Put 'em under pressure

Pressurising food kills bacteria and can lead to unexpected new products, reports Dick Ahlstrom

'Put 'em under pressure" was Jack Charlton's straightforward advice as manager of the Ireland football team. Researchers at University College Cork have put his simple admonition to work in the area of food preservation and the development of food products.

A team in the department of food and nutritional sciences has been studying the use of very-high-pressure processing as a way of killing bacterial contaminants, speeding up the ripening of cheese and helping to develop new food products.

"This is a very new technology and for the food industry it is a foreign concept," says Dr Alan Kelly, who leads a research group working in the area. With this in mind he has organised a conference next month on the use of high-pressure treatment of foods, to help people understand the technique and the opportunities.

"We have aimed it at food companies, but there is also significant interest from the State regulatory bodies and agencies," says Kelly. "We also have quite a bit of interest from retailers who may see these products coming on stream in the near future."

When Kelly talks about high pressure he means high pressure. His pilot system processes foods at between 1,000 and 10,000 atmospheres, which exceeds the pressures found at the deepest points under the oceans.

An American scientist, Bert Hite, discovered its value to food processing and decontamination more than 100 years ago, but his work was ignored for almost 80 years. It now provides a world focus as a powerful method of helping to make food safer.

No heat is used. Instead, the high pressures inactivate the bacteria, moulds and yeasts that can cause food spoilage or food poisoning. Its great advantage, says Kelly, is the fact that it usually does not affect flavour, nutritional value or texture, problems that arise when using pasteurisation. Despite the enormous pressures, food comes back out of the pressure chamber in much the same condition as it entered it.

Using the technique can lead to unexpected discoveries, says Kelly, who cites a US firm called Motivatit Seafoods as a prime example. "This company discovered by accident that if you put oysters under high pressure, it releases the muscle that holds the shell shut. This was a massive technological leap," he says.

The pressure treatment not only wipes out the bacteria that often populate live oysters but also opens up the shells without the sometimes dangerous fight with an oyster knife.

The company shrink-wraps a gold band around each oyster before processing. This keeps the oyster shut until the consumer is ready to eat it, says Kelly. "They have turned one of the least convenient products into a very convenient product."

No Irish food companies currently use high-pressure treatment, but UCC has joined with other centres to promote the technique. He works with Dr Tom Beresford of Teagasc's Moorepark research centre, in Co Cork, on studies related to treatment of dairy products.

UCC also collaborates with Queen's University Belfast, where Dr Margaret Patterson works with Kelly's team on pressure treatment of shellfish. UCC has also pursued research contracts with the Department of Agriculture and Food.

UCC received funding from the Higher Education Authority and Enterprise Ireland to buy a pilot pressure system, which it uses for research and to demonstrate the process to industrial food companies, says Kelly. This was installed late last year.

The team is already coming up with unexpected results. It typically takes a month to ripen mozzarella cheese, for example, but Kelly has found pressure treatment speeds it up considerably. "We can achieve full ripening in minutes with this process," he says. Analysis shows that pressurised cheeses have the same structure and key characteristics as naturally ripened versions.

"If we can understand the mechanism that causes this change it could open up a whole range of opportunities," he says.

Much fruit juice is pressure treated, for example. "Orange juice is like a flagship product for high-pressure treatment. We have an Enterprise Ireland- funded project to develop a range of nutritional juice-based products."

Pressure to Succeed: An Insight into High-Pressure Food Processing, a one-day conference, is at the Tullamore Court Hotel, Tullamore, Co Offaly, on April 9th. Full details are available from www.ucc.ie/fitu