Diane laughs as she recalls carrying a peanut butter and jelly sandwich to school every day for some eight years:  “It was the only meal my mother considered safe to consume after being unrefrigerated all morning.” Today, we know that safety doesn’t require such monotony.  However, the challenge remains—how to pack nutritious, delicious meals that will remain uncontaminated even if they spend all morning on a coatroom floor.

Perishable foods (those that need to be kept hot or cold) must not be left in what food scientists call the “danger zone” (40°-140°F; 4°-60°C)  for more than two hours. Bacteria and other pathogens that can contaminate foods and cause illness grow rapidly in that temperature range.  Children’s lunches, if left unrefrigerated for about four hours, must contain only shelf-stable items, or parents must learn a few techniques for keeping hot food hot and cold food cold. (These tips will also come in handy when adults prepare their own portable lunches.)