When stewing soup in casserole, heating for too long will lead to the degradation of protein in meat ingredients, and a large number of gel components will seep out, which will increase the toughness of meat, resulting in poor taste of meat food in use, which is not conducive to human digestion and absorption.

Casserole is a cooking tool with good sealing effect. When cooking mutton, ribs and other foods with strong flavor, it will make the smell difficult to dissipate, thus affecting the flavor of the food. Moreover, some harmful substances, such as fatty acids, can not be completely volatilized, stay in food and soup, and generate harmful substances through long-term thermal reaction.

In the process of making casserole, minerals such as timely and feldspar will be used. Some casseroles are also glazed, so there are some harmful substances in the glaze. These substances will penetrate into food in the process of casserole cooking and stewing, which will affect human health and even cause chronic poisoning.

Moreover, if the casserole is stewed for a long time, the average loss rate of nutrients will increase, especially for some vegetables containing a lot of inorganic salts such as calcium, phosphorus, iron, zinc, iodine and vitamin C, all nutrients will be lost. Therefore, it is suggested that raw vegetables and coarse grains should be added when eating casserole to make up for the loss and deficiency of nutrition.