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
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
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
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.”