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.”