Which of the following practices is essential in food safety regarding temperature control?

Properly reheating leftovers is crucial in food safety because it ensures that any harmful bacteria that may have developed while the food was stored are effectively eliminated. When food is reheated to the appropriate temperature, it not only becomes safe to consume but also retains its quality. The recommended temperature for reheating leftovers is at least 165°F (74°C), which is high enough to eradicate most pathogens.

Maintaining proper temperature control is essential in preventing foodborne illnesses, as harmful bacteria thrive between 40°F and 140°F (the "danger zone"). While refrigerating food to keep it cool is also an important practice, the question specifically relates to the action of reheating leftovers. Keeping food at room temperature or using metal containers for cooling, while they may have roles in food temperature management, do not specifically address the need to kill bacteria present in reheated food. Thus, the importance of reheating leftovers to a safe temperature is what makes this practice essential in food safety.