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 (ClO2) for Salmonella Typhimurium and Escherichia coli inactivation in poultry processing chiller tank water. A Full Factorial Design (FFD) 22 was conducted for each microorganism to evaluate the effect of ultrasound exposure time (x1: 1 to 9 min; fixed: 37 kHz; 330 W; 25 °C) using a bath, and ClO2 concentration (x2: 1 to 17 mg L-1) on microorganism count expressed in log CFU mL-1 in distilled water. Variable x2 had a negative effect on Salmonella Typhimurium (-5.09) and Escherichia coli (-2.00) count, improving the inactivation; while a x1 increase present no inactivation improvement, explaining the use of x1 lower level (1 min) and x2 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; x1 was kept (1 min), however x2 was adjusted to obtain the same residual free chlorine (2.38 mg L-1) considering the ClO2 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 ClO2, 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 ClO2 was more pronounced, with microorganisms' reductions up to 100%.