Raw milk in cheeses doesn't pose same risk, prof says

TheRecord.com

August 09, 2008

Luisa D'Amato
RECORD STAFF

WATERLOO REGION

Popular cheeses such as Parmesan, Emmenthal and old cheddar are often made from unpasteurized milk, but they don't present the same health risks that fresh raw milk does, an expert at University of Guelph says.

Fully pasteurized milk is subjected to a temperature of 72 C for 16 seconds, which kills most of the harmful organisms in milk so that it's safe to drink.

But there's another process used for milk, called "heat-treating," in which the milk is held at a lower temperature: 55 to 65 C for 16 seconds. This doesn't pasteurize the milk; it kills dangerous bacteria but leaves a wider range of bacteria alive, says food sciences professor Art Hill.

And it's these other bacteria that give the cheeses their flavour.

Meanwhile, the cheesemaking process, which often involves "cooking" the cheese curds for hours at temperatures resembling a very hot bath, is a further guard against harmful bacteria.

So is the aging process.

Overall, the drier and harder that cheese made from unpasteurized milk is, the safer it is to eat. Parmesan cheese has no safety issues, Hill says. Raw-milk cheddar presents more risk, but it's still a very small risk.

Hill said he will eat raw-milk cheddar with no concerns. "But I wouldn't give it to my immune-compromised grandmother."

Cheeses made from raw milk are legal in Ontario, provided they've been aged for 60 days.

Quebec recently changed the law to allow some raw-milk cheeses aged less than 60 days, mostly to allow for the production of raw-milk Camembert.

The rationale is that this cheese is riskier to eat the longer it ripens.

Some of these cheese are made from heat-treated milk, others from milk that hasn't been treated at all.

ldamato@therecord.com