The brown bags that carried your childhood lunches were perfect for turning into cafeteria hand puppets, but they couldn't keep food cold. Perishable foods become unsafe to eat after just two hours at room temperature. For the lunch you pack at 7 a.m. to be safe to eat at noon, use advance planning and a few exterior cooling devices.
An insulated, soft-sided bag is the best lunchbox choice, according to the U.S. Department of Agriculture, which also recommends including at least two cooling sources with a packed lunch. If your only option is a hard lunchbox, choose one with a central compartment. Small divided compartments are too small to accommodate ice packs. Keep a stash of gel ice packs, no smaller than 5 by 3 inches, in the freezer. Wash the lunch bag or box and packs after every use in hot soapy water.
Before washing your lunch bag and returning ice packs to the freezer, toss any leftover food from that day's lunch. Prepare and package any perishable foods, like a turkey sandwich, that you’ll put into the next day’s lunch. Additionally, any peeled or cut fruits or vegetables should be prepared at night and refrigerated. Freeze a bottle of water or juice to keep the lunch extra cold; it will thaw by midday. You may also freeze a sandwich, though the USDA warns against freezing a sandwich containing mayonnaise, lettuce or tomato.
You may wait until morning to prepare foods that can be stored at room temperature. When packing the lunchbox, first arrange the perishable items so that each one has contact with at least one ice pack; then add the nonperishable items. A large lunch may require more than two cold sources to be properly chilled, and you may count a frozen sandwich or drink bottle as a cold source. Keep the lunchbox in the refrigerator until leaving home.
Even if the lunch has been chilled with several cold packs, it’s most safely stored in a refrigerator until lunch. Most schools don’t have the space to refrigerate a child’s lunchbox, but a smaller preschool or your office may. Open the lid to let the refrigerator’s cold air reach the food inside. If you find yourself without chilled ice packs, fill the lunchbox with items that don’t need to be kept cold. Peanut butter, hard cheese, whole and uncut vegetables or fruit, pickles and unopened cans of fruit, meat, fish and poultry are safe at room temperature.