Dairy products are open to E.coli contamination because of the prevalence of the bacteria in animal waste, one disease expert says.
The warning comes after dairy giant Fonterra issued an urgent recall of four of its fresh cream products last night, over fears it may contain the E.coli bacterium.
Almost 9000 bottles of Anchor and Pams branded cream, which have been distributed to shops and food service outlets across the North Island, are affected by the recall.
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Fonterra Brands NZ managing director Peter McClure said the company was sorry for the inconvenience and concern the recall might cause "but food safety and quality are our top priorities".
People were advised not to use the cream, but to return it to where they bought it for a refund.
Mr McClure said signs of E-coli were discovered during standard testing yesterday morning.
The tests showed an unusually high "spike" of coli form in fresh cream at Fonterra's Takanini plant in South Auckland.
Three samples were sent for independent testing, which confirmed the contamination.
"All three samples they tested at an independent lab showed positive results for E.coli," Mr McClure said.
The results were "very, very unusual".
"In the last 20-odd years we've never had an incident of E.coli in milk despite periodic spiking in coliforms."
Professor Kurt Krause, head of the biochemistry department at Otago University and director of the Webster Centre for Infectious Diseases, said there is "an awful lot of opportunity" for E.coli contamination of dairy products because the bacteria is commonly found in faeces and animal waste.
He said Fonterra still has a lot of questions to answer before the true extent of the bacteria find could be known.
"Was there a problem with the process of carrying out the normal food safety procedures and processing this cream, or was there another cause of the contamination?
"I'm thinking that cream and milk and dairy products like this are pasteurised, and pasteurisation is highly effective at reducing the counts of E.coli, which otherwise would be much more numerous. So did the pasteurisation break down, was it not pasteurised, did something in the system break down? I think we need more information from Fonterra before we can make any judgement."
Mr McClure said the cause of the contamination was being investigated and answers were expected "in a few days".
Meanwhile, Labour's primary industries spokesman Damien O'Connor hit out at the Government, saying the recall "once again tests the credibility of our food safety systems".
He said the timing of food testing and the accuracy of information provided to companies, such as Fonterra, "needs further scrutiny".
Mr O'Connor called for a stand-alone food safety agency to ensure food production "can be accurately and independently monitored".
"Fonterra is our biggest company, food production is our biggest export, and New Zealand cannot afford mistakes that can further damage our international reputation."
Affected batch numbers:
* Pams Cream 500ml - 1400684206 - best before date 21/01/2014
* Anchor Cream 500ml - 1400684207 - best before date 21/01/2014
* Anchor Cream 300ml - 1400684208 - best before date 21/01/2014
* Pams Cream 300ml - 1400684209 - best before date 21/01/2014.
Fonterra contamination timeline:
• March 2013: Fonterra becomes aware of a possible "quality issue" with 38 tonnes of whey protein concentrate WPC80 produced at its plant in Hautapu, Waikato in May 2012.
• Late June: After other testing failed to rule out a botulism-causing strain of bacteria, Fonterra asks AgResearch to investigate.
• August 1: Fonterra chief executive Theo Spierings is told test results suggest the botulism-causing bacteria could be present in some batches.
• August 2: Fonterra informs the Ministry for Primary Industries and eight customers about the issue. Just after midnight it goes public with the contamination threat.
• August 28: MPI announces the scare was a false alarm - the bacterium was Clostridium sporogenes, which had no safety issues.
• September 7: It emerges AgResearch was not accredited to carry out the test by Crown entity International Accreditation New Zealand. It also emerges that a lab mouse, which died after being injected as part of the AgResearch tests, sparked the botulism fears.
• September 11: Trade Minister Tim Groser announces a $2 million Government support package aimed at helping small-to-medium-sized companies restore confidence in their markets abroad after the scare.
• October 29: An independent inquiry finds Fonterra failed to recognise the "explosive reputational risk" involved in the botulism scare.
• October 31: Fonterra is forced to dump 150,000 litres of raw milk after the potential contamination of 14 milk tankers with mud and gravel. The co-operative insists it is a "very minor incident".
• December 11: The first stage of a Government report into the scare is released. It calls for stronger systems to track dairy products through domestic and international supply chains, but denies there was a "failure" in food safety regulations.
• January 8, 2014: French food giant Denone announces it has begun a High Court claim against Fonterra for compensation after it recalled infant formula products in eight countries during the botulism scare, which it said cost it $576 million.
• January 13: At 9pm Fonterra issues a statement, saying it is recalling 8700 bottles of fresh cream under its Anchor and Pams brands because of a potential E.coli contamination after quality tests came up positive for the bacteria.