MISSISSIPPI STATE -- Handling food safely is a science, and those preparing food should make sure they have the tools needed to do it right.

Melissa Mixon, human nutrition specialist with Mississippi State University's Extension Service, said bacteria can grow rapidly when food is between 40 and 140 degrees. Perishable foods in this temperature zone have a two-hour window in which they are safe.

"The rule of thumb is that anytime a food has been in that temperature zone for two hours or more, don't eat it," Mixon said.

Accurate thermometers are the only way to ensure food reaches the correct degree of doneness, then is stored at the correct, safe temperature. Mixon urged cooks to get quality thermometers for the refrigerator, freezer and cooking applications.

"Using thermometers in food preparation is the only reliable way to ensure that the product has reached the appropriate temperature," Mixon said. "Foods have to be cooked to a certain internal temperature to kill any organisms in the food. Using the food's visual appearance is not a viable way of determining doneness."

Several thermometers allow consumers to determine the internal temperature of food. Digital varieties typically give faster readings and are more expensive, while the more traditional dial thermometers can be just as accurate. Purchase one that can be calibrated for accuracy.

Digital thermocouple thermometers give a reading in two to five seconds and are the most expensive type available. They can be used on all foods and are effective on thin products such as hamburgers since the sensing area is on the tip of a slender probe.

The digital thermistor has a 1/8 inch-thick probe and gives a reading in 10 seconds. Do not leave either the thermistor or thermocouple thermometers in food while it cooks.

An oven cord thermometer allows a reading to be made without opening the oven. The thermometer is inserted into the food prior to cooking, and a cord connects to an external base which displays the temperature. For the grill, thermometer-fork combinations make checking the doneness of a product easy.

"Most of these have a digital display or a light that indicates in two to 10 seconds if the product has reached medium-well or well done," Mixon said. "These can be set for the type of meat being cooked, but generally cannot be calibrated. When using a fork thermometer, be sure to stick it in the thickest part of the meat."

Many people are familiar with dial food thermometers, bimetallic thermometers with a sensing tip about 2 inches from the bottom of the probe. These are inserted into food and a temperature reading is taken in 15 to 20 seconds. They usually can be calibrated.

An oven-safe variety of the bimetallic thermometer is available. To prevent the possibility of the metal probe heating the food around the probe hotter than the rest of the dish, insert the thermometer into a new spot and read after one minute.

Pop-up thermometers are still used, and often come pre-inserted into large meats such as turkeys. One-time use, instant-read thermometers are available. These can be bought to display temperature ranges for specific foods. Once used, it changes color and can't be used again.

After food has been safely cooked, it must be chilled and stored correctly. Mixon said all refrigerators and freezers should have an accurate thermometer placed where it can be read as soon as the door is opened.

"The refrigerator temperature should not be higher than 40 degrees, and frozen foods hold longer if they're kept at 0 degrees or below," Mixon said. "Bacteria can grow in the refrigerator even at 44 to 45 degrees."

Mixon said most microorganisms that make people sick are destroyed when food is cooked to 140 to 160 degrees. After cooking, new bacteria can grow if it is not stored safely. When eating leftovers, reheat to 165 to destroy anything that may have grown in the food since it was last cooked.

Mixon said key to preparing and eating safe foods is to prevent it from staying in the temperature danger zone for more than two hours.

"The clock starts ticking once you take the food at the grocery story out of the freezer or the refrigerator," Mixon said. "It ticks while the food is being carried home and sets on the counter as it is prepared. The clock doesn't restart after cooking, so be sure to chill any leftovers quickly and reheat it thoroughly before eating."