1. Vegetables are green, white, black, yellow and so on.
2. After frying, coloring, smoking and other processing, new colors are produced.
3. Use the color of condiments (such as soy sauce, sugar, red oil, etc. ).
4. Use the colors of vegetables to cooperate with each other to form a composite color. How to ensure health and nutrition and keep the bright color of vegetables through cooking is a subject that needs to be studied.
Fresh vegetables are easy to fade during storage and cooking, because the stability of natural pigments in vegetables is poor, especially leafy vegetables, which have high chlorophyll content but are unstable, afraid of light, heat and oxygen. There are three conditions that can change the color of vegetables, one is oxygen, the other is polyphenol oxidase, and the third is polyphenols, which are collectively called enzymatic browning. In order to prevent browning, cut vegetables that change color easily are often soaked in cold water to isolate them from oxygen in the air, so that they will not change color. Dealing with the discoloration of vegetables in this way is also called soaking for oxygen isolation.
The reason why potatoes change color is because they contain a kind of phenol oxidase, which will react chemically under the action of oxygen to turn potatoes brown. Cut potatoes will not change color if they are put into clear water in time. In terms of nutrition, many vegetables treated by knife workers should not be soaked in clear water, which will cause the loss of nutrition. But for potatoes, if they are not soaked in water after knife treatment, the color will change after a period of time, and the effect is not good after cooking.
Onion is discolored because it contains a substance called flavone. When heated with metal tools such as iron and aluminum, it will generate brown, blue and black complexes, which will make the copied onion opaque and affect the color of dishes. The solution is to mix chopped onion with a little flour to make it stick to the flour evenly, and it will not change color after cooking, because mixing onion with flour can avoid the direct contact of flavonoids with iron, aluminum and so on.
The color of carrots is the most stable among vegetables, so only by shortening the cooking time can the color and nutrition of carrots be maintained.
Lotus root will be oxidized to black when exposed to air, because its tissue contains flavonoids and polyphenol oxidase. In order to prevent lotus root from discoloring, it can be scalded with waste water 10 second after changing knives (the time should not be too long, because polyphenol oxidase is not heat-resistant, and it can be inactivated in 10 second).
Some white vegetables, such as cabbage, cabbage, cauliflower, etc. Contact with alkaline substances must be prevented. In addition, excessive cooking should be prevented. A small amount of vinegar can be added to blanching water, which is beneficial to prevent discoloration and make vegetables hard and straight.
Eggplant should be waterproof when stored. Eggplant will rot after being soaked in water for a while, because the eggplant skin is waxy, it will be destroyed when it is soaked in water, and the eggplant meat will rot. Purple eggplant will be more colorful after being washed and cooked with proper amount of alum.
Cooking and heating have the greatest influence on vegetables. In order to shorten the heating time, colorful vegetables are often cooked quickly and can be cooked two or three times. Because the same raw materials are also old and tender, such as fried shredded pork with leeks, first fried shredded pork to taste, then fried leek roots in the first half, and fried leek leaves in the second half after six ripens, so the heat lasts for a long time and the color remains green after treatment. For example, stewed kidney beans with sliced meat are relatively green. You can fry kidney beans with oil instead of water. After frying kidney beans into green, add soup to stew for a while, so that the stewed kidney beans are crisp and can not change color for a long time.
For blanched and fried vegetables, the method of using oil can keep the color better than blanching with water, and can keep it unchanged for a long time. The main reason is that oil has high temperature and certain viscosity, which can make the water in green tissue cells evaporate quickly, make the raw materials permeable and form a dense oil film on its surface, weaken the oxidative discoloration and loss of green substances, and prolong the color degradation.
It is difficult to keep the color of vegetables when cooking cauldrons. There are three difficulties: first, fried vegetables can't be packaged immediately, and it takes a while to finish, and vegetables, especially green leafy vegetables, are easy to change color; Second, the number of vegetables invested at one time is large, so it is difficult to blanch; Third, color is difficult to master. How can we respond more effectively? From the experience, we can do it according to the following points: first, fry the vegetables that are easy to change color until the end, and fry the vegetables that are not easy to change color first; Second, don't be afraid of trouble. If the food is large, you can fry it two or three times.
When cooking, especially vegetables, it is best not to put soy sauce, but to adjust the mouth with salt. You should also master the salt and adjust your mouth before taking out the spoon. At the same time, it is also a powerful measure to ensure that dishes do not change color. Oil can also add flavor and luster to vegetables and prevent green vegetables from turning yellow.
For some pickled vegetables, such as pickled cucumber, pickled radish, pickled potherb mustard, etc. In the curing process, it will also change color, making the product turn gray and yellow. In order to prevent discoloration, the pickled products can be soaked in a small amount of lime water for 5 minutes to make the raw materials alkaline, and then pickled with coarse salt, because coarse salt contains magnesium, which can avoid the raw materials from producing too much acid, which not only has antiseptic effect, but also can prevent the pickled vegetables from discoloring. Pickling time should not go through the motions, but should be preserved at low temperature, which is also an important factor to prevent pickles from discoloring.
Red heart radish mixed with rice vinegar will make radish more colorful. This is because red radish contains a water-soluble pigment called anthocyanin, which turns red when it is acidic and blue when it is alkaline. Therefore, adding vinegar when making red radish will make the product more brilliant. In addition, when mixing vegetables, you can put salt and monosodium glutamate first, then put oil and mix well, so that vegetables will not change color in a certain period of time. Many vegetables are often blanched. A small amount of vegetable blanching can generally be mastered well, but a large amount of blanching is not easy to master, so we need to pay attention to several points.
First, open the pot cover during heating. The reason is that when vegetables are exposed to high temperature, the green color of vegetables will increase and become green. For example, if heating continues, green will turn yellow or brown. This is because the magnesium removal reaction of chlorophyll occurs, especially in acidic environment, which is more likely to occur. Organic acids are released during the heating process, and organic acids are the main substances that promote the discoloration of vegetables. Opening the pot cover can make the organic acid volatilize with the steam, thus reducing the process of magnesium removal from vegetables.
Second, you should also pay attention to the fact that the drowning time should not be too short. Some vegetables are not cooked thoroughly because the metabolism of these fresh vegetables is still going on before heating. If the blanching time is too short and the blanching of vegetables is not complete, it will not only fail to inactivate the phenolase, but will promote the browning of vegetables.
Third, the blanching time should not be too long, too long will make vegetables dull. In the past, there was a way to increase the greenness of vegetables, that is, adding alkali or soda during blanching, but it also destroyed the nutrition of vegetables accordingly.
Fourthly, if vegetables are not soaked in cold water immediately after blanching due to some objective reasons, appropriate amount of oil can be added immediately when blanching, so that the oil can be quickly wrapped around the vegetables to prevent water from contacting the vegetables, reduce nutrient loss and keep the vegetables from oxidation and discoloration for a long time.
Fifthly, vegetables with special smell and easy to decolorize should be blanched separately to avoid cross-talk dyeing. In addition, white vinegar and salt can be added to the water when blanching vegetables, which can make blanched vegetables brighter.
Sixth, when blanching, the amount of water is large, which is generally 5 to 7 times that of raw materials. If the amount of water is too small, the temperature of vegetables will drop rapidly after cooking, which will affect the color of vegetables.