Did you know? Even if you always choose nutritious ingredients, if the cooking method is improper, the nutrients can sneak away. In processing steps like washing, cutting, blanching, and stir-frying, what exactly is stealing your nutrients?
Peeling all fruits and vegetables. Many people are afraid of pesticide residues on the surface of vegetables and will usually peel them before cooking, such as eggplant skin, zucchini skin, radish skin, etc. In fact, the skins of vegetables contain a variety of nutrients such as dietary fiber, vitamins, chlorophyll, minerals, and antioxidants. Peeling them before eating actually discards many nutrients. To reduce pesticide residues, it's best to scrub fruits and vegetables vigorously under the faucet first. For firmer-skinned melons and fruits, you can also use a small brush to wash them. Once you feel they are clean, rinse them with water for 15~20 seconds before eating. Soaking in tap water can also remove some pesticide residues, but don't soak for too long; about 10 minutes is appropriate.
Cutting vegetables before washing. Many people, for convenience, cut the vegetables first and then wash them together. However, this method causes water-soluble vitamins like B vitamins and vitamin C, as well as some minerals, to dissolve into the water, resulting in loss. For example, many people soak potato shreds and eggplant shreds in water directly after cutting. Although this prevents discoloration, a large amount of nutrients is also quietly lost. Moreover, washing vegetables after cutting makes it easy for pesticide residues and soil on the surface to enter the cut surfaces. Therefore, the correct approach is to wash the vegetables thoroughly first, and try to drain the moisture before cutting. Also, when washing rice before steaming, don't rub it repeatedly, otherwise a large amount of B vitamins will also be lost.
Cutting into too small pieces. As the saying goes, "food is never too refined," but from a nutritional perspective, vegetables are not better the more finely they are cut. Because the smaller the pieces, the larger their surface area, and the greater the contact with air and the hot pan, the more severe the nutrient loss. Some nutrients will also be lost with the vegetable juice. Moreover, some people are used to pre-cutting ingredients for later use, but this can cause easily oxidized vitamins like vitamin C, vitamin E, and B vitamins to be lost. Therefore, it's best to cut and stir-fry vegetables just before cooking, and eat them right away.
Blanching vegetables for too long. Some vegetables need to be blanched in boiling water after being cut, which can remove oxalic acid and even residual pesticides, and ensure all ingredients cook evenly. However, if there is too little water in the pot or the heat is too low, the blanching time will increase, causing a significant loss of nutrients in the vegetables. The solution is to use more water when blanching, turn the heat to maximum, and shorten the blanching time. Generally, the vegetables can be removed as soon as their color changes slightly. You can also add a few drops of oil to the water to "seal" the cut surfaces of the vegetables, preventing oxidative loss.
Randomly using alkali when marinating meat. Many people like to use alkaline substances like baking soda and tenderizing powder to marinate meat to make it more tender and smooth. However, these alkaline substances can cause the protein to denature, making it difficult for the body to absorb; when fat meets alkali, a saponification reaction occurs, not only losing its nutritional value but also producing an unpleasant odor; moreover, a large amount of B vitamins in the meat will be completely lost. Normally, when marinating meat, you can mix the meat slices with salt, pepper, Shaoxing wine, egg white, and starch, then pan-fry them at an appropriate temperature. This can well preserve the nutrients and also results in a good texture.
Deep-frying ingredients first. When making dishes like Di San Xian (braised potatoes, eggplant, and green peppers) or dry-fried green beans, many people like to first deep-fry the ingredients in oil, then take them out and stir-fry them. This makes the dishes look bright and smell fragrant. However, this cooking method not only destroys the original nutrients in the dishes, but also loses the originally abundant vitamins. The meat that has been deep-fried is also not easy to digest and can lead to excessive intake of oil. Therefore, when cooking at home, it's best to skip this step and choose more cooking methods like white blanching, stir-frying, cold salads, and steaming.
Using too high oil temperature for stir-frying. Many people like to heat the oil until it smokes before adding green onions and ginger to "aromatize" the oil before stir-frying. But by then, the oil temperature is often over 200°C. Vitamin E, phospholipids, unsaturated fatty acids, etc., in the oil are easily oxidized at high temperatures, and other nutrients in the vegetables are also destroyed. In addition, when stir-frying, if the heat is too low and the cooking time is too long, a large amount of nutrients in the ingredients, such as vitamin C, anthocyanins, chlorophyll, etc., will be lost with the juice. Therefore, it is recommended to add the ingredients to the pan before the oil starts to smoke, and use high heat for quick stir-frying to shorten the heating time. Adding salt too early. Many people have the habit of adding more salt or adding it early when stir-frying. This will cause too much juice to be exuded from the vegetables, not only causing nutrient loss but also making the dish wilt and affecting the texture. If salt is added too early to meat, it will cause the protein to coagulate prematurely, which is not only difficult to digest, but also prevents the fishy smell from dissipating and the umami from the broth from infusing. It is recommended to add salt when the dish is about 70-80% cooked, or just before serving.
Adding vinegar to green leafy vegetables. Many people like to add a little vinegar to enhance the flavor when stir-frying. However, if too much vinegar is added to green vegetables, the color will turn brownish-yellow, while adding vinegar to yellow or white dishes like shredded potatoes and lotus root slices has no such effect. This is because green vegetables contain a large amount of chlorophyll and magnesium. After adding vinegar, the hydrogen in the acetic acid will immediately replace the magnesium in the chlorophyll, and this important nutrient is "stolen." Therefore, when cooking green leafy vegetables, do not add too much vinegar; it's best not to add any at all.
Pouring away all the vegetable broth. After stir-frying, many people pour away the broth in the pot. But the broth actually contains many dissolved nutrients, including hydrolyzed proteins, amino acids, various vitamins, some minerals, and antioxidants. At this point, you can thicken the broth with an appropriate amount of starch water. This not only allows these nutrients to re-adhere to the surface of the food but also forms a protective layer on the food's surface, playing a role in heat preservation and anti-oxidation.