Final answer:
When food drops below the safe temperature of 135°F (57°C) and stays in the 'danger zone' of 40-140 degrees F for more than two hours, it should be discarded to prevent foodborne illness. The food held at 120°F (49°C) for five hours is unsafe and should not be consumed.
Step-by-step explanation:
If a food delivery driver picks up food that has been cooked and held at a safe temperature of 135°F (57°C) but the food drops to 120°F (49°C) after a delay, the safety of the food is compromised. According to health guidelines, perishable foods should not be left at a temperature between 40 and 140 degrees F (4 to 60 degrees C) for more than two hours as this temperature range allows for the rapid multiplication of bacteria. Since the food in this scenario was held at an unsafe temperature for five hours, which is well beyond the two-hour limit, the restaurant should discard the food to prevent the risk of foodborne illness.
To prevent such occurrences, it is essential that food be kept at safe temperatures during transport. The restaurant could consider using insulated bags or containers that maintain food at proper temperatures for longer periods. Additionally, policies should be in place to ensure that the food is delivered within a safe timeframe or is otherwise deemed unsuitable for consumption.