Model could help improve milk's shelf life, reducing consumer waste

Blaine Friedlander
Cornell University

Researchers at Cornell University are working on a predictive model that demonstrates how lower temperatures could extend the shelf life of that carton of milk in consumers' refrigerators.

Research shows consumers often throw out "expired" food prematurely based on sell by or expiration dates contributing to unnecessary food waste.

Studies show that many consumers often toss food items out prematurely based on "sell-by" and "best-by" dates printed on cartons and packages.

"Putting dates on milk cartons is a big issue, because consumers often discard the milk if it is past eh sell-by date," said Martin Wiedmann, Cornell University professor of food safety and author of the study. "Often there is little science behind those dates, as they are experienced-based guesses."

Wiedmann says the goal of the research is to  put good science to use, reduce food waste and reduce food spoilage.

Cornell food scientists have created a new predictive model that examines spore-forming bacteria and when they emerge, according to research published last month in the Journal of Dairy Science.

While food safety processes like pasteurization helps to stem the growth of bacteria in milk, researchers say that sore-forming bacteria can survive under many conditions.

"When they have the opportunity to grow in pasteurized milk, they can cause off-flavors and curdling," said Ariel Buehler, the papers's lead author.

Research Support Specialist Nicole Martin at Cornell’s New York State Milk Quality Improvement Program laboratory.says that is a 'considerable problem.'

"If we can reduce the spoilage from spore-forming bacteria – by reducing their presence and by controlling their outgrowth – we can see the shelf life for milk improve from two weeks to perhaps a month,” Martin said.

The best way to reduce the presence of spores may be through the a microfiltration process, in which milk is treated to a very fine filtration process where it removes more bacteria than pasteurization.

Researchers say there is little science behind the "sell by" and "best by" dates on milk cartons.

This is already an emerging technology in the dairy industry

Researchers say that temperature is also key. The new model showed that refrigerated milk at 39.2 degrees dramatically lowers the mean concentration of spore-forming bacteria. By decreasing the refrigeration temperature from 42.8 degrees to 39.2 degrees, only 9 percent of milk half gallons were spoiled after 21 days, compared with 66 percent of half gallons held at the higher temperature, according to the report..

Wiedmann imagines a day – perhaps in five to eight years – when consumers find no dates stamped on milk containers. Instead, a scannable barcode could provide the milk’s production history and an accurate use-by date. Cartons could also sport a time-temperature indicator that communicates shelf-life prediction.

“This is the foundational work that could get us there, where consumers could manage their food inventory in the fridge,” said Wiedmann. “That’s the vision.”

Understanding packaging lingo

So, just how long is that package of lunch meat or carton of milk safe to eat? That's a question that many consumers ponder as they try to understand the date lingo on the packages of food. 

Types of Dates

A "Sell-By" date tells the store how long to display the product for sale. You should buy the product before the date expires.

A "Best if Used By (or Before)" date is recommended for best flavor or quality. It is not a purchase or safety date.

A "Use-By" date is the last date recommended for the use of the product while at peak quality. The date has been determined by the manufacturer of the product. 

"Closed or coded dates" are packing numbers for use by the manufacturer.

Safety after date expires

Except for "use-by" dates, product dates don't always refer to home storage and use after purchase. But even if the date expires during home storage, a product should be safe, wholesome and of good quality -- if handled properly and kept at 40° F or below.

Foods can develop an off odor, flavor or appearance due to spoilage bacteria. If a food has developed such characteristics, you should not use it for quality reasons.

If foods are mishandled, however, foodborne bacteria can grow and cause foodborne illness -- before or after the date on the package. For example, if hot dogs are taken to a picnic and left out several hours, they wouldn't be safe if used thereafter, even if the date hasn't expired.

Other examples of potential mishandling are products that have been: defrosted at room temperature more than two hours; cross contaminated; or handled by people who don't use proper sanitary practices. Make sure to follow the handling and preparation instructions on the label to ensure top quality and safety.