First, store
Office workers are busy at work, and many people are used to making big purchases once a week, and storing the purchased vegetables at home and eating them slowly. But it is unhealthy to store vegetables for a long time before eating. Do you know that vegetables lose a lot of nutrients every day if they are kept for a long time? For example, under normal circumstances (20), the loss of vitamin C is as high as 84% per day. Therefore, the first thing to prevent the loss of nutrients in vegetables is to buy fresh vegetables. For some seasonal vegetables, it is best to buy a small amount often, instead of buying a lot at a time and throwing it in the refrigerator every three to five days. Compared with ordinary vegetables, some vegetables (such as tomatoes and green peppers) lose less nutrients and can be preserved for a little longer.
Studies have shown that low temperature can reduce the loss of vitamins. The vitamin C content of fresh Chinese cabbage will not decrease if it is kept in the refrigerator for a week. Without a refrigerator, storing vegetarian dishes in a dark, ventilated and dry place can also reduce the loss of vitamins.
Low temperature can delay the deterioration of vegetables, but the lower the temperature, the better. The suitable storage temperature of most vegetables is 3-10. But cucumber is an exception, and its storage temperature should not be lower than 10. If it is stored in the refrigerator at about 4℃, the color of cucumber will become darker, the body of cucumber will become soft, transparent colloidal liquid can be seen after cutting, and the fragrance of cucumber will be lost.
It should be noted that the method of directly stuffing vegetables into the refrigerator without treatment after purchase is not scientific, and it is very particular to store vegetables in the refrigerator.
If it is a leafy vegetable, before putting it in the refrigerator, you should first remove the dirt, residual branches and broken leaves attached to it, and there is no need to clean it. If it must be cleaned, it must be cleaned and drained. Then wrap the stems down with a perforated plastic bag (easy for air circulation) or clean paper and put them in the lowest drawer of the freezer.
Root vegetables or flowers and fruits, such as radish, eggplant, sweet pepper lettuce, asparagus, etc. Wipe it clean with cloth or paper towel before putting it in the refrigerator, then put it in a plastic bag to fasten the mouth of the bag, or wrap it tightly with plastic wrap, or wrap it in two layers of paper, and then put it in the lowest layer of the refrigerator for preservation.
No matter which storage method, it is better to eat it as soon as possible when it is fresh.
Second, processing
Vegetables should be cleaned and processed after they are bought, and these processes are also the main ways of nutrient loss. If we don't pay attention, vegetables can provide us with a lot of vitamins, and there is not much left before cooking.
1, reasonable cleaning, locking nutrition.
Some people like to soak in water for a long time to reduce pesticide residues. In fact, there are many mysteries about vegetable cleaning. Generally speaking, the more times vegetables are washed, the longer they are soaked and the more nutrients are lost. In particular, some water-soluble vitamins contained in fruits and vegetables are lost faster after soaking in water.
The method of soaking to remove pesticides is not effective for all vegetables. Some scientists have done experiments, soaking beans with more than 90% pesticide residues in water for one hour, 1.5 hours, two hours. Then the pesticide residues were detected, and the results showed that there was little difference among them. Because many pesticides are ester-soluble and insoluble in water.
In order to prevent nutrient loss, it is best to wash vegetables with running water, without soaking or washing too often.
2. Losing leaves means losing nutrition.
People's accustomed vegetable processing method is also a factor of nutrient loss. Like throwing away celery leaves. In fact, the carotene content in celery leaves is much higher than that in celery stems. For example, in the outer layer of Chinese cabbage, the content of carotene in green leaves is 2 1 times that of white leaves in the inner layer, iron is 3 times, and vitamins are 1.5 times. The contents of calcium, iron and vitamin A in the green leaves outside lettuce are higher than those in the stems of lettuce.
In addition, some people pinch off both ends of bean sprouts, throw away the white sponge part of green pepper seeds and throw away the white core of wax gourd. In fact, these treatment methods are all wrong. The most nutritious part of bean sprouts is not white stalks, but pale yellow watercress, which has 2-3 times more vitamin C than the bud: the white core of green pepper and wax gourd are places with particularly high vitamin C content, so it is a pity to throw them away.
Almost every part of vegetables has nutritional value. Green leaves are the "factory" for plants to synthesize nutrients and the essence of nutrition. Throwing away green leaves will greatly reduce the nutritional value of vegetables. Try to eat completely natural food. Don't pursue a "realm" that is particularly crisp, white and sweet. If you think they are harmful in color or taste, you can adjust the cooking method or make another dish separately. For example, "fried eggplant skin" and "mixed radish skin" in old Beijing are a combination of characteristics, nutrition and food.
3. Processing sequence: wash first and then cut.
The method and sequence of changing kitchen knives are also closely related to nutrient loss. Vegetables should be washed first and then cut to avoid the loss of vitamins with water. For example, chopped Chinese cabbage can lose 30% vitamin C after washing. If cut vegetables are not fried for a long time, exposure to the air will also destroy some vitamins. For example, the preservation rate of vitamin C is 67% one hour after slicing cucumber and 50% three hours later. When radish was twisted into filaments and left at 10 for 24 hours, vitamin B 1 lost 27%. The loss of vitamin B 1 in sweet potato shreds is 2 1%. After the tomatoes were pulped and put on the next day (24 hours), only 60% of vitamin C was retained.
Never think that cutting before washing is cleaner. In fact, cutting before washing not only makes it easier for water-soluble vitamins to escape into water, but also destroys the structure of plant tissues and cells, so that nutrients are lost due to long-term exposure to air. So don't store the vegetables for too long after cutting, and cook them as soon as possible.
In addition, when making the stuffing of wonton and steamed stuffed bun, you should cut the vegetables very finely, which will cause a lot of juice to flow out. Some people squeeze out the juice for the convenience of molding or stuffing, so that 70% of the vitamins and minerals in the dish are discarded. The correct way is to chop vegetables, dried mushrooms and meat together and stir them so that the juice of vegetables can penetrate into other fillings.
Third, cooking.
1, the loss of quick frying is the smallest.
Vitamin c and B 1 afraid of heat and cooking. According to the measurement, the loss of vitamin C in hastily fried vegetables is only 1.70%, and the loss of vitamin C in vegetables is 59% if they are braised after frying. Therefore, stir-fry should use urgent fire, so that the fried dishes are not only delicious in color, but also less in nutritional loss. Vitamin c in vegetables is easily oxidized and decomposed when heated, and the loss is less when fried quickly or covered for a short time. According to research, if you burn 10 minutes, vitamin C will be reduced by 60% or even more.
There are only four words for cooking, "stir-fry", because the longer you cook, the more vitamins C and B 1 in vegetables will be lost. Even if you want to make vegetable soup, you should wait until the water boils before putting the vegetables in the pot, so as to minimize the cooking time of the vegetables in the water.
2. Eat soup while it is hot.
In order to save time, some people like to cook the dishes in advance and then wait for everyone to eat together in the pot or eat them while they are hot next time. In fact, vitamins in vegetables can lose 25% in the process of heating up after burning. If the cooked Chinese cabbage is heated for 15 minutes, it will lose about 20% of vitamin C, 30 minutes later it will lose 10%, and 20% after one hour. If vitamin C in vegetables loses 20% during cooking, 25% when dissolved in vegetable soup, and 20% when heated on fire for 15 minutes, that is, 65%. Then we don't get much vitamin C from vegetables. Many people like to eat green vegetables but don't like vegetable soup. When cooking, most vitamins are dissolved in vegetable soup. Take vitamin c as an example. After the Chinese cabbage is fried, 70% of vitamin C is dissolved in vegetable soup, fresh peas are boiled in water for 3 minutes, and 50% of vitamin C is dissolved in the soup.
3. Take certain protective measures.
The loss of food during cooking can't be completely avoided, but if some protective measures are taken, more nutrients can be preserved in vegetables.
(1) put vinegar. Because vitamins are afraid of alkali and acid, try to put vinegar in vegetables. Even when cooking animal raw materials, vinegar can dissolve more calcium in raw materials, thus promoting the absorption of calcium.
(2) thicken. Thickening can make the soup mix into a whole, so that some extracted ingredients can be taken together with vegetables.
(3) Pay attention to cover the pot to prevent water-soluble vitamins from losing with steam.
(4) When cooking, try not to add water or add less water. When cooking, boil the water first, and then put the vegetables.