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Cook Foods Adequately

Cooking is an essential part of making foods safe to eat since foodborne pathogens are killed when food is heated to 160°F for a few seconds or to a lower temperature for a longer period of time. The best way to be certain that food has been cooked to the proper temperature is to check it with a thermometer, preferably a digital thermometer.

It is risky to eat rare meats or poultry, raw or lightly cooked fish and shellfish, raw milk, and foods made with raw or lightly cooked eggs. Many pathogens live naturally in the intestinal tracts of food animals - Salmonella and Campylobacter for example. Surveys of meat sold in retail food stores indicate that between and of all meat and poultry cuts sold in 1999 may have been contaminated with one or more of these pathogens.

Ground meats are contaminated with pathogens throughout the meat but roasts and steaks usually only have pathogens on the surface of the meat. That's why it is important to cook ground meat until the temperature is 160 degrees on the inside, not just the outside.

A whole piece of meat such as steak or roast is not likely to contain bacteria. However, parasites such as Toxoplasma or Trichinella may be in the muscle of some animals, particularly pigs. Thus, it is advised to eat pork only when it is thoroughly cooked. Rare beef steaks and roasts are much less risky than rare pork or undercooked ground meat.

Wild game may have a high level of bacteria because of the difficulty of handling game in the field and thorough cooking of all cuts is recommended. ("Big Game from Hunt to Home, PNW 517, has information about field-dressing game.)

Salmonella sometimes contaminate the inside of the egg as well as on the eggshell (about 1 egg out of every 10,000 contains Salmonella inside the shell.)

Shellfish may pick up bacteria and viruses from contaminated waters. Fish may contain parasitic worms and Listeria bacteria. These microorganisms can then infect anyone who eats the shellfish or fish without cooking it properly.

At 160°F, most pathogens are killed very quickly. Any foods that are likely to be contaminated with pathogens should be heated to 160°F. Check the temperature with a thermometer to be certain that the food is fully cooked. Foods that should be cooked until they are 160°F include:

  • Ground meats (including turkey and chicken). (People usually judge whether ground meats are cooked by checking to see if the meat is brown. Using visual signs to determine that meat is done is risky because it has been shown that hamburgers may appear brown before they reach 160 degrees F or remain pink after reaching 160°.)
  • Pork and game meats.
  • Poultry. (When poultry is cooked to 160 degrees F, the meat may not look and taste cooked, although pathogens will be killed. At 170 degrees F, most poultry has the flavor, texture, or appearance associated with fully cooked chicken or turkey.)
  • Eggs. Either check the temperature with a thermometer or else cook eggs until both the yolk and white are firm. (This is one place where visual cues DO work well since the pathogens will be killed if the yolk and white are cooked enough to be firm.) If you use recipes in which eggs are only partially cooked or remain raw, use pasteurized eggs or modified recipes. The latter are available from the American Egg Board,http://aeb.org
  • Casseroles and other dishes containing eggs or raw meat.

Other temperatures to remember:

  • Cook steaks and roasts to at least 145 degrees F and until all the exterior surface appears to be cooked.
  • Cook fish and shellfish to 145 degrees F. Visual cues are commonly used to determine if fish and shellfish are thoroughly cooked. Cook fish until it flakes and loses its translucent or raw appearance and cook shellfish until the shell opens and the flesh is fully cooked. You should be aware, however, that little research has been done to identify the cooking temperatures required to kill pathogens on fish and shellfish, and that the cooking recommendations are based more on quality of the cooked product rather than on actual scientific data.
  • Re-heat leftovers to 165 degrees F to kill pathogens that may have survived the first cooking or that were introduced after cooking. (However Staph toxin won't be destroyed by the heating of leftovers.)
  • Pregnant women, the elderly and those with compromised immune systems should reheat hot dogs and deli meats before eating. Because these items have been fully cooked previously, they, like leftovers, should be heated to 165 degrees F.

USING THERMOMETERS: The only way to be sure your food has cooked to a safe temperature inside and out is to measure the temperature with a clean thermometer. The best kind of thermometer to use is a digital thermometer. It's quick, and its temperature sensor is in its tip so it can be used in both thick and thin foods. Even though the temperature sensor is in the tip, the tip still must be inserted at least inch deep into the food. And even though it's quick, it'll still take about 10 seconds for it to register the correct temperature.

You should test the middle of the thickest part of what you're cooking, because the center of the food is usually cooler than the outer surface. When you're testing a hamburger for temperature, lift it out of the pan on a spatula and insert the thermometer in from the side. That's because even if the patty is thick, it's easy to push the thermometer too far down and be beyond the center.

If you can't find a digital thermometer, you can still use one of the readily available bimetallic coil thermometers, which you can recognize because of their dial gauge. But you need to know that these thermometers read the temperature along a full two to three inches of the stem, up to the dimple that's in the stem. That means that the entire part of the stem from the dimple to the tip must be inside the food. For thin foods, it must be inserted sideways, as for the hamburger above.

Use your thermometer to test for doneness near the end of the cooking time. Most are not designed to be left in the food during cooking.

Making sure your thermometer is accurate: Some thermometers can be calibrated for accuracy. If yours can, follow the directions that come with it. But if it can't, you can still check it for accuracy. Test it in boiling water. It should read 212 degrees F if you live at sea level. (If you live at elevations higher than sea level, determine your elevation and check a reference book to determine the temperature of boiling water at that elevation.) For information on thermometers and their use, check outwww.fsis.usda.gov/thermy

Cook Foods Adequately
Adequate pasteurization, cooking or reheating is the primary control mechanism for pathogens introduced either before cooking or after the initial cooking stage.
  1. Use a thermometer to make sure that meat and poultry (including ground) are cooked to safe temperatures.
  2. Cook shellfish until the shell opens and the flesh is fully cooked; cook fish until flesh is opaque and flakes easily with a fork.
  3. If pregnant, immunocompromised, or elderly, heat hot dog and lunch meats to steaming hot or 165°F before eating.
  4. Use a thermometer to make sure that leftovers are reheated to 165°F.
  5. Cook eggs until both the yolk and white are firm.
  6. Use a thermometer to make sure that foods containing eggs are cooked to 160°F.



Frequently Asked Questions
  • Do leftover foods need to be thoroughly reheated?
  • How can I tell when eggs are cooked?
  • How do I know when food is adequately cooked?
  • What about fish and shellfish?
  • What foods do I need to be careful to cook thoroughly?
  • What temperature is needed to kill bacteria in meats and poultry?
  • Why are some people advised to re-heat lunch meats and hot dogs before eating them?
  • Why doesn't chicken look done when it is cooked to 160°?
  • Why isn't color a good way to tell whether ground beef is cooked?


    Links to Fact sheets
  • Preparation Of Apple Cider For Home Use
  • Toxoplasmosis and Pregnancy
  • Thermometer Project
  • Making Meat Jerky


    Links to more information
  • Pennsylvania State University food safety
  • Food and Nutrition Information Center at USDA
  • U.S. Centers for Disease Control and Prevention
  • U.S. Foodborne Illness Education Information Center
  • U.S. Government Gateway to Food Safety Information
  • Nutrition and Health Information from the US Government Websites
  • USDA Food and Nutrition Services
  • Food Safety and Inspection Service at USDA
  • WSU Cooperative Extension Bulletin Office
  • Center for Food Safety and Applied Nutrition at FDA


    WSU Bulletins
    Click here for a list of Food Safety publications you can order from WSU.

     

     
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