All foods need to be cooked for a minimum of 15 seconds at the required temperatures and roasts need to be held at 130 degrees F for 112 minutes before serving. The metal stem thermometer measures the inside, or internal, temperature of the food.ll foods need to be cooked for a minimum of 15 seconds at the required temperatures and roasts need to be held at 130 degrees F for 112 minutes before serving. The metal stem thermometer measures the inside, or internal, temperature of the food.