Final answer:
Food must be heated to at least 74 deg C before being placed in a hot-holding unit to prevent bacterial growth and ensure food safety.
Step-by-step explanation:
Before putting food into a hot-holding unit, the food must be heated to at least 74 deg C to ensure that any bacteria present are killed and to prevent the multiplication of microorganisms. This is essential for food safety, as bacteria generally multiply most rapidly at temperatures between about 4- and 60-degrees C. By heating the food to 74 deg C or higher, it is brought beyond the danger zone for bacterial growth, thus reducing the risk of foodborne illnesses.