UNIVERSITY PARK, Pa. -- This time of year marks the migration of dining to the great outdoors -- truly summer grilling and picnicking remain a great American passion. But do it wisely, urges a food-safety expert in Penn State's College of Agricultural Sciences, and avoid common mistakes that make people sick every year. Whether you are just cooking burgers on the grill or laying out an elaborate picnic spread, preparing and eating food outdoors can present opportunities for foodborne illness to spread, said Martin Bucknavage, Penn State extension food-safety specialist.

"If you are not careful handling and preparing food outside, you can make a mistake that might result in people getting sick," he said. "Just taking a few simple precautions will insure that you, your family and guests have a great outdoor dining experience."

Bucknavage cited a few common errors people make:

--Not using a thermometer to check if foods are properly cooked. "The most reliable way to see if a hamburger or piece of chicken is cooked is to use a thermometer," he said. "Unfortunately, folks often rely on color to see if a burger is done, and this will not work.

"Each year, people get infected by E. coli or Salmonella because the food was not cooked to a temperature that kills these organisms."

First, buy a good digital thermometer. Then insert the thermometer into the thickest part of the meat to determine if it has reached the proper temperature. For hamburgers, cook to an internal temperature of at least 160 F; for chicken or other poultry, such as turkey, cook to an internal temperature of at least 165 F.

--Not keeping food cold. When you go on a picnic, be sure to keep perishable foods cold, including sandwiches, sliced tomatoes, cut lettuce and sliced melons. When it is 80 or 90 degrees outside, bacteria can grow very rapidly. Put all perishable foods in a cooler with ice packs or bags of ice.

"Staphylococcus aureus is one organism, if present, that will grow and produce a toxin causing you to become extremely ill," Bucknavage explained. "By keeping foods at a temperature below 40 F, we can minimize potential issues."

--Not keeping raw and cooked foods separate. This one is vital but is often overlooked, Bucknavage warned. When packing a cooler, it is important to keep raw foods -- especially raw meats -- in a separate cooler from ready-to-eat foods (foods that will be eaten without any further cooking).

"Too often, we try to pack everything in one cooler, and the juices from the raw meats leak onto fruits, cans of soda or buns," he said. "These raw meat juices often contain pathogenic bacteria, such as Salmonella and E. coli, and can cause infection when you consume foods or beverages that have become contaminated."

Along with this, keep utensils that have been used to handle raw meats separate from those used for ready-to-eat foods.

--Not properly washing hands. "This one sounds obvious, but you'd be amazed at how often hands are a source of contamination in outdoor food preparation -- if only because it is sometimes difficult to find a place to thoroughly wash them using soap," Bucknavage said.

If you directly handle raw meats, or if your hands touch unclean surfaces, you must wash them before touching other foods or utensils. "So, be sure to have a means for washing hands if they become soiled, especially from handling raw meats," he said. "If away from home, have a source of water available along with some soap. And don't just count on antiseptic wipes."

While wipes can help, they cannot be counted on solely to remove the material that can harbor bacteria.