Putting lids on pots while cooking serves several purposes:
Heat retention: The lid helps trap heat inside the pot, creating a more controlled cooking environment. This helps to cook food faster and more evenly, as the heat is not easily lost to the surrounding air.
Faster boiling: When cooking liquids like water or broth, covering the pot with a lid helps the liquid come to a boil faster, saving time and energy.
Moisture retention: The lid helps to trap steam inside the pot, preventing the loss of moisture from the food being cooked. This is particularly useful when cooking foods that can easily dry out, such as rice or certain meats.
Even cooking: By retaining heat and moisture, the lid promotes even cooking throughout the food, reducing the risk of unevenly cooked or dried-out portions.
As for frying in pans, lids are generally not used for the following reasons:
Control of oil splatter: When frying, the high heat can cause oil to splatter. A lid would trap the moisture inside the pan and could lead to dangerous oil splatters when it escapes.
Texture and crispiness: In frying, especially when you want to achieve a crispy texture on the outside of the food (e.g., fried chicken or french fries), using a lid would trap steam and moisture, potentially making the food soggy instead of crispy.
Visual monitoring: Frying often requires visual monitoring of the food as it cooks. With a lid on the pan, it becomes challenging to see the food's progress and adjust the cooking as needed.
Instead of using a lid, techniques like flipping the food or using a splatter guard can help control the cooking process and minimize oil splatter without trapping moisture. It's important to exercise caution while frying and follow safety guidelines to prevent accidents related to hot oil.