New Research and Useful Tips on Extending Shelf Life

Wouldn't you love it if the food you brought home from the grocery store and the leftovers you refrigerated could last longer than they do? This thought is not just an impossible dream. Scientists have been working on extending shelf life for years, and they're not about to give up now. Moreover, with the right handling of your food at home without a magic wand or some high-tech science--you can make changes in your food handling in ways that keep things  fresher longer. For safety and economy, it's well worth increasing shelf life.

Consider these statistics, quoted in the Chicago Tribune recently: About 40% of all food produced in the U.S.-- including nearly 50% of all produce--winds up uneaten. About $218 billion  worth of unused food is thrown out from homes, grocery stores, and restaurants. Better packaging could enable the public to avoid  creating 72,000 tons of waste and 330,000 tons of greenhouse gas emission. We could also save 44 billion gallons of water a year.  


Let's look at companies and scientists working on solutions to food waste and see what two members of the Shelf Life Advice Advisory Board thinks of these efforts.  Then, let's conclude with some good advice for homemakers trying to keep what they buy and cook in safe and tasty condition for a bit longer than they have in the past.  Past articles on Shelf Life Advice  tell you how to somewhat control ethylene, using it to ripen some produce faster or slow down ripening, whichever serves  your needs at a particular time.


Food quality tends to deteriorate before it becomes dangerous to consume.  People throw out food because it may look, smell, or taste spoiled or because they fear eating it will cause illness.  Keeping both in mind, let's consider current research and recommendations regarding what to throw out versus what to serve for dinner. According to a recent Penn State press release, some 76 million cases of foodborne illness occur  in the U.S. every year, and these illnesses cause 300,000 hospitalizations and 5,000 deaths.


Creating Antimicrobial film to Protect Meat, Fish, and More


Dr. Catherine Cutter, a member of the Department of Food Science at Penn State University, also serves on the Shelf Life Advice Advisory Board. She called our attention to work that her research group has been doing on antimicrobial film.  When a visiting scholar, Abdelrahim Hassan "spearheaded" Cutter's group, the research took an important step forward. Hassan figured out how to fuse an antimicrobial layer to polyethylene plastic. He created a film made by bonding a clear polyethylene plastic (commonly used to vacuum-pack meat and fish) with an antimicrobial layer that was infused with  Lauric arginate, which could kill pathogens such as salmonella, listeria, and E.coli. The new film "significantly reduced foodborne pathogens on the experimentally inoculated surfaces of the raw and ready-to-eat muscle foods after refrigerated storage."


According to  Dr. Cutter, the findings will interest both the packaging and the muscle food industries as well as regulatory agencies striving to reduce pathogens in the food industry.  "Polyethylene exhibits many desirable properties, such as strength, transparency, gas permeability, and water resistance," she said. "The novel composite film can give us antimicrobial properties and at the same time provide the strength and all the other desirable properties of polyethylene that the industry is still looking for."


Cutter and her team of researchers will continue to study how this new film might affect the shelf life of various food products and how consumers might respond and accept this new film.  Penn State has applied for a provisional patent on its composite antimicrobial film.  

Controlling the Ripening of  Produce


For years, science and industry have experimented with ways to speed up or slow down the ripening of some types of produce by creating  controlled atmosphere environments. One example food scientist Dr. Karin Allen gave us: placing a load of apples in cold storage rooms and then flushing the room with ethylene to ripen the apples more quickly or with carbon  dioxide to slow ripening down. 


I remember that, several years ago, produce supermarket departments were  displaying for sale bags (green, I believe) that were supposed to delay ripening.  I tried them with bananas and never seemed to have much success. 


A newer approach, used by AgroFresh, Inc. and  Hazel Technologies, involves encapsulating Methycyclopdropene (1-MCP or a similar compound), inserting this  material in a sachet, and placing it in a package of climatic fruit (produce with class A respiration) such as apples, apricots, avocados, bananas, oranges, peaches, tomatoes, cherries, pears, broccoli, and others.  Food scientist Dr. Clair Hicks says, "The procedures that AgroFresh and Hazel use are not useful for other types of foods. However, there are other technologies that are quite effective for enhancing the shelf life of other foods."


A Hazel representative expressed great hope that the company's product could help consumers keep their produce from ripening too fast.  Here's the quote from a Chicago Tribune article on December 1, 2019 : "Envision, in the next 18 months or so, literally selling a banana box to consumers. You keep it on your  counter, put a (Hazel) sachet in there once a month, and you have bananas that last forever." Wow! When I bring home bananas that are ripe enough to eat immediately, they last for 2-3 days before turning  black outside and mushy inside. Dr. Allen doubts that Hazel's product will benefit consumers because, she explains, different types of fruit would need different refrigerator environments (perhaps different temperatures, different amounts of oxygen or carbon dioxide, or different amounts of humidity). No one has a room full of refrigerators to accommodate these different atmospheric needs. Will American homes be using Hazel sachets in the future? Maybe or maybe not. Time will tell.


Businesses that transport fruits for long distances or store them for long periods of time can  benefit most from using AgroFresh or Hazel's techniques. The two companies mentioned above have had litigation and mediation disputes over patent infringement rights to their similar processes.  


Keeping Leftovers Palatable and Healthy Some Low-tech Ways


Consumer Reports on Health, in its April 2020 issue, covers both safety and quality in its article entitled "7 Ways to Keep Leftovers Tasty--and Safe." We'll cover some of the suggestions in our own  words:


• Keep your refrigerator temperature at 37° F. rather than 40°. 


• The infamous "danger zone" for food (the temperatures between which bacteria can grow rapidly) is between 40°-140°F. Perishable food should be out of the fridge or the oven no longer than 2 hours.


• Refrigerate food in smaller containers.  One large pot of soup or chili or stew may take longer than 2 hours to get out of the danger zone  even if it's in the fridge for 2 hours.


• Use refrigerated leftovers within 3-4 days.  If you don't plan to eat them for several days, freeze them.


• Don't defrost frozen foods on your counter!  The food near the top surface will defrost faster than the food in the middle, and what defrosts faster may be reach the "danger zone" and become contaminated.


• Wrap your cooked, refrigerated leftovers tightly to prevent them from being degraded by moisture or oxygen. 


Understanding the Role of Ethylene in Ripening Produce


To learn more about  the effect of ethylene on produce and how to use this knowledge to encourage fruits and vegetables to ripen more quickly or slowly, go to the search bar ("name of food or topic") on the Shelf Life Advice home page, and type in "ethylene."  You'll find links to many articles on handling produce .  These two may have information you'll find especially useful: "Ethylene and Produce: Friends or Foes?" and "Six Tips for Extending the Shelf Life  of Foods."




Contributions from three members of the Shelf Life Advice Advisory Board:

Karin E. Allen, Ph.D. Utah State University, Dept. of Nutrition, Dietetics, and Food Sciences

Catherine Nettles Cutter, Ph.D., Pennsylvania State University, Department of Food Sciences

Clair L. Hicks, Ph.D., University of Kentucky, Dept. of Animal and Food Sciences


Penn State  News, University Park, PA:


"Novel composite antimicrobial film could take a bite our of foodborne illness" January 19, 2020.

Chicago Tribune: "No more brown bananas or squishy avocados?" December 1, 2019.




Consumer Reports on Health: "7 Ways to Keep Leftovers Tasty--and Safe" April 2020.



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