- Meat and Poultry
- Fish and Shellfish
- Cream and Cream Products
- Eggs and Egg Whites
- Ice Cream
- Dairy Spreads
- Fruit, Fruit Products
- Sauces, Dressing, and Dips
- Condiments, Herbs & Spices, Spreads
- Ingredients for Cooking
- Prepared Foods
- Bakery Goods and Sweets
- Grains, Pasta, and Cereal
- FAQs on Bacteria
- What are bacteria?
- How can I avoid getting sick from a bacterial illness?
- How dangerous is a staph infection?
- Can I assume that if food smells bad its unsafe to eat and if it smells ok that it is safe to eat?
- How dangerous is botulism?
- How dangerous is listeria?
- How many types of bacteria are there?
- What foods are likely to be contaminated by listeria?
- What foods can give a person a staph infection?
- What foods can give a person botulism?
- Why do some bacteria make people sick?
- Why does refrigeration keep bacteria from multiplying?
- Can I avoid all contact with bacteria if I’m careful?
- How Many Bacteria Does It Take to Cause Illness?
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- Are Ceramic and Enamel Cookware Safe and Practical?
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- What Brands of Cookware are Recommended by Experts?
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- Exactly what is meant by the phrase perishable food?
- Defining Some Current Language about Food
- What Does the Word “Foodie” Mean? It Depends Who(m) You Ask
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- What does the term shelf life mean?
- What's in Our Food? Maybe Processing Aids, Maybe not
- “Fresh,” “Natural,” “Processed”—What Do These Words Mean?
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- Exactly what defines a farmers’ market?
- Farmers' Markets: Why They're So Popular; How to Find One Near Your Home
- How should I handle produce at home?
- What foods are sold with restrictions at a farmers’ market?
- What should I bring to the farmers’ market?
- What shouldn’t I do or eat at a farmers’ market?
- What signs indicate a sanitary farmers’ market?
- What time of day is it best to go to a farmers’ market?
- FAQs on Food-borne Illness and Mishandling of Food
- About how many cases of food-borne illness occur in the U.S. each year?
- Answer Key to “How Much Do You Know about Safe Handling of Food?”
- How Much Do You Know about Safe Handling of Food?
- I Left It Out Too Long! Can I Still Eat It?
- Should Your Grocery Card Track Food-Borne Illnesses?
- Sudden, Awful Intestinal Distress--Is it the Flu or a Foodborne Illness--or Both?
- What YOU Can Do to Avoid Food-borne Illness
- What does the phrase food-borne illness refer to?
- FAQs on Food Product Dating
- Are stores required, by law, to remove outdated items from their shelves?
- Do most consumers actually pay attention to the dating on foods?
- Does the “use by” date matter once the product is frozen?
- Is information on food longevity and safety available by phone?
- What are expiration dates?
- What do the terms closed dating and open dating mean?
- What if there is no date on a product, and I don’t remember if I bought it a month ago or ten years ago?
- What should consumers know about food product dating?
- When Did You Buy It? When Did You Open It?
- When to Throw Food Out? Not on the Use-By Date
- Who establishes these product dates?
- Who requires and regulates dating on foods?
- Why do “best by” and “use by” dates sometimes seem conservative?
- FAQs on Food Safety
- "Is It Safe To….?" FAQs Answered by our Advisory Board
- FAQs about Ground Beef, Seasonings, Olive Oil, Lemon Wedges, and Fish
- FAQs about Mushrooms: Are they Very Dirty or Very Clean?
- FAQs about Soft Cheeses--What's Safe, What Isn't
- FAQs on BPA: the attacks continue, but are they justified?
- FAQs on Food Safety and Nutrition
- FAQs on Raw Fruits and Veggies—the Answers Can Protect Your Wallet and Your Health
- FAQs: Cutting Boards and Kitchen Counters--Selection and Care
- Food Bars/Buffets in Supermarkets--Is the food safe? How can you tell?
- Food/Meat Thermometers—What You Need to Know
- How Long Should Cheese Be Aged? Will the Rules Be Changed?
- How Long Will They REALLY Last? Part I: Non-perishables
- How Long Will They REALLY last? Part II: Perishables
- Imported Foods—What’s Safe, What’s Risky?
- Is It Safe? Is It Nutritious? More Survey Answers from Scientists
- Is It Time to Switch to Pasteurized Eggs?
- Is the Food Safety Modernization Act Making Our Food Supply Safer?
- More FAQs about Minimum Safe Cooking Temperatures: Pork and Other Perishables
- Sushi: Why Such a Short Shelf Life?
- Winter Food Storage—Can I leave It in the Car or in the Garage?
- Would You—Should You—Do You--Eat Irradiated Food?
- FAQs on Food Wrapping
- Are any plastic wraps or containers really “microwave safe”?
- Are some plastic wraps more effective than others?
- Can I refrigerate meat and poultry in its store wrapping?
- Can I use plastic freezer bags to store produce in the fridge?
- Can chemicals leach unto food from plastic wrap or containers?
- Do coated plastic bags really help produce last longer?
- Does aluminum foil give foods a metallic taste?
- Does exposure to aluminum cause Alzheimer’s disease?
- Everything You Need to Know about Wrapping Food Right
- How should fruits be wrapped before refrigeration?
- Is it safe to use aluminum foil in a microwave oven?
- Should I wrap raw vegetables loosely or tightly before refrigerating?
- What are some advantages and disadvantages of aluminum foil?
- What produce needs to be wrapped before refrigerating?
- What’s better for wrapping food—plastic or aluminum foil?
- Why does foil sometimes darken, discolor, and leave black specks on food?
- Will a foil cover help keep foods on the table hot or cold?
- FAQs on Freezing Food
- FAQs on Leftovers
- FAQs on Mold
- What is mold?
- Does mold ever grow on nonperishable food?
- Can I remove a moldy part from food and eat the rest?
- About how many different kinds of molds are there?
- How can I avoid getting mold on my refrigerated food?
- Is mold always visible?
- Are any molds harmless?
- What food groups are most susceptible to mold?
- What kinds of illnesses can result from eating moldy food?
- What kind of packaging protects foods from mold?
- What other safety tips will help prevent mold from growing?
- Why are some molds dangerous?
- FAQs on Organic Food
- What Is Organic Food?
- Are Organic Methods More Humane to Animals?
- Does Conventional Food Have a Longer Shelf Life Than Organic?
- Does Organic Food Taste Better than Conventional Food?
- Is Organic Food More Nutritious Than Conventional Food?
- Is Organically Grown Food Better for the Environment?
- What Do the Various Organic Labels Mean?
- What Important Contributions Has the Organic Movement Made?
- Which Are Safer: Organic or Conventional Food Products?
- Will Organic Baby Food Make Baby Healthier?
- FAQs on Oxidation: How It Affects Foods
- FAQs about Plastic Products Used with Food
- Pyrex® Glassware: Is it safe to use?
- Are plastic bags safe to use in the microwave?
- Are some plastic wraps safer and/or more effective than others?
- Are there any health risks from reusing plastic water bottles by refilling them with tap water?
- Are we eating chemicals from plastics along with our food?
- Can I microwave food in my plastic containers?
- Does the plastic used in water bottles pose a health risk?
- If I heat food in an open can, will that cause the plastic lining to leach chemicals into the food?
- Is it safe to heat frozen entrées in their plastic containers and with their plastic wrap?
- Is it safe to use plastic wrap as a covering when microwaving food?
- Is it safe to wash and dry plastic plates, cups, containers, and utensils in the dishwasher?
- Is there good evidence that BPA is harmful to human health?
- Of the plastic products used to store, heat, or eat with (wraps, bags, containers, silverware, plates, etc.), which contain BPA?
- What is BPA?
- Why is so much of today’s food packaged in plastic?
- FAQs on Preservatives
- What are Preservatives?
- All things considered, is our food supply safer or less safe because of preservatives?
- Are the preservatives in hot dogs and similar products health risks?
- What preservatives are known to cause allergic reactions?
- What are some common preservatives used in food?
- What food groups commonly have preservatives in them?
- Why are preservatives added to food?
- Will the label on the product tell me if it contains a preservative?
- FAQs on Washing Produce: Why and How
- Other FAQs
- Can chicken soup really cure a cold?
- Is Chocolate Good For You?
- Can Science and Technology Help You Save Food Dollars?
- FAQs Answered By Our Board Scientists: on Chickens, Bananas, Old Salad Dressing, and More
- FAQs about Food Price Increases
- FAQs about Products We Use with Food
- FAQs about Shelf Life: Tortillas, Pancakes, Wine, and More
- Food Fraud: Are you paying for scallops and getting shark meat?
- Is Cheese Addictive? Only If You Eat It
- Missing Chickens: Where Have All the Small Ones Gone?
- Nine FAQs about Food Labels
- Quiz Yourself! Check Your Knowledge about Food Temperatures
- Scientists Answer Two FAQs about Egg Safety
- Should Sour Cream and Cottage Cheese Be Stored Upside Down?
- Some Shelf Life Info, General and Specific (Spirits, Defrosted Veggies, Green Tea, and More)
- Syrup from a Tree or from a Lab--Which Should You Pour on Your Pancakes?
- Ten FAQs about the Prickly Pineapple
- What's New in Food? IFT Expo Offers Tasty Innovations
- What's on the Menu in Cuba?
- What’s in My Water? Answers to FAQs
- What will you be dining on this year? Here are predictions from folks in the know
- FAQs on Bacteria
- Books: Food for Thought
- Food Safety
- It Says "Use By Tomorrow," But You Don't Have To
- Ten Tips for Consumer Food Safety
- Food Allergies: Recognizing and Controlling Them
- “Is It Spoiled?” When in Doubt, Check It Out
- How To Keep Your Cooler Cool
- Recent Recalls: Salmonella Threatens 100s of Products
- STOP! Don’t Rinse That Raw Chicken!
- Sous Vide—A Better Way to Cook?
- Why You Need a Safe Cooking Temperature Chart and How to Get One Right Now
- “Myth-information” about Food Safety: You’d Better Not Believe It
- After The Storm: What You Can Save and What You Must Throw Out
- How to Protect Your Food During a Power Outage
- Meet Your Beef--Via Bar Code Info
- Organic Food, GMOs, the Safety of American Food, the Value of Use-By Dates, and More--Scientists Tell Us What They Think
- Raw chicken, Leftovers, Deli Meats, and More-- What Surveyed Scientists Said
- Tips About 4 Popular Beverages: Wine, Coffee, Water, and Soda
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- Produce: Handling Tips
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- A Novel Method for Cooking a Turkey
- Crock Pot Cooking Tips for that Ideal Winter Dinner
- Cucumbers: for Cool--and "Cool"--Summer Treats
- Going Away for All or Part of the Winter? Prepare Your Kitchen for your Absence
- How To Grill Safely During the Summer
- How do summer squash and winter squash differ?
- New Year’s Resolutions For a Safer Kitchen
- Preserve the Taste of Summer by Canning—But Do It Safely
- Summer Food Fests Offer Much More than Calories
- Summer Party Tips: Baby Carrots (Using for Dips) Hot Dogs (Ditching the Guilt), and Watermelon (Finding a Ripe One)
- Tailgating: How to Do It Right
- Tips on Keeping Your Summer Fruits Flavorful and Healthy
- Shelf Life Tips
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- Battling the Ripening of Bananas
- Food Preservation--Low-tech Past, High-Tech Present and Future
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- Shelf Life of Foods: What You Need to Know
- Shellfish and Shelf Life Aid from the Canadian Maritime Provinces
- Tips for Carry-along Lunches for Work and School
- Tips for Freezing Food and Freezer Care
- Cooking Frozen Foods
- Freezers And Food Safety
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- Freezers And Nutrient Retention
- How Often Should You Defrost And Clean Your Freezer?
- How To Defrost And Clean Your Freezer
- How To Defrost Frozen Foods
- How To Freeze Foods: The Quicker The Better
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- Refreezing Frozen Foods
- What You Can Freeze And What You Can't--Or Shouldn't
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- Answers to Questions about Thanksgiving Dinner
- Chocolate Is Even More Healthful Than You Thought
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Raw chicken, Leftovers, Deli Meats, and More-- What Surveyed Scientists Said
PART 1 OF A 3-PART SERIES
During the fall of 2013, Shelf Life Advice embarked upon an ambitious project: We emailed a survey to more than 800 scientists who teach and/or do research and are on the faculty of approved* food science programs. Faculty members from more than a dozen colleges or universities responded to our questions about food safety, nutrition, and controversial food issues. Some of their answers may influence how you grocery shop and handle food in your kitchen.
Conducting this survey taught us two things about asking scientists questions related to their area of specialization: 1) It seems that great minds do not think alike. Our survey results rarely showed consensus. 2) Ask a scientist a seemingly black-and-white question, and the response is often gray. It's likely to begin with "It depends." Fortunately, our survey provided ample space for comments, many of which are included in the report below. These should help readers to see the complexity of these scientific matters and to explain why there isn't total consensus.
Part 1 of this report, covers 7 Yes/No questions dealing with food safety. Part 2 includes 6 multiple choice items and one Yes/No item about both food safety and nutrition. Part 3 deals 6 Q/As about important issues related, for example, to organic food, GMOs, and the relative safety of the U.S. food supply. All three parts should be on the Shelf Life Advice home page by the end of January.
The Yes/No questions on the survey gave our 35 respondents the options of answering "Don't know" or "Don't choose to answer." Therefore, percentage totals on the Yes/No answers rarely add up to 100%.
Some respondents' comments are quoted or paraphrased following the percentages on the answers. These include comments from some of our site's Advisory Board members.
Are deli meats and cheeses that are sliced and wrapped at a store's deli counter more likely to be contaminated than the same type of products sold in sealed packages?
Yes: 78% No: 9%
Some reasons for the "yes" answers from respondents:
- The slicer [the equipment] and the food handler could both be a source of microbial contamination. ("Deli slicers are notorious for spreading contamination.")
- "Many packaged sliced deli meats now receive a post-packaging pasteurization process, but not all."
Should raw chicken be rinsed with tap water before preparing it for cooking?
Yes: 19% No: 74%
Comments from survey respondents:
- "Bacteria in the chicken juice could be spread to food contact surfaces around the kitchen." (Fear of contaminating sinks, sponges, counter-tops, etc. and thereby spreading pathogens to other foods is the concern.)
- "Let heating be the safety insurance."
- "It does not have to be rinsed, but rinsing will not hurt."
- "Contamination can splash onto other things in the kitchen. But I rinse it anyway to be sure there are not funny smells."
NOTE: For many years, the USDA has been advising consumers not to rinse raw chicken.
Is it better to wash produce before refrigerating it rather than waiting to wash it until immediately before cooking, serving, or consuming it?
Yes: 26% No: 68%
Comments from survey respondents:
- "Washing it can spread soil and germs around and get them into vulnerable sites on the produce. Also, unless the produce is carefully dried, washing can promote bacterial growth by leaving droplets of water on the produce."
- "If the purpose of washing is to remove microbial pathogens, then it likely doesn't matter when it's washed; at either point, washing isn't an effective means of eliminating microbial pathogens. However, if the question relates to produce directly from a garden, then washing before refrigerating is warranted to remove dirt, etc."
Shelf Life Advice advises consumers not to wash fresh produce until it's about to be used. (See "Guide to the Proper Handling of Fresh Vegetables.")
Is there a health risk in reheating the same leftovers a second time (assuming they're reheated to 165°F)?
Yes: 44 % No: 44%
Comments from survey respondents:
- Some respondents stated that it was safe to do this if the food was kept properly refrigerated between reheatings.
- Cooked, perishable leftovers should be reheated to 165°F within 2 hours.
- Most pathogens are killed at 165°F, but, if the food was not properly refrigerated, and staph toxin grew in it, these could survive the heating process and cause illness. Because of this danger, it's best not to reheat cooked food more than once.
Comments from Shelf Life Advice Advisory Board members:
Food scientist Karin Allen provides a detailed explanation of why she believes repeated reheating of food is risky in the Shelf Life Advice article "Reheating Food: Pizza, Chicken, and Everything Else." Her comments include this point: Every reheating puts food through the "danger zone" of 40° - 140°F, the temperature at which bacteria multiply rapidly, and some bacteria "offspring" may be more resistant to heat.
Food scientist Joe Regenstein adds: If food is heated, served, and put back in the refrigerator while still above 140°F, then it should be safe regardless of the number of reheatings. If left out on a buffet with time in the danger zone, then it should be reheated only if it was in the danger zone less than 2 hours.
Is it safe to refreeze refrigerated food after it's been totally defrosted for a day?
Yes: 52% No: 39%
Comments from survey respondents:
- It must be defrosted in the refrigerator.
- The quality of the refrozen food will have deteriorated.
- Both spoilage and pathogenic bacteria could grow if food is defrosted at room temperature. Freezing kills some but not many bacteria.
Shelf Life Advice agrees with the majority. See "Refreezing Frozen Foods."
If packaged, cut-up salad ingredients aren't slimy or brown around the edges, are they still safe to eat 2-3 days past the use-by date? (Assume they were not contaminated when purchased.)
Yes: 73% No: 10%
Comments from survey respondents:
- "I would use them for preparing a cooked dish, not for eating raw."
- "Assuming they were not contaminated when purchased, then yes, it would likely be safe. However, there is no way for the consumer to visually tell whether or not products are contaminated at purchase, so, as a general rule, I would not advise consumers to use packaged salads after the use-by date (especially vulnerable populations--such as the elderly or immunocompromised)."
If a baby is put to bed with a bottle of milk (not formula or breast milk) and he/she finishes the contents the next morning, is there a risk that this "old" milk will make the baby sick?
Yes: 69% No: 13%
Comments from survey respondents:
- If the milk was pasteurized, properly handled, and not long past the use-by date, it has a low chance of creating sickness. ("Use-by dates have quite a bit of wiggle room.")
- "It's possible that microbes present or introduced could grow during this period. Assuming the bottle is left unrefrigerated all night, then, yes, there is a risk."
- "You should not leave milk at room temperature for more than 4 hours."
- "It's a terrible practice that contributes to ear and respiratory infections, tooth decay, and 'nursing bottle mouth'" [a syndrome involving rapid decay of baby teeth in infants and children from long, frequent exposure to liquids that contain a lot of sugar].
Comments from Shelf Life Advice Advisory Board members:
From Joe Regenstein, Ph.D., Cornell University, Dept. of Food Science:
"Given that the milk was pasteurized, the odds of pathogens being present are low. But if the handling is sloppy, and someone introduces a pathogen, then pathogens could grow. However, normally pathogens do not compete well with spoilage organisms."
From Catherine N. Cutter, Ph.D., Pennsylvania State University, Dept. of Food Science:
"The milk should not make the baby sick if it was pasteurized. However, I would caution against this practice since the milk sugars (lactose) would remain in the baby’s mouth overnight. Bacteria in the mouth can utilize the lactose as a carbohydrate source, produce acid, and cause cavities.
"According to the following website: http://www.webmd.com/oral-health/guide/what-is-baby-bottle-tooth-decay, 'Never allow your child to fall asleep with a bottle containing anything but water.'”
From Timothy J. Bowser, Ph.D., Oklahoma State University, Dept. of Biosystems and Agricultural Engineering:
"Pasteurized does not mean microbe-free. Milk is one of the best mediums for microbial growth. Microbes in the milk will grow quickly (exponentially) at room temperature and could potentially threaten the health of the baby. I do not recommend the practice of putting a baby to bed with a bottle of milk that is left until the next morning."
Our question asked if there was a risk of illness but not how great a risk we were asking about. Perhaps that explains why the majority answered "yes" even though most scientists' comments indicate that the risk is minimal.
* The scientists contacted for this survey are all faculty members of North American college or university departments related to the food sciences. Their programs are on the "approved" list of the Institute of Food Technologists (IFT).
To read Parts 2 and 3 on our survey results, click on the following titles:
ShelfLifeAdvice.com survey, completed December 31, 2013.
Shelf Life Advice Advisory Board members who contributed to this article:
Karin E. Allen, Ph.D., Utah State University, Dept. of Nutrition, Dietetics, and Food Sciences
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