* All types of insulated containers should be cleaned thoroughly after each use.
* Pack the food cold or even freeze parts of it. Sandwiches can be frozen, especially coarser breads. Although its consistency will change somewhat, yogurt can also be frozen.
* Discard any leftover lunches.
* Be sure to use clean knives and cutting boards when preparing lunch the night before. Make sure the lunch is refrigerated overnight.
* Include fresh fruits, vegetables, cheeses and raisins in the lunch box. They keep well.