Ahead of the Fourth of July holiday, we talked to Dr. Qinchun Rao, Betty M. Watts Endowed Professor in the Nutrition and Food Science program. He spoke about what everyone can do to make sure they keep their food safe while enjoying outdoor picnics and get-togethers
Ahead of the Fourth of July holiday, we talked to Dr. Qinchun Rao, Betty M. Watts Endowed Professor in the Nutrition and Food Science program. He spoke about what everyone can do to make sure they keep their food safe while enjoying outdoor picnics and get-togethers, when the hot weather can turn a perfectly good event into a gastronomic nightmare — or worse!
How long is it safe to leave cooked meats like pork ribs, hamburgers, or grilled chicken out at room temperature? Similarly, how safe is it for those foods to be left outside on serving trays during a summer cookout?
Qinchun Rao: Cooked meats should not be left out at room temperature for more than 2 hours. However, if the ambient temperature is above 90°F, as is common during summer cookouts, the safe window shortens to 1 hour. This applies whether the food is indoors or outdoors. After this time, bacteria can multiply rapidly in the “danger zone” between 40°F and 140°F, increasing the risk of foodborne illness.
What about cold dishes or mayonnaise-based dishes like potato salad, pasta salad, or deviled eggs? Is there a time limit before they should be refrigerated or discarded?
QR: Cold or mayonnaise-based dishes are particularly susceptible to bacterial growth. These should also be kept out for no more than 2 hours, or 1 hour if the temperature exceeds 90°F. To keep them safe, they should be stored at or below 40°F, ideally in a cooler with ice or on a bed of ice while being served.
Are there any foods that are especially risky to serve outdoors in the heat without proper cooling?
QR: Yes, foods that are high in protein and moisture, such as dairy products, eggs, seafood, cooked meats, and mayonnaise-based salads, are especially risky. These items provide an ideal environment for bacteria like Salmonella and Listeria to thrive if not kept at safe temperatures.
Is there a general outdoor temperature—or temperature range—that puts food at greater risk for spoilage or foodborne illness?
QR: The USDA defines the “danger zone” as the temperature range between 40°F and 140°F. Within this range, bacteria can double in number in as little as 20 minutes. Outdoor temperatures above 90°F are particularly hazardous, as they accelerate spoilage and reduce the safe exposure time to just 1 hour.
What are some simple ways people can keep food safe at an outdoor event—like using foil to cover food, coolers, ice packs, or food thermometers?
QR: To keep food safe outdoors, use insulated coolers with ice packs for cold items and chafing dishes or insulated containers for hot foods. Always use a food thermometer to ensure meats reach safe internal temperatures (e.g., 165°F for poultry, 160°F for ground meats). Cover food with foil or lids to protect from insects and sun, and serve in small batches, replenishing from coolers as needed.
Are there any common food safety myths you often hear around summer barbecues or potlucks?
QR: A common myth is that “if food smells and looks fine, it’s safe to eat.” In reality, many harmful bacteria do not alter the taste, smell, or appearance of food. Another myth is that “reheating food will kill all bacteria.” While reheating can kill some bacteria, it may not destroy toxins already produced by bacteria like Staphylococcus aureus.
If food has been sitting out for a few hours on a kitchen counter (indoors) is it still safe to take leftovers home, refrigerate, and eat later? Or is it better to throw it out?
QR: If perishable food has been left out for more than 2 hours (or 1 hour in hot conditions), it should be discarded. Refrigerating it after this period does not make it safe, as bacteria may have already multiplied to dangerous levels. It’s safer to throw it out than risk foodborne illness.
What are some risks associated with eating food that has been sitting out too long? Which types of foods pose the greatest health risk in terms of spoilage and foodborne illness?
QR: Eating food that has been left out too long can lead to foodborne illnesses caused by bacteria such as Salmonella, E. coli, and Listeria. Symptoms may include nausea, vomiting, diarrhea, and fever. The most hazardous foods include meats, poultry, seafood, dairy products, eggs, and moist cooked grains or vegetables, especially when not kept at safe temperatures.
