Final answer:
Foods must be cooled from 20 to 4 degrees Celsius within 4 hours to prevent the growth of bacteria and ensure food safety. It is critical to follow these timeframes and keep refrigerators below 4 degrees Celsius to maintain food safety.
Step-by-step explanation:
Foods must be cooled from 20 to 4 degrees Celsius within a specific timeframe to prevent the growth of bacteria and ensure food safety. According to food safety guidelines, perishable foods should not be left at temperatures between 4 and 60 degrees Celsius (40 and 140 degrees Fahrenheit) for more than two hours, as this can lead to rapid bacterial growth, making the food unsafe to consume.
Therefore, the correct answer to the question of how quickly foods must be cooled from 20 to 4 degrees Celsius is: (b) 4 hours.
It is important to adhere to these guidelines to maintain food safety and reduce the risk of foodborne illness. Additionally, maintaining the refrigerator temperature at or below 4 degrees Celsius (40 degrees Fahrenheit) is crucial for inhibiting bacterial growth in refrigerated foods.