Audit and Relative Risk Assessment of Harvest Processing Equipment Sanitization in Commercial Packing Plants

Background

Hot (82◦C) water is an effective, and the most common, method to sanitize knives, air knives, etc. in commercial packing plants, when it’s done right. The problem is, we don’t really know what the appropriate combination of water temperature, immersion depth and immersion time are for different types and sizes of cutting equipment. Metal heats up at different rates, depending on size, thickness, porosity, etc. In contrast, the pace of production in commercial beef processing is very consistent – at a harvest rate of 350 animals per hour, a maximum of approximately 10.3 seconds exists between animals. Job tasks and sanitation procedures must both be completed within this constant time.  

We also don’t have a clear understanding of what employees are actually doing when sanitizing their equipment. This research will determine whether we are telling processing employees to do the right thing, and whether they are doing it.  

This research determined the frequency at which beef processing employees are correctly practicing sanitation behaviors, the heating rates and duration needed to achieve thermal sanitation of multiple processing equipment, and the log reduction in E. coli that can be expected when equipment are immersed in hot water for different durations. 

Objectives

• Audit beef processing workers’ sanitation practices of pieces of slaughter equipment used in critically important hide removal tasks,
• Determine the relative food safety risk of abattoir processing equipment and factors affecting sanitation effectiveness, and
• Establish time-temperature thresholds of direct contact beef processing equipment to reduce microbial cross-contamination.

What they Did

The research team audited (in-person and via camera) sanitation behaviors (e.g. handwashing frequency, contamination frequency, equipment sanitation frequency) of Canadian beef processing employees performing tasks (hide removal) considered critical to avoiding microbial contamination of the carcass. They also determined how long different pieces of beef processing equipment needed to be immersed at different temperatures in order to achieve thermal sanitation.  

In a federal research laboratory, knives with different degrees of wear were sanitized, inoculated with E. coli, and immersed in hot water following the commercial sanitation practices observed in the first trial, to determined bacterial survival. The researchers also examined the effectiveness of multiple methods of cleaning knives without hot water. 

What They Learned

Audit data revealed sanitation immersion times for equipment ranged from less than 1 second for rotating power knives to upwards of 20 seconds for straight and skinning knives. Four pieces of equipment (rotating power knives, brisket saws, pneumatic de-hiders, leg clippers) are not likely to be adequately sanitized at the pace of production. However, the remaining harvest equipment received adequate sanitation duration. Hand washing and equipment sanitation frequency were adequate; additional attention needs to be paid to hook sanitation.  

Skinning and straight knives were able to reach thermal sanitation in less than 7 seconds. However, the pneumatic de-hider, leg clippers, and brisket saw blades required more time than employees are allotted between animals to achieve thermal sanitation.  

E. coli was adequately eliminated when knives were properly sanitized in hot water. However, flash dipping of knives provided almost no sanitation benefit. Knives treated with lactic acid were less effectively sanitized than when peroxyacetic acid was used. Lactic acid and ESAN sanitizers reduced residual protein build-up on knives compared to controls.  

Ultraviolet light did not reduce E. coli populations rapidly enough to be useful at the pace of production. However, UV-C may be valuable for sanitizing knives during breaks, shift changes, or overnight. 

What It Means

Audit outcomes suggest that more time is needed to sanitize large equipment. Installing multiple pieces of equipment for these tasks (similar to a multi-knife system) could also allow for sufficient hot water sanitation time. Processors can use these data to modify Sanitation Standard Operating Procedures or train/re-train employees. These data support the use of audits to continually monitor food safety behavior.