FAQs on Raw Fruits and Veggies—the Answers Can Protect Your Wallet and Your Health

MelonWe asked two food scientists to answer some FAQs about raw produce, with an emphasis upon melons, apples, and greens. Their answers can help you get produce ripe but not overripe; prevent spoilage and/or contamination; cut down on waste; and, as a result, save money.


Proper handling of produce is also extremely important to protect the health of your family and dinner guests.  Many people don’t realize that raw produce is a common cause of food-borne illness.   In an August, 2011 article, Consumer Reports points this out:  “In a study of more than 100,000 illnesses linked to food between 1990 and 2006, they [fruits and vegetables] caused more problem than poultry and beef combined.” The article also reminds consumers of the following: “While any produce eaten raw can carry bacteria, be particularly careful handling berries, cantaloupe, leafy greens, sprouts, and tomatoes.”


How should I handle whole melons?


Food scientist Karin Allen says, “Whole melons should not be refrigerated.  Generally, it is recommended to keep them at 50°F – 60°F, but some studies have shown that watermelon will suffer from chill injury even at 50°F (this is usually seen as pitting and loss of color).  However, the warmer your kitchen is, the faster the melons will ripen & spoil.”


After harvest, melons will not become sweeter, Dr. Allen explains, but they will develop a softer texture.  In some cases (for example, cantaloupe) this can be desirable, but in others (watermelon) it is not. 


She also points out that it’s important to wash the exterior of melons even though we don’t eat the rind.  “Pathogenic bacteria may be brought from the surface rind to the interior by the knife blade.  When left at room temperature, these bacteria will multiply rapidly, as will spoilage bacteria and mold.”


If I buy half a melon and then discover it’s too hard to eat, how can I ripen it?


You can’t. According to Dr. Allen, “If you purchase a cut melon, it is as ripe as it will ever be.”   Once it’s cut, it will not ripen further.  Also, a cut melon must be refrigerated to avoid the growth of spoilage and pathogenic bacteria, and fruits don’t ripen further once they’re refrigerated. This information suggests that buying half of a cantaloupe or honeydew melon may not be a good idea.  Don’t count on the store to cut them only when they’re ripe enough to enjoy.


After I’ve mistakenly refrigerated whole raw peaches that are still hard, can I put them back on the counter to ripen more?


Dr. LaBorde explains that peaches are cooled after harvest for shipping and storage.  They can be taken out of the refrigerator for ripening. 


How long can cut-up fruit be left out at room temperature?


Food scientist and produce expert Dr. Luke LaBorde emphatically states, “Two hours.”  Then they should be refrigerated.  And, he says, when serving these leftovers, “Don’t put them out for two hours again.”


Which fruits and vegetables can be ripened faster by putting them near other fruits or veggies?  Which fruits and vegetables aid ripening?


Fruits and vegetables that give off ethylene gas hasten the ripening of some other produce.  Those that respond to ethylene will ripen (and some may become moldy) faster in its presence.  Dr. Allen has provided us with this link, which contains a 3-page ethylene production/sensitivity chart that answers your questions.  Various types of produce (just about anything you’re likely to have in your kitchen) are identified with initials indicating how much ethylene they produce.  (For example, VH = very high; VL = very low.)  Fruits and veggies that are sensitive to ethylene actions (which are called “responders”) will ripen faster when exposed to ethylene.  Some types of produce are both producers and responders. 


You can use the information in the chart to your advantage to ripen produce that’s not ripe enough and also prevent produce from getting overripe (by keeping it away from high ethylene producers). Dr. Allen provides the following specific advice based upon the ethylene reaction: “Even at cool temperatures, the spoilage effects of ethylene continue.  I usually put citrus, vegetables, and berries in one bin, with apples and pears in the other.  Even better, find another cool storage area for apples and keep them out of the fridge completely.”


 “With the exception of watermelon, most melons (medium to high producers) produce enough ethylene that they don’t need to be held with apples (high to very high producers).  If the melon is very hard, it might benefit from being placed next to apples for a day or two, but it wouldn’t need to be in a paper bag.  Watermelon doesn’t produce a lot of ethylene, but it does respond to it.” Therefore, if your watermelon is ripe enough, don’t put it next to produce that produces a lot of ethylene. 


“Peaches, nectarines, and plums are all pretty good producers, and they’re high responders.  As long as they have not been cut, they can be left at room temperature to ripen.  I typically pick several with varying degrees of ripeness. The softest ones get eaten first, then the next softest, and so on.”


Are apple slices sold in small bags (for example, at Subway and McDonald’s) safe to eat?


It’s always ironic and unfortunate when efforts to make our food choices healthier lead to the opposite result. A Shelf Life Advice quick computer search turned up two recalls (due to pathogens) on commercially cut-up apples, one recall in 2009 and one in 2010. (There may have been more we didn’t catch.)This led us to ask: how risky is it to eat commercially sliced apples?


Generally, the more that food is handled before it reaches your home, the more likely it is to become contaminated somewhere along the food processing chain.  The packages of apples we looked at were treated with an antibrowning agent (citric acid and calcium) but nothing more. Are these a safe product?


Dr. LaBorde gave us this answer:  “The risk can be controlled if the people handling the product know what they’re doing.  If they use a slicing machine, how often is the machine cleaned? Any time you chop up something, creating more steps, the risk is increased.”  However, Dr. LaBorde expressed some confidence that major companies such as McDonalds, who are very eager to avoid the bad publicity associated with a recall on one of their products, make every effort to work out procedures that will result in a safe product.


With Dr. LaBorde’s reassurance in mind, three of us tried a Subway sliced apple packet (which are unpeeled) and a McDonald’s packet (which is peeled and comes with a caramel dipping sauce).  They tasted fine--firm and juicy--and did not make us sick.  Our advice: 1) these packets say “Keep refrigerated.” Don’t buy them if they’re not refrigerated in the store.  Also, if you bring them home, refrigerate.  Don’t put them in lunches brought to school or work and left unrefrigerated for more than two hours.  2) Pay attention to the “use by” date; they probably won’t taste good after that.


What type of wash should homemakers use to decrease the risk of consuming contaminated produce?


According to Dr. LaBorde, a commercial wash treatment or one that the consumer concocts is no better than cold running water. The number of microorganisms required to make someone sick is very low; a stronger wash isn’t going to kill all of them.  “Whatever you do in the home is too late,” he says. “There shouldn’t be any E. coli on the product in the first place.”  He urges consumers not to use bleach on their produce.  “That introduces chemical hazards that may outweigh the microbial hazards.”


Regarding greens, here’s Dr. LaBorde’s advice: 


- Whole lettuce:  Pull off the outer leaves and discard.  Wash under cold running water the part you’re planning to use that day.


- Bagged greens: No need to wash these; they’re prewashed. 


Is a bag of greens less likely or more likely to be contaminated than a whole head of lettuce?


On the one hand, there’s more risk of contamination from the additional handling.  However, the magazine First for Women quotes David Acheson, M.D. former associate commissioner of foods at the FDA, as follows:  “’Triple washed’ or ‘prewashed’ bagged salad used before its expiration date is likely safer than a loose head of lettuce, especially one that’s not properly cleaned.” The magazine says that big producers of prewashed greens use a new rinsing technology that removes much more E. coli than the traditional chlorine washes did. 




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


Luke LaBorde, Ph.D., Pennsylvania State University, Dept. of Food Science


fda.gov “Florida Company Recalls Sliced Apples”



fda.gov “Florida Company Recalls Sliced Apples”



engineeringtoolbox.com “Fruits and Vegetables - Optimal Storage Conditions”



Consumer Reports on Health “Surprising facts about food poisoning” August 2011.


First for Women “Keep Your Salads Safe from E. coli” 8/8/11.


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