FAQs on Food Safety and Nutrition

berriesSince Shelf Life Advice emphasizes ways to prevent food contamination and postpone spoilage, it's not surprising that most questions the website or its editor receives are about proper food handling.  We're also asked about nutrition and shelf life.  Below, you'll find some recent questions that have come our way; they're answered by scientists who are members of the Shelf Life Advice Advisory Board.  


If I find one or two moldy pieces of fruit in a box of berries or a bag of grapes, to avoid risking illness, should I throw out the entire box or bag?


Food  scientist Dr. Catherine Cutter gives this advice:  "If the mold isn’t throughout the package, throw out the moldy ones and others that might be touching or in close proximity, wash the others in the package immediately, dry them well (so that more mold doesn't grow), and eat them as soon as possible."


Which vegetables and juices have more nutrients--fresh or frozen ones?


Contrary to popular opinion, in general, frozen produce is likely to have more nutrients than fresh produce, according to food scientist Dr. Karin Allen.  She explains why: although just-harvested produce may start out with the most nutrients, while traveling to the store and sitting around in the store, fruits and vegetables lose nutrients.  On the other hand, frozen produce was usually processed very soon after being harvested. Processing plants tend to be located very close to the farms where the produce to be frozen was grown.


Dr. Allen says that this message has reached many consumers in connection with solid foods, but most people still believe that fresh orange juice is better than the frozen concentrate.  That was true when it was necessary to boil the juice in order to concentrate it.  But now there's no need to do that.  "The juice is run through a tube which causes the water to freeze. The ice crystals are pulled out, and what remains is the concentrate.  There is no heat involved in creating orange juice concentrate, so nutrients are not destroyed."


If my electricity goes off overnight, is it still safe to use the raw steak that was in it?


Food process engineer Dr. Timothy Bowser replies: "Take the temperature of the steak using a clean thermometer. If it's above 40° F, then pitch it. The pathogens that might grow on the steak can be killed by heating, but the poisons they could have left behind may still remain. It’s not worth the risk."


How long should I keep a jar of marinated artichokes after I've opened it?


Use it within 2-4 weeks, says Dr. Cutter.  The open jar should be stored in the refrigerator.


Are use-by dates just a scam designed to get consumers to throw out good food and buy more? Don't canned goods remain safe and tasty long after their use-by date?


Dr. Cutter does not believe that these dates are a scam.  She makes 3 points:


 1)  The use-by date represents the window of time in which the product is at its peak in terms of quality.  (These dates are not about safety.) Peaches that were canned a year ago may taste fine to most consumers, but they may not be as tasty as those canned yesterday.  [However, Dr. Regenstein says, "Sitting in the juice makes the product better. Many cans are not released until they hit an equilibrium."


2) Manufacturers may not have tested the quality of a particular product beyond a year, so they may not know exactly when the item will begin to deteriorate. 


3) How the food is handled at home by the consumer affects shelf life.  [Examples:  Milk left out at room temperature for a half hour at every breakfast will begin to taste bad faster than milk promptly refrigerated. Canned goods stored in a hot area will not hold up as long as those stored in a cooler space.] 


To prevent foodborne illness, how often do I need to run the dishwasher to wash dirty dishes?  I live alone, and it takes days for me to get a full dishwasher load.


Here's Dr. Bowser's advice:  "Dishwashers full of dirty utensils and liquid and solid food particles can be ideal breeding grounds for bacteria, some of which may be pathogenic. It’s a good idea to run the dishwasher to remove food particles before major bacterial growth takes place. Bacteria grow exponentially, so I prefer to run the dish washer daily." 


Food scientist Dr. Joe Regenstein suggests this novel idea: if you have just a few dirty dishes, wash them by hand.  This conserves energy--maybe not yours, but the environment's.


Why are consumers given information about the country of origin of our food? Is this a safety issue? Should we avoid food from certain countries? 


"It is a way for consumers to have a choice," says Dr. Cutter.  "If they're afraid of contamination of food from a particular country, they can avoid it." 


Country of Origin Labeling (COOL) is a law that requires this labeling on many imported edible products. Retailers (such as full-line grocery stores, supermarkets, and club warehouse stores) must inform their customers regarding the source of certain foods. Food products covered by this law include muscle cut and ground meats of beef, veal, pork, lamb, goat, and chicken; wild and farm-raised fish and shellfish; fresh and frozen fruits and vegetables; peanuts, pecans, and macadamia nuts; and ginseng.


The whole matter of COOL gets confusing, Dr. Cutter points out, when a product is produced in one country and processed in another.  She gives this example: beef from cattle raised in Canada, which is then processed in the U.S.

Dr. Regenstein points out that this type of labeling can sometimes be more motivated by trade considerations than the actual needs of customers.


Two related questions:


 1) Let's say I'm broiling a lamb chop, and I stick my food thermometer into it to test for doneness. I get a reading of 130°F, not high enough to be safe to eat.  Can I use the thermometer to test the chop again without washing it between uses?


2) If I'm broiling a steak, and I use a fork to turn it over, can I use this same utensil to remove the steak from the oven when it's done? 


Dr. Bowser: "No! Please don’t ever do this. The partially-cooked food may still have live bacteria on or in it. The bacteria can be picked up by the utensil where it may survive and transfer to the fully cooked product if it is handled using the same utensil."


Dr. Cutter:  "The used thermometer or fork may spread contamination.  Moreover, if there's 'gunk' on the thermometer, you may not get an accurate reading.  Utensils can be quickly sanitized with alcohol strips and then rinsed."   


Dr. Regenstein: "The whole point of doneness is that it kills pathogens, including those on the surface of the thermometer. However, if the thermometer is dirty, I would probably wipe it off before a second use." Dr. Regenstein applies the same logic to the fork question and says the same fork could be used at the end of the cooking process as was used before the steak was done.  However, he suggests, "If you are concerned about contamination, leave the fork in the fire for a few seconds before using it."


Conclusion: Even scientists are not always in exact agreement as to what the "right" answer is. 


Question for the reader: Here's what I do: I run the thermometer prong under hot water before reusing it and take a clean fork to remove the steak.  How do you deal with these frequent cooking tasks?  We welcome your comments.





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



Timothy J. Bowser, Ph.D. , Oklahoma State University, Dept. of Biosystems and Agricultural Engineering


Catherine N. Cutter, Ph.D., Pennsylvania State University, Dept. of Food Science


Joe Regenstein, Ph.D., Cornell University, Dept. of Food Science


ams.usda.gov Agricultural Marketing Service (AMS) "Country of Origin Labeling"



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