Carbonated Milk Prolongs Freshness

Milk Kept Fresh In The Fridge For Months? Yes!

Imagine milk kept fresh in the refrigerator for months. Far-fetched? Not at

all, say Cornell University food scientists, who believe they have a way to

keep dairy products fresh and fortified for several months -carbonation, the

same kind added to carbonated drinks, but at lower levels.

“This will further enhance the safety of refrigerated, pasteurized milk by

ensuring that pathogenic bacteria will not grow,” said Joseph H. Hotchkiss,

Cornell professor of food science. He and colleagues previously demonstrated

that dissolved CO2 can extend the shelf life of cottage cheese by about 200

percent. Modified milk has been found to last more than two months in a

refrigerator, and it still tastes fresh and contains no dangerous

bacteria.

While carbonation has been used in soda for more than a century, the process

has not been applied to milk because the microbial activity of low amounts was

unknown and because the carbonation would dissipate in milk cartons. Further,

the method for inserting the carbonation was not efficient. Thanks to advanced

packaging technologies and more efficient carbonation processes, a new style

of fortified milk now is possible.

Consumers needn’t worry that milk now will start tasting like soda: the amount

of carbonation injected into the milk is below the threshold of taste

detection, according to Hotchkiss, but it is enough to stave off harmful

bacteria. “How much CO2 must be added depends on a number of factors,” he

said. “The upper limit is the amount which can be tasted in the fluid milk.

The lower limit depends on the desired shelf life and degree of barrier in the

package.”

The research was reported in an article, “Modified Atmosphere Packaging of

Fluid Dairy Foods for Consumer and Institutional Markets,” as part of the 1995

annual report of the Northeast Dairy Foods Research Center, the group that

funded the study.

“The amount of CO2 used is very small. The equipment to store and add the CO2

are relatively simple, and they are a one-time cost,” Hotchkiss said. “The

largest cost generally is in the improved packaging materials and equipment.

Longer shelf life requires better carton barriers, which cost more.”

While the technology used to insert the CO2 was tested in the cottage cheese

industry, the cartons to contain the fortified milk are made for the orange

juice industry. Thanks to ethylene vinyl alcohol (EVOH) coated cartons,

Hotchkiss believes that fluid milk will be able to maintain the carbonation.

“Right now, it’s our barrier of choice,” he said. “Whether consumers accept

this new technology or not will be settled in the marketplace.” The

technology could have far-reaching effects beyond the grocer’s shelves.

Hotchkiss said that fluid milk carbonation might have uses during the

transport of raw milk over long distances. In some parts of the country,

during the summer in Florida for example, milk is imported from northern

states because Florida’s heat severely reduces dairy production. Injecting CO2

into raw milk before it is processed improves the chances that the milk

arrives safely.

A process like this could mark a significant shift in how consumers regard

milk. About 11 percent of consumers’ total food expenditures are for dairy

products, according to the report. “Consumers demand high quality, and they

are sensitive to quality defects when purchasing dairy products. Off-flavors

are easily detected, especially in fluid milk,” Hotchkiss said. “Adding CO2 is

an economical way to extend the shelf life and improve the quality of

perishable foods in home storage as well as in retail distribution.”