What type of food requires refrigeration after opening to ensure safety?

Perishable foods require refrigeration after opening because they are highly susceptible to spoilage due to their moisture content and nutrient composition. These foods, which include items such as dairy products, meats, eggs, and cooked leftovers, provide an ideal environment for the growth of harmful bacteria if not stored at safe temperatures. Keeping these foods refrigerated slows down bacterial growth and helps maintain their safety and freshness for a longer period.

In contrast, canned goods are typically shelf-stable until opened, grains can be stored at room temperature, and cooking oils can also be stored in a cool, dark place without requiring refrigeration after opening. Therefore, the need for refrigeration is critical specifically for perishable foods to prevent foodborne illnesses and ensure that they remain safe for consumption.