You can't tell if a food is safely cooked by sight, smell or even taste. A food thermometer is the only way to ensure food is cooked to the proper temperature and harmful bacteria are eliminated.
A new consumer research study by the University of California – Davis suggests Americans may not always own and properly use food thermometers. According to the study, only 48 percent of participants own a food thermometer, and 69 percent of those reported that they seldom use it to check if chicken is completely cooked. Most participants determined "fully cooked" based on appearance, which is an unreliable method. Only 29 percent knew the correct USDA recommended temperature of 165°F for chicken. No participants reported calibrating their thermometers to ensure accuracy.
Contrary to popular belief, a food thermometer is not needed just for meat and poultry. A safe minimum internal temperature must be reached to avoid food poisoning in all cooked foods from egg dishes and casseroles to leftovers and microwave meals.
Always use a food thermometer and follow the appropriate steps to ensure you are doing so correctly.
Note: A food thermometer is also needed after food is cooked to ensure the temperature doesn't fall into the danger zone. The "danger zone" for perishable foods is between 40° and 140° Fahrenheit. Perishable foods are no longer safe to eat if they have been in this danger zone for more than two hours (one hour in 90° Fahrenheit or above). This is especially important for buffet and potluck-style gatherings.