Single step non-thermal cleaning/sanitation of knives used in meat industry with ultrasound.

The combination of ultrasound (US) with chlorinated water (CW) and neutral detergent (ND) for simultaneous cleaning and sanitation of knives used during cattle slaughter was evaluated as a novel non thermal treatment. The US mode of operation, detergent concentration and time of treatment were studied and the results were compared with the conventional sanitation method used in meat industries. The conventional sanitation method promoted a decrease (p<0.05) in the counts of mesophiles, Enterobacteriaceae, molds and yeasts, and a similar behavior was observed for US+CW (2.05±0.08mg/l of chlorine, and mode operation normal and sweep for 10min) and US+CW+ND (5ml/l and mode operation sweep for 5min) methods. Nevertheless, when detergent concentration and sonication time were increased (20ml/l, 15min) a strong decrease (p<0.05) in the counts of mesophiles, Enterobacteriaceae, Staphylococcus aureus, molds and yeasts. Knife blades presented appropriate hygienic-sanitary properties in such conditions based on the Clean-Trace Surface Protein Plus™ test swab, which were better than the results obtained from conventional method. Kinetic modeling of knife sanitation was performed according to the transfer of organic matter, nitrogen and phosphorus during the process indicated highest migration rate of residues for US+CW+ND method, reaching 1.61mg/l·min. The hardness of knives' surface (Rockwell) was not changed by sonication using US+CW+ND method. These results indicate that both knife cleaning and sanitation processes could be performed in a unique step without the use of heat.