Final answer:
Cold salad bars are chilled to below 4°C primarily to prevent pathogens from multiplying in the food, reducing the risk of foodborne illnesses.
Step-by-step explanation:
The reason cold salad bars must be chilled to hold food at or below 4°C is to prevent pathogens from multiplying in the food. This temperature level inhibits the metabolism and growth of microorganisms, thereby helping to preserve the safety and quality of the food. While refrigeration does not kill pathogens, it significantly slows their growth, thus decreasing the risk of foodborne illnesses. Foods left at a temperature range between 4°C and 60°C for more than two hours can become unsafe to eat due to the rapid growth of bacteria.