More FAQs about Minimum Safe Cooking Temperatures: Pork and Other Perishables

If you've ever purchased a food thermometer (and I certainly hope you have), you probably found it packaged with a list of minimum safe temperatures for cooking different types of perishable foods.  For meat and fish, it's 145°F; for eggs, it's 160°F; for poultry, it's 165°F; and so on. Shelf Life Advice has also told you that leftovers should be heated to165°F. Perhaps you've been wondering why there's so much variation in recommended safe cooking temperatures. The following Q/As delve into the reasons.

Why are there different minimum safe temperatures for different foods?

Food scientist Dr. Catherine Cutter, a Shelf Life Advice Board member, points out that an intact piece of meat (one that hasn't been tenderized, needle-injected, or otherwise processed) is essentially sterile inside.  Therefore, the minimum safe cooking temperature can be lower than, for example, non-intact or ground meat.  Eggs need to be cooked thoroughly (to 160°F) because there's more surface area exposed to bacteria.  Chicken, Cutter explains, has a lot of "nooks and crannies." It needs to be cooked to a higher temperature (165°F) to kill the bacteria throughout.  It's important to check the temperature in different parts of a chicken because some parts take longer to reach a safe temperature. 

Dr. Timothy Bowser, a food process engineer and also an Advisory Board member for this site, says, "The temperature requirement to inactivate a microbe has a lot to do with the type of microbe expected, its growth state, and the physical properties of the food that it is living in--especially moisture content and pH (acidity). Often the best temperature is determined by experimentation. An added safety factor is normally included."

When asked what he meant by "growth state," Dr. Bowser provided this explanation: "A population of microbes undergoing stress of some sort may safeguard its existence by forming a protective structure called a spore. A spore is a dormant bacteria encased in a protective coating. Spores are much tougher than ordinary microbes and are difficult to kill (e.g., they require more heat). Spores come back to life when conditions become more favorable."

To reach a copy of the Shelf Life Advice chart on safe cooking temperatures, click here.  We suggest printing it and posting it on your fridge for convenient reference.

Why can't I leave a cooked perishable out of the fridge for more than 2 hours?  If I accidently leave such an item on the counter for several hours or even overnight, wouldn't reheating it to 165°F kill enough pathogens to make it safe to eat?

Dr. Bowser explains: "The heat will probably kill the pathogens, but if they left any toxins behind, there is a good chance that the heat will not inactivate the toxins. We must remember that many microbes produce dangerous toxins (e.g., tetanus toxin and mycotoxins)."

Dr. Joe Regenstein, a food scientist and another Shelf Life Advice Advisory Board member, gives us a similar answer:  "I’d worry about Staph Aureus from human handling; that produces a toxin that is not heat sensitive."

Related Shelf Life Advice articles you may want to read:

http://shelflifeadvice.com/content/i-left-it-out-too-long-can-i-still-eat-it

http://shelflifeadvice.com/content/faqs-reheating-food-pizza-chicken-and-everything-else 

Why has the recommended safe cooking time for pork been lowered from 160°F to 145°F?

Dr. Cutter explains that Americans used to cook pork to 160°F until it was no longer pink.  That was the recommended safe temperature. Then, in May of 2011, the U.S. Department of Agriculture's Food Safety Inspection Service (FSIS) announced a new guideline for cooking pork.  This stated that cooking pork to an internal temperature of 145°F was sufficient.

The reduced temperature recommendation is the result of improvements in safety. "Today's pork is much improved in terms of pathogens," says Cutter.   "Most pigs for human consumption are kept in a confined environment; they are no longer out in the fields eating whatever is available. Their controlled diet and environment greatly reduce the chances that people will contract a parasitic disease (for example, trichinae) caused by eating raw or undercooked pork." (Note: The new temperature guideline doesn't apply to meat from free-range pigs (those that are permitted to go outdoors on natural ground); this meat should still be cooked to 160°F.)  

Research funded by Pork Checkoff (a program that supports the National Pork Board with funds collected by the federal government) has put, on its official website, a study conducted by Texas A&M. It showed that, after being cooked, the meat would generally be given at least a 3-minute resting time, during which time the meat temperature in the center would continue to rise, and this heat is sufficient to kill the trichinosis parasite, which might be inside the meat.  Given this information, the FSIS agreed that the 145°F temperature would be safe. This new recommended procedure gives diners who follow it a slightly pink product that is not overcooked and is, therefore, tastier, juicier, and tenderer than when pork is cooked to 160°F.

The 145°F recommendation is now the same as the minimum safe cooking temperature for intact cuts of beef and lamb. Pork Checkoff says that this change applies to whole-muscle cuts of pork, such as loin, chops, and roasts.  "Ground pork, like all other ground meat, should be cooked to 160°F."

Why should all leftovers (even those that needed to be cooked only to 145°F) be reheated to 165°F?  And why shouldn't I reheat leftovers more than once?

Even when a food is cooked to 165°F, not all the bacteria in it are killed.  The few that remain can multiply rapidly when the food is not kept either hot or cold.  Every time perishable food is cooked or cooled, it passes through what food scientists call the "danger zone" (40-140°F), the temperature range at which bacteria grow rapidly.  When warm or hot leftovers are being cooled in the fridge, they pass through this zone, and then they pass through it again when they are being reheated. Food scientist Dr. Susan Brewer advises against putting food through this "danger zone" more than twice. She points out that the more food is reheated, the more toxins might build up, and these are not killed by the usual heating temperatures. A high bacteria count or toxins in food can cause food-borne illness, which can sometimes be quite serious or even fatal.

For a more detailed discussion of these points, click here:

http://shelflifeadvice.com/content/faqs-reheating-food-pizza-chicken-and-everything-else

Food scientists advise reheating all leftovers to 165°F for the reasons discussed above. 

Food scientist Dr. Karin Allen, a Shelf Life Advice Board member, provides a detailed explanation (in the link's "Side Dishes" section) about proper handling and reheating of casseroles, potatoes, and other starchy foods to avoid contamination with Staphylococcus aureus, commonly known as "staph." She also recommends reheating to 165°F.

Can I trust the "reheat" feature on my microwave oven to reheat my leftovers to a safe temperature?

Dr. Bowser recommends checking the temperature with a food thermometer a few times and in a few places (since microwave ovens don't heat food evenly).  If you find that the oven does, in fact, get your food to 165°F after you check a few times, then you can trust it to reheat same food and same quantity to the right temperature.  However, if it doesn't do the job, microwave the food a bit longer.  (Editor's note: My microwave seems to heat leftovers longer and hotter than necessary, which, in some instances, has been somewhat hard on quality.  I often reheat with 50% power and then check the temperature with a thermometer.)

Dr. Regenstein says the the rotating plate in the microwave moves the product in circles but not to a new position. You need to be sure that the center of your food is actually heated to165°F.  "Microwave heating can, occasionally, be a real challenge," Regenstein tells us. I've discovered that, too.

After I've cooked food to the proper temperature for a party, what temperature must I hold it at to keep the food on a buffet safe?

To keep food out of the danger zone, put cooked perishables on hot plates that can hold the temperature at 140°F (or warmer). 

By the way, if you plan to reheat your leftovers and want to be sure they'll be safe to eat, be careful about how you handle the food after your party. If you have a large quantity of soup, casserole, etc. left over, before refrigerating, place the container of hot food into an ice bath.  That will get the contents out of the "danger zone" faster. 

Another alternative is to put large amounts of hot food into smaller, chilled containers before refrigerating. A large pot of hot food can take a long time to cool, and the fridge may not be able to get it below 40°F within the required 2 hours.  The goal is to get perishable food (hot food and cold) out of the "danger zone" within that time period.  For details on how to use an ice bath and other ideas for rapid cooling, click here.

Source(s):

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

Susan Brewer, Ph.D.  University of Illinois, Department of Food Science and Human Nutrition

pork.org  (pork checkoff.)  "New USDA Guidelines Lower Pork Cooking Temperature"

http://www.pork.org/News/1208/NewUSDAGuidelinesLowerPorkCookingTemperature.aspx#.UH7iKbRQ0yE