Eating outside is one of the joys of summer. Picnics, barbeques, and camping are all opportunities to dine al fresco. But when packing food, you don’t want to bring along any uninvited guests who might spoil both the fare and the fun. Pathogenic (disease-causing) bacteria can grow very fast in some foods when left at warm temperatures. Set your mind at ease with these simple precautions from Ken Noll, professor of molecular and cell biology at the University of Connecticut.
Q. I’ve heard that foods with mayonnaise can cause food poisoning. Is this true and, if so, what can I do about it?
Yes, this is true, but the mayonnaise is not the problem. Commercially prepared mayonnaise is safe because it is made from pasteurized ingredients and contains salt and vinegar that inhibit the growth of bacteria. The problem lies with the foods that mayonnaise is commonly mixed with to make salads such as pasta, potatoes, eggs, chicken, or tuna. These foods add proteins for pathogens to grow on. Such salads should be kept below 40°F (refrigerator temperature) until just before eating. They should not be left out after serving. All picnic foods should be returned to coolers after an hour if it is above 90°F or two hours if below 90°F to prevent spoilage. If food sits out longer, throw it away.
Q. How do I keep food in the car before we eat at our picnic?
However you park your car and wherever you store unprotected food in the car, the food will be at temperatures that are perfect for pathogenic bacteria. All picnic food should be kept in a cooler packed with ice. Large blocks of ice work better than cubes. You can freeze water in cleaned milk cartons or plastic jugs. Pack the food directly from the refrigerator immediately before leaving home. Place meats at the bottom to prevent them from dripping on other foods. Pack drinks in a separate cooler from the food so you don’t have to open the food cooler as much.
Q. How do I know when barbequed chicken and hamburgers are done? If they are pink inside, are they safe to eat?
You cannot use the color of the meat or its juices to judge if it has been cooked thoroughly. Even after all the pink is gone, contaminating bacteria can remain. The only way to know that meat is properly cooked is to measure the inside temperature with a thermometer. Digital thermometers measure temperatures at their tips so it’s easier to use these with hamburgers and small pieces of chicken. A dial thermometer measures temperature as an average over the length of its metal stem. Both kinds of thermometers must be inserted deep into the meat to make sure the inside has been heated to the proper temperature.
Minimum cooking temperatures for meats
whole poultry 165°F
poultry breasts 165°F
ground poultry 165°F
ground meats 160°F
beef pork, lamb and veal (steaks, roasts and chops) 145°F (allow to rest at least 3 minutes)
Precooked hot dogs 165°F (steaming)
Q. I read about food poisoning from melons and vegetables. Do I have to keep them cold, too?
Yes, fruits and vegetables should be kept in coolers. Place them above meats to prevent any meat juices from dripping on them. Before you leave home, wash all fruits and vegetables with cool tap water. Wash produce before you peel it. Bacteria on the peel can be transferred into the fruit or vegetable with the knife. For firm produce such as melons or cucumbers, scrub them with a clean produce brush. Remove outer leaves of lettuce or any leaves that are wilted or discolored. If you chop your vegetables, use a different cutting board than that used with meat.
Q. I wipe my kitchen counters and cutting boards while I’m preparing food to eat outside. Does that make it safer to eat?
Wiping your food preparation surfaces is a smart idea, but make sure your sponge or dishcloth is clean or you will simply spread potentially harmful microbes around your kitchen. You should disinfect your sponge or cloth daily, especially in warm summer weather when pathogens grow faster. You can wash it with your dishes in the dishwasher or moisten it and heat it in your microwave for one minute at full power. Be careful when you take it out as it will be boiling hot. Replace your sponge or cloth frequently even if you disinfect it regularly. Wipe up meat juices with a disposable paper towel and then clean the surface with soap and water or a disinfectant like lemon oil or dilute bleach. Most importantly, wash your hands when you handle food, especially after touching raw meat.
Additional food safety tips and resources are available on the US Department of Agriculture’s website.
For another view of microbes, see ‘Magnificant Microbes’ Offers Kids New View of the World