Introduction: Many people are used to covering the wok when stir-frying, but do you know when it's best to do so?
Covering the wok while stir-frying not only prevents oil splatters but also traps heat, cooking the food faster. However, in daily life, many people don't know when to cover and when not to. Covering at the wrong time can affect the texture and significantly reduce the nutritional value. In this issue, our reporters interview several authoritative experts to teach you when to cover the wok.
Yu Renwen, a senior nutritional dietitian at the General Hospital of the Beijing Military Command, explains that covering the wok while stir-frying is essentially a "braising" method. It allows the moisture in the wok to evaporate quickly, so the high-temperature steam can cook the food in a shorter time. It also helps people reduce the amount of oil used. Whether to cover the wok during cooking depends on the specific situation.
For green leafy vegetables, stir-frying uncovered gives a crisp texture, while covering is healthier. Fan Zhihong, an associate professor at the College of Food Science and Nutritional Engineering at China Agricultural University, states that for green leafy vegetables like rape and lettuce, it's optional whether to cover. If you do cover, ensure there is a little water at the bottom of the wok before covering, and control the heat and time. Medium heat for about 20 seconds is appropriate; longer cooking can cause the vegetables to turn yellow, and overcooking will affect the texture. Chefs in restaurants generally stir-fry green leafy vegetables uncovered for a crisp and tender result. Zhu Yi, an associate professor at the same college, highly recommends the "water-stir-fry with a lid" method, which she considers the healthiest cooking method. The specific steps are: first, add a little water to the bottom of the wok; after the water boils, add the vegetables and cover immediately; once the steam rises, wait for about 20 seconds, then remove the lid, add a few drops of oil, some salt, stir a few times, and it's ready to serve.
It's best to cover the wok when cooking vegetables that are not easily cooked. Yu Renwen suggests that for vegetables with a firmer texture, such as cauliflower, potatoes, eggplants, beans, and carrots, which are not easy to cook and require repeated stirring, it's best to use the braising method. This method uses higher heat in the wok, significantly shortening the cooking time, preserving the original flavor, and retaining more nutrients. Some starchy vegetables, like potatoes and Chinese yams, are also easier to digest and absorb after being braised.
It's also a good idea to cover the wok briefly when blanching vegetables. Fan Zhihong explains that when vegetables are added to boiling water, the temperature drops. If there are many vegetables, the water may not boil again immediately. To reduce the soaking time and minimize nutrient loss, it is recommended to cover the wok to help the water come back to a boil quickly, allowing you to remove the vegetables promptly.
When stir-frying meat or eggs, do not cover the wok. When stir-frying lamb, beef, or eggs, the cooking time is short and requires constant stirring, so covering is not necessary. Covering the wok might actually affect the texture of the meat and eggs due to the excess steam.