Q: I appreciated your column last week on packing a safe lunch for kids. I have a college freshman who needs help on how to keep food safe, too. Any ideas?

A: Students’ schedules are extremely varied when they hit college, and they often eat whenever and wherever it is convenient. So when it comes to safely preparing meals, you’re right, many college students simply don’t know what it takes to keep food safe.

Here are some answers to several questions that I’ve received over the years about how to safely cook and prepare foods while away at school.

Q: Several slices of pizza have been left out overnight. Is the pizza still safe to eat?

A: No. Perishable food (including leftover pizza, fried chicken, Chinese food and other takeout foods) should never be away from a heat source or refrigeration more than two hours. This is true even if there are no meat products on the pizza. Foodborne bacteria that may be present on these foods grow fastest at temperatures between 40 and 140 degrees and can double in number every 20 minutes. Therefore, keep it hot (above 140 degrees) or keep it cold (below 40 degrees), and don’t let it sit out at room temperature for more than two hours (or one hour if the air temperature is 90 degrees or above).

Be sure to wrap or cover the leftover food. Cooked meat or poultry and leftover pizza is safe for three to four days, while luncheon meats, egg, tuna and macaroni salads are safe for up to three to five days. Foods stored longer may begin to spoil or become unsafe to eat. Never taste a food to determine whether it has spoiled.

Q: I will be attending a tailgate party at the stadium and grilling hamburgers. How can I be sure the burgers are fully cooked?

A: The only way to know hamburgers are safely cooked is to use a food thermometer. Do not use color as a measure of doneness. Ground beef may turn brown before it has reached a temperature at which bacteria are destroyed. A hamburger cooked to 160 degrees, measured with a food thermometer throughout the patty, is safe – regardless of color.

Also, remember that when taking raw hamburgers to the tailgate party, keep it cold to minimize bacterial growth. Use an insulated cooler with sufficient ice or ice packs to keep the food at 40 degrees or below. Pack food right from the refrigerator into the cooler immediately before leaving home. Keep the cooler in the coolest part of the car. To prevent cross-contamination, don’t put cooked or ready-to-eat food back in the cooler that contained the raw burgers.

Discard all perishable foods that have been left at outside temperatures longer than two hours.

Q: Our dorm has a kitchen with a microwave on each floor. When I microwave the food according to the package’s instructions, it’s still partly frozen. Why doesn’t it get hot enough?

A: In a large building like a dorm, electrical equipment such as computers, toaster-ovens, hair dryers and irons compete for current and reduce the electrical wattage of a microwave. A community oven that has been used just before you will cook slower than a cold oven. To compensate, set the microwave for the maximum time given in the instructions. Also, avoid using an extension cord with the microwave because power is reduced as it flows down the cord. Cover foods during cooking. Remember to stir or rearrange food and rotate the dish. Use a food thermometer to ensure the food reaches the appropriate internal temperature.

Use microwave-safe containers. Don’t microwave in margarine tubs or other plastic containers intended for cold storage. Chemicals used in such plastics could transfer into the food when heated.

Q: I frequently send “care packages” to my son at college. What other foods besides cookies, crackers and candy can I mail?

A: Shelf-stable, microwavable entrees are one option. These foods are not frozen and will stay fresh without refrigeration for about 18 months. Canned meats and shelf-stable packaged fish as well as dried meat and poultry, such as beef and turkey jerky, are safe to mail. Bacteria can’t grow in foods preserved by removing moisture.

Other convenient items that could be considered are: ready-to-eat cereal, single-serve oatmeal packets, a box of instant brown rice, dried fruits and vegetables, individually-packaged canned fruits and puddings, juice boxes, nuts and peanut butter.

Q: My daughter’s college is only a four-hour drive away, so she comes home often. How can I safely pack leftovers for her to take back to school?

A: For a four-hour drive, food must be handled properly to keep it safe from spoilage and pathogenic bacteria. Leftovers should be divided into shallow containers and cooled in the refrigerator prior to the trip. Pack the food in an insulated cooler packed with several inches of ice or frozen gel packs. The temperature inside these containers should be at or below 40 degrees. Return the food to the refrigerator as soon as possible.