 25 °C) using a bath, and ClO(2) concentration (x(2): 1 to 17 mg L(−1)) on microorganism count expressed in log CFU mL(−1) in distilled water. Variable x(2) had a negative effect on Salmonella Typhimurium (-5.09) and Escherichia coli (-2.00) count, improving the inactivation; while a x(1) increase present no inactivation improvement, explaining the use of x(1) lower level (1 min) and x(2) higher level (17 mg L(−1)). The best condition for microorganism inactivation based on FFD was evaluated in chiller tank water (with organic matter) at 25, 16, and 4 °C; x(1) was kept (1 min), however x(2) was adjusted to obtain the same residual free chlorine (2.38 mg L(−1)) considering the ClO(2) consumption by organic matter, achieving the value of 30 mg L(−1). An inactivation of 49% and 31% were observed for Salmonella Typhimurium and Escherichia coli. When ultrasound was replaced by a simple agitation in the presence of ClO(2), there was no inactivation for both microorganisms. Moreover, at poultry carcass pre-chilling (16 °C) and chilling (4 °C) conditions, the synergism of ultrasound combined with ClO(2) was more pronounced, with microorganisms’ reductions up to 100%.