Routine microbiological testing undertaken by dairy processors occasionally detects E.coli in dairy products, however in the majority of instances this is picked up prior to the product leaving the manufacturer.
Nationally, between 2019 and early 2022, there were 14 consumer level recalls of dairy products due to E.coli contamination, covering milk, cheese, butter and kefir. This includes one in SA in 2019.
E.coli was responsible for 20% of the 201 food recalls (all food commodities) in Australia between 2012 and 2021.
The presence of E.coli in food – including dairy products – doesn’t necessarily mean the food is unsafe, however it does mean there has been a process failure, the product could cause illness and further testing is needed.
E.coli is one of a number of microorganisms significant for food safety management tested for by the dairy industry. It’s an important organism because it is a faecal indicator and can signal pathogens (e.g., Salmonella) may be present.
In all dairy animals (cows, sheep, goats, buffalo), faecal contamination during milking can be a common occurrence, even in the most hygienic operations, because of the location of the anus above the udders. This has been demonstrated through surveys where 80-100% of raw milk vats showed E.coli presence.
E.coli can become established in processing environments and can grow on inadequately cleaned surfaces and in food. It is killed by the standard thermal processes applied in food production and can be readily removed from food processing equipment and surfaces by appropriate cleaning procedures.
Testing for E.coli has long been used in the dairy industry to indicate contamination in pasteurised products. Testing of this kind is a key component of any food safety program.
It is a useful tool to support through-chain food safety control measures and microbiological criteria have been established as part of Australia’s food safety management arrangements to support decision making, to verify process hygiene, and to confirm process controls are working as intended.
Manufacturers send product to NATA accredited laboratories as part of routine microbiological testing to verify controls have worked as intended.
Product testing is an important component of an effectively operating food safety program and is accompanied by effective corrective and preventive action. Identifying a micro breach is an early warning of process control failure and can assist with continuous improvement.
Exceeding a target level for indicator organisms such as E.coli prompts an investigation into the cause, followed by corrective action to rectify the issue and prevent it from recurring.
When process hygiene criteria are not met, this can indicate that a specific control step is not working as effectively as it should, which provides an opportunity for early intervention.
Tracking the source
Pasteurisation is designed to provide more than enough heat to eliminate E.coli (and other pathogens), so when tracking the source of E.coli contamination, dairy processors should consider first checking that the correct temperature and time is being delivered by the pasteurisation process.
Where a micro breach has occurred and the pasteurisation time/temperature records indicate no failures, processors should look for potential post-pasteurisation contamination points, for example:
- Leakage between raw and heated sides in the plate heat exchanger.
- Bacteria surviving in the foamy headspace of a batch pasteuriser or drips entering when the equipment is opened.
- Contamination at the filler.
- Contamination in the lines.
Post-pasteurisation contamination can also come from the environment, via transferring organic contamination, and directly from people, usually due to hygiene failure.
Further information about E.coli and other microbes important to dairy can be found on Dairysafe’s website: