How to Keep Food Cold at a Picnic or Barbecue

Eating outdoors is the most challenging situation because two kitchen essentials are missing: running water and a refrigerator. A table in the sun can quickly get hotter than 30°C / 85°F, making the 5–60°C / 41–140°F range where bacteria grow quickly almost the default. That is why picnic food safety is established before leaving home, not when cooking begins. What goes in the cooler, how it is packed, and how often it is opened largely determine whether the food eaten that day is safe. That is why the most important picnic preparation happens in the kitchen before you leave.

A cooler is not a refrigerator; it does not make cold, but keeps the cold it is given. So chill the cooler before leaving home and pack it with products just taken from the refrigerator. Place ice packs across the bottom and top rather than in one spot. Fill empty spaces with towels or newspaper, because air gaps speed warming. A full cooler stays cold much longer than a half-full one. Keep the cooler itself in the shade, under a cover if possible.

Arrangement is the only way to prevent cross-contamination. Put raw meat, poultry, and fish at the bottom in a leakproof, lidded container, positioned so nothing can drip onto the food below or around it. Keep ready-to-eat food, salad, cheese, and dessert on the upper layer. If possible, use two coolers: one only for raw meat and the other for drinks and ready-to-eat food. The drink cooler is opened often, so keeping it separate helps preserve the cold; some of the cool air escapes every time it is opened. When you return home, wash the container that held raw meat with hot, soapy water.

Keep things organized at the grill, too. Wash or replace the plate, container, and tongs that held raw meat before they touch cooked meat; do not use marinade as a sauce. Poultry must reach an internal temperature of 74°C / 165°F, and ground meat 71°C / 160°F. Color is even more misleading outdoors because grill smoke darkens meat early. That is why a pocket-sized thermometer belongs in the cooler. If there is no water for washing your hands, bring wet wipes and hand sanitizer. Put cooked meat on a separate plate and never return it to the place where raw meat was kept.

Time limits are stricter outdoors. Food taken out of the cooler and set on the table should not sit out for more than two hours total; if the air temperature is above 32°C / 90°F, the limit drops to one hour, which is often the relevant limit on a summer day. Take out only as much food as will be eaten; leave the rest in the cooler. Do not bring leftover ready-to-eat food home after the trip; discard it. Do not keep meat or dairy products from a cooler if the ice has melted completely and the water has become lukewarm. Leftover salads and appetizers are subject to the same limit if the trip home is long.