Whether it's off to school or work or an out of town sports event, many of us pack and carry "bag" lunches. Food brought from home can be kept safely until mealtime if these guidelines from the United States Department of Agriculture's Food Safety and Inspection Service are followed.

Perishable food, such as raw or cooked meat and poultry and deli meat, must be kept cold or frozen at the store and at home. In between, transport perishable food as fast as possible when no ice source is available. At the destination, it must be kept cold. Food should not be left out at room temperature more than 2 hours (1 hour if the temperature is above 90°F).

Prepackaged combos that contain luncheon meats along with crackers, cheese, and condiments must also be kept refrigerated. This includes luncheon meats and smoked ham which are cured or contain preservatives.

Why keep food cold? Harmful bacteria multiply rapidly in the "Danger Zone" -- the temperatures between 40 and 140°F. So, perishable food transported without an ice source won't stay safe long.

Wash your hands before you prepare or eat food. Wash cutting boards, dishes, utensils, and countertops with hot, soapy water after preparing each food item and before you go on to the next item. A solution of 1 tablespoon of unscented, liquid chlorine bleach in 1 gallon of water may be used to sanitize surfaces and utensils. Keep family pets away from kitchen counters.

Harmful bacteria can spread throughout the kitchen and get onto cutting boards, utensils, and countertops. Always use a clean cutting board. If a cutting board has been used to cut raw meat and poultry, be sure to wash it before cutting food that will not be cooked, such as bread, lettuce, and tomatoes. It's best to use one cutting board for fresh produce and a separate one for meat and poultry.

At mealtime, discard all used food packaging and paper bags. Do not reuse packaging because it could contaminate other food and cause foodborne illness.

Pack just the amount of perishable food that can be eaten at a meal. That way, there won't be a problem about the storage or safety of leftovers.

It's fine to prepare the food the night before and store the packed lunch in the refrigerator. Freezing sandwiches helps them stay cold. However, for best quality, don't freeze sandwiches containing mayonnaise, lettuce, or tomatoes. Add these later.

Insulated, soft-sided lunch boxes or bags are best for keeping food cold, but metal or plastic lunch boxes and paper bags can also be used. If using paper lunch bags, create layers by double bagging to help insulate the food. An ice source should be packed with perishable food in any type of lunch bag or box. A small frozen gel pack or frozen juice box works well. Of course, if there's a refrigerator available, store perishable items there upon arrival.

Prepare cooked food, such as turkey, ham, chicken, and vegetable or pasta salads, ahead of time to allow for thorough chilling in the refrigerator. Divide large amounts of food into shallow containers for fast chilling and easier use. Keep cooked food refrigerated until time to leave home.

Some food is safe without a cold source. Items that don't require refrigeration include fruits, vegetables, hard cheese, canned meat and fish, chips, breads, crackers, peanut butter, jelly, mustard, and pickles.

Use an insulated container to keep food like soup, chili, and stew hot. Fill the container with boiling water, let stand for a few minutes, empty, and then put in the piping hot food. Keep the insulated container closed until lunchtime to keep the food hot -- 140°F or above.

When using the microwave oven to reheat lunches, cover food to hold in moisture and promote safe, even heating. Reheat leftovers to at least 165°F. Food should be steaming hot. Cook frozen convenience meals according to package instructions.