Why is special attention paid to the cooking methods of vegetables?
The purpose of giving children vegetables is to obtain vitamins, minerals, and other nutrients. Therefore, a very important point is how to get these nutrients into the body completely. This requires attention to proper cooking methods. Unreasonable cooking methods can lead to the loss of all vitamins and minerals. Although you eat the vegetables, you don't get the nutrients and may still suffer from nutritional deficiency diseases. Therefore, to preserve the vitamins and minerals in vegetables, it is necessary to pay attention to reasonable cooking methods.
The effect of different cooking methods on vitamin C in vegetables
1. Stewing: The loss rate of vitamin C is 8.1~33.5%, with an average of 23.6%. However, the loss varies with the stewing time. After 10 minutes, the loss rate is 0.4~45.2%, and after 30 minutes, it increases significantly to 11.4~66.9%.
2. Boiling: The loss rate of vitamin C is 15.3~19%. About 50% of the vitamin C remaining after boiling is in the cooking water. If you only eat the vegetables and not the soup, the loss rate exceeds 60%. Squeezing the juice from the vegetables after boiling results in the greatest loss of vitamin C, up to 83.3%.
3. Stir-frying: When green vegetables are cut into sections and stir-fried with oil for 5~10 minutes, the vitamin C loss rate is 36%. For bok choy stir-fried with oil for 11~13 minutes, the loss rate is 31%. For spinach cut into sections and stir-fried with oil for 9~10 minutes, the loss rate is 16%. For tomatoes peeled and cut into cubes, stir-fried with oil for 3~4 minutes, the loss rate is only 6%. For chili peppers cut into shreds, stir-fried with oil for 1.5 minutes, the loss rate is 22%. For cabbage cut into shreds, stir-fried with oil for 11~14 minutes, the loss rate is 32%. The above shows that the longer the stir-frying time, the more vitamin C is lost, with the exception of tomatoes. Tomatoes are acidic foods and contain less ascorbic acid oxidase, which makes vitamin C more stable and less easily destroyed. Generally, by stir-frying quickly over high heat, the vitamin C loss rate can be controlled between 10~30%.
4. Storing cooked vegetables: Sometimes, if cooked vegetables are not eaten promptly and are stored for 20 minutes to 1 hour, the vitamin C loss rate can be 73~75% compared to before cooking.
5. Reheating frozen cooked vegetables: If cooked vegetables are not eaten in time and are refrigerated to prevent spoilage, then reheated before eating, vitamin C is also lost, with a loss rate of 14~17% of the cooked vegetables.
Does adding starch when cooking vegetables have a protective effect on vitamin C?
When making stewed dishes or soups, adding starch to thicken them has two advantages: one is to make the dish or soup thicker, and the other is that starch contains glutathione. The sulfhydryl group (-SH) in the structure of glutathione is reducing. During the cooking process, the sulfhydryl group is quickly oxidized, which prevents or reduces the oxidation of vitamin C, thereby protecting it. Meat also contains sulfhydryl groups, which, when cooked together with vegetables, also has a protective effect on the vitamins in the vegetables.