Milk and fresh juices could soon taste better and stay fresh longer, thanks to a breakthrough pasteurization method developed at the University of Georgia.

The new method uses high pressure instead of heat.

"Right now, the process of heating changes the flavor of juices and milk," said Romeo Toledo, a food scientist with the UGA College of Agricultural and Environmental Sciences. "The result is a cooked flavor that many people can detect."

In some cases, the current pasteurization process can even change a product's color.

"In intense cases, the product can turn brown," Toledo said. "In mild cases, the color doesn't change. But the flavor still does. The difference isn't quite as detectable in milk as it is in juices."

The flavor change was just one reason UGA scientists sought a new pasteurization method.

"Three or four years ago, an outbreak of E. coli was linked to unpasteurized apple juice," Toledo said. "The processors don't want to pasteurize their juices because it changes the flavor and people won't buy it. But they also know people won't buy it if it could make their families sick."

Toledo said apple and orange juices can contain E. coli and Salmonella if not properly pasteurized. "This is because the fruit sometimes comes from farms where cattle graze in the orchards," he said.

Since the E. coli outbreak, the Food and Drug Administration requires processors of unpasteurized juices to place warning labels on their products.

"This isn't a large market. It's a specialty niche market," Toledo said. "People who buy this juice expect the flavor to be there."

Traditional pasteurization heats the product to at least 180 degrees to kill any microorganisms. Then it's cooled and stored.

S. Omahen, UGA CAES

HIGH- PRESSURE PASTEURIZATION keeps juice fresh without heat. Above, UGA research coordinators pour orange juice into the new device. Below, the juice is bottled for storage.

S. Omahen, UGA CAES

Toledo's new method uses high pressure. "We subject the juice or milk to high pressure and then suddenly drop the pressure," Toledo said. "When we drop the pressure, we pass the liquid through a small opening at a very high velocity -- almost at the speed of sound."

Toledo said the pressure breaks apart and destroys the microorganisms' cells. Tests show it kills a greater percentage of microorganisms than heat pasteurization.

As if that weren't enough, it also extends the shelf life.

"Fresh-squeezed fruit juices are limited to about a 10- day shelf life now," Toledo said. "With the new method, you could have a shelf life of up to two months."

In his Athens lab, Toledo has bottles of milk that were pasteurized four months ago and are still fresh -- "as long as you don't open the bottle," he said. "Once you open the bottle, it will start toÿ go bad just like traditionally pasteurized milk."

Saving the product's original flavor could also open the market for new products.

"Many specialty cheeses lose their flavor as a result of heat pasteurization," Toledo said. "They could now be processed using the high-pressure method."

Toledo has processed peaches, a fruit that historically loses flavor during processing, with great results.

"Using this system, the peach juice tastes like you squeezed it right out of the fruit," he said. "You can't tell the difference."

Taste panelists loved the samples processed by the new method. "Most couldn't tell the difference between our product and fresh-squeezed," Toledo said.

The new method even helps milk curdle better. "The milk produced yogurt with a firmer curd," Toledo said. "Traditionally processed milk doesn't produce a very firm curd. Yogurt producers have to add gums to increase the consistency."

UGA has filed for a patent on the high-pressure pasteurization method and is working closely with industries that may adopt it.

"The next step will be to scale up our prototype for industrial use," Toledo said. "We're demonstrating the method to potential industries. We hope to see someone begin using it over the next couple of years."