Preparation

First and foremost keep your hands, utensils and containers clean. Prepare the food the day of the picnic unless it is to be frozen. Mayonnaise-based foods need to be kept cool. Even though mayonnaise alone is too acidic for bacteria, when it is mixed with other foods bacteria can grow if it is kept too warm. Melons are very low in acid and can therefore harbor bacteria. Be sure and keep them cool and clean.

Packing

Cold food must be kept below 40 degrees F to prevent bacterial growth. To store cold food use a heavy duty insulated cooler with plenty of ice. Plan ahead by freezing a block of ice in an empty milk carton. Keep the food dry by placing it in a zip lock bag and immersing it in the ice. When traveling, do not put the cooler in the trunk of the car. Temperatures there can reach 150 degrees F. Transport coolers in the passenger compartment of the car. At the picnic sight put the cooler in the shade and let it remain closed as much as possible to preserve the temperature. Hot foods need to be kept above 140 degrees F. Wrap them in towels and newspapers to insulate them. Food that doesn't have any special storage requirements includes peanut butter sandwiches, nuts, unpeeled fruit, unopened canned goods, cookies, cakes and crackers.

Cooking and Serving

Always wash hands and utensils before handling food. Be sure and pack extra plates and utensils because you will need to discard any material that has touched raw food. Cook food thoroughly from beginning to end at one time. Stopping midstream can provide conditions for bacterial growth. Cook poultry until the juices run clear and there is no pink at the bone. Keep cold food in the cooler until time to serve. Leftovers should be put back in the cooler immediately. Eat cooked food soon after cooking. Insects can be thwarted by covering food with a napkin or cloth. Throw away any food that has been sitting out for more than an hour. Any food left in the coler will be fine as long as ice remains. If the ice has melted get rid of the food.