Final answer:
The tuna salad held at 71°F for four hours exceeds the safe temperature threshold and should be thrown out to prevent the risk of foodborne illness.
Step-by-step explanation:
The cold tuna salad at 71°F should be discarded immediately. Per food safety guidelines, perishable foods that remain above 40°F (4°C) for more than two hours can rapidly grow bacteria and become unsafe to eat. In this case, since the tuna salad has been held at an unsafe temperature for four hours, it is far beyond this two-hour threshold and poses a risk of foodborne illness.
It is imperative to maintain proper temperature control to inhibit bacterial growth. Cold foods must be kept at or below 40°F, and any deviation above this temperature for a prolonged period increases the potential for harmful bacteria to multiply to dangerous levels. Using a thermometer to regularly check food temperatures in a buffet or any situation where food is held for service is a best practice for food safety. To be clear, reheating the tuna salad will not make it safe because some bacteria produce toxins that are not destroyed by heat. Therefore, reheating would not be sufficient to prevent foodborne illness.