Final answer:
Pizza left out at room temperature for more than 4-5 hours must be thrown away to prevent foodborne illness, as reheating it does not make it safe for consumption.
Step-by-step explanation:
Pizza that has been held for more than 4-5 hours at room temperature must be thrown away. This is a food safety guideline to prevent foodborne illness. Foods meant to be eaten hot should be kept hot until served, and similarly, foods meant to be eaten cold should be refrigerated until served. If perishable food items, such as pizza, are left at a temperature between 40 and 140 degrees Fahrenheit for more than two hours, they should be discarded because of the risk of bacterial growth.
Keeping the temperature in the refrigerator at or below 40 degrees Fahrenheit (4 degrees Celsius) is crucial for inhibiting bacterial growth in refrigerated foods. Should the temperature rise above this threshold for two hours or more, the food may no longer be safe to eat. Therefore, pizza left at room temperature for an extended period cannot be made safe by simply reheating and must be thrown out to avoid the risk of foodborne diseases.