A salmonella outbreak linked to popular pre-packaged lettuce is a "great concern" for Australia's $8.6 billion fresh fruit and vegetable industry and could undermine the nation's enviable clean and green reputation, says horticulture doyen Frank Costa.

Mr Costa, who has been a prominent figure in the industry for more than six decades, said he was shocked to hear of the contamination which stemmed from lettuce grown by the Ruffo family-owned Tripod Farmers and sold in Coles, Woolworths and other grocers.

He said he had never heard of such an outbreak, which has already put two people in hospital.

"We take great care in everything we do here but then I'm sure the other companies dealing in fresh produce are also quite vigilant so I don't know how this could have happened," Mr Costa said.

"It is a great concern for the whole industry and the industry will be doing everything in its power, as we will be as individuals, to make sure we check, check and double check all of our business."

Metcash, Coles and Woolworths had pulled all Tripod Farmers product from their shelves on Friday as shoppers took to social media to vent their anger that the major chains had sold salmonella-tainted lettuce.

The recall extended to beyond the major grocery chains, with Lite n' Easy and Aussie Farmers Direct confirming they had used Tripod products in their home deliveries.

Export threat

But the contamination scare is not just a domestic issue. It has the potential to infect our biggest trading partners, including China.

Australia's exports about $2.1 billion – almost a quarter of the value of total industry – of fresh fruit and vegetables each year, according to Austrade.

A key part of export success has been Australia's clean and green image, particularly in China, where food safety has become a big issue after several domestic contamination scandals.

Such is the sensitivity in China – Australia's biggest export partner – on food safety that it temporarily banned imports from New Zealand dairy company, Fonterra, in 2013 after it recalled products following a positive test for botulism. This was despite that test eventually proving to be false.

"We certainly are very careful and very protective of our product because your reputation is critical … to grow your business," Mr Costa said.

He said the Chinese market was "very sensitive" and "a terribly important one for Australia".

"That's something that will be of great concern for everybody in our industry.

"We export to China and now we grow product in China, which is good and is looking very promising. They love Australia and they love our produce. We have got that nice clean, green image and we have to do absolutely everything to protect it."

A spokesman for the Minister for Agriculture, Barnaby Joyce said Australia's reputation "as a producer of clean, green, high-quality produce is one of our greatest trading advantages.

"Mr Joyce shares Mr Costa's concern that we protect that reputation at all costs.

"Through the Department of Agriculture, importing country requirements are rigorously addressed through Australian Government accredited systems and processes.

"We are working closely with our trading partners to ensure that any product that potentially poses a risk does not reach the shelves."

Supermarket fallout

But the salmonella outbreak, which appears to be confined to Tripod Farmers, won't just threaten exports if producers aren't vigilant.

"That's the sort of thing that can really bring confidence down for the consumers, and not just export but also our local consumers here," Mr Costa said.

"Fresh produce is important part of the shelves of the major supermarkets. It's probably the number one reason why a consumer picks a certain supermarket to do their shopping.

"If there are any thoughts from the shopper that the fresh produce might not be safe and healthy, well that would be very negative … going forward for all levels of the industry."

Tripod Farmers did not return calls from Fairfax Media.

Lettuce especially vulnerable

Produce Marketing Association technology manager Richard Bennett said lettuce was especially vulnerable to pathogens like salmonella because it grew so close to the ground.

Mr Bennett said the rough surface texture of lettuce trapped bacteria like salmonella.

This was the reason producers had to be rigorous in washing and agitating product before it was packaged to sell, he said.

He said salmonella bacteria was everywhere in the agricultural environment but it could just as easily have come from human handling of the leaves as it could from the ground or a piece of machinery.

"Eradicating salmonella would be like asking someone to eradicate oxygen, it's everywhere," Mr Bennett said.