An alternative process for cleaning knives used on meat slaughter floors

Traditionally on slaughter floors operator knives are cleaned by rinsing in hand wash water at 20-40 °C followed by brief immersion in baths termed “sterilisers” which contain water no cooler than 82 °C. Under Australian legislation, both domestic and export, it is possible for a meat processing establishment to apply to the Controlling Authority for permission to implement an alternative procedure providing that it is at least the equivalent of that legislated. No firm evidence appears to exist for the 82 °C requirement and the possibility of replacing this element of the knife cleaning procedure with an alternative procedure using 60 °C water and a longer immersion time was investigated at an abattoir slaughtering cattle and sheep. Knives were tested at a range of work stations located along beef and mutton slaughter floors for Aerobic Plate Counts (APCs) and E. coli. For knives used on the beef chain the mean log APC/cm2 was 2.18 by the current knife cleaning process and 1.78 by the alternate procedure (P < 0.001). Using the current system E. coli was isolated from cleaned knives on 20/230 (8.7%) occasions compared with 21/230 (9.1%) occasions using the alternative system. The mean log E. coli of positive knives was 0.43/cm2 and 0.61/cm2 from the current and alternative systems, respectively. On the mutton chain the mean log APC/cm2 was 1.95 using the current knife cleaning process and 1.69 by the alternative procedure (P = 0.014). Using the current system E. coli was isolated from cleaned knives on 24/130 (18.5%) occasions compared with 29/130 (22.3%) occasions using the alternative system. The mean log E. coli of positive knives was 0.90/cm2 and 0.76/cm2 from the current and alternative systems, respectively. It is concluded that using two knives alternatively, rinsing them in hand wash water, then immersing them between uses in 60 °C water provides a microbiological outcome equivalent to rinsing them and momentary dipping in 82 °C water.