Yes, it is normal for certain foods to turn slightly black or develop dark spots when cooked in an iron kadhai (also known as a karahi or wok). This is a common occurrence and not a cause for concern. The discoloration is primarily due to the natural reaction between the iron and certain acidic or moisture-rich ingredients present in the food.
Here's why it happens:
Iron Reactivity: Iron cookware, including kadhai, can react with certain foods, particularly those that are acidic or contain moisture. The iron from the kadhai can react with compounds in the food, leading to slight darkening or blackening of the surface of the cookware and, in some cases, the food.
Caramelization: When you cook certain ingredients like onions or sugars in an iron kadhai, they may caramelize and turn brown or black. This is a normal process that adds flavor and richness to the dish.
Seasoning: Over time, as you use your iron kadhai more frequently, it develops a natural non-stick coating called seasoning. This seasoning process can also contribute to a darker appearance of the kadhai and may impart color to the food being cooked in it.
While the blackening or darkening of the kadhai and the food might look unusual to those who are not familiar with iron cookware, it is perfectly normal and safe. In fact, many people value iron kadhai for their ability to enhance the flavor of certain dishes and provide even heat distribution.
To minimize excessive blackening and to maintain the kadhai properly:
Season the Kadhai: Before using a new iron kadhai or if the seasoning has worn off, season it properly. This helps create a natural non-stick surface and reduces the reactivity between iron and food.
Avoid Acidic Foods: Limit the use of highly acidic foods like tomatoes and tamarind in an iron kadhai, as they may cause more discoloration.
Dry the Kadhai Properly: After washing the kadhai, make sure to dry it completely to prevent rusting. A well-seasoned and dry kadhai is less likely to react with food.
Remember that a well-maintained and seasoned iron kadhai can last a long time and can be a valuable addition to your kitchen for a variety of cooking needs.