Sihaiwang: mung bean soup, I think everyone has drunk it. The ingredients are very common and can be made at home. But some people will have a question, why is the mung bean soup green outside and red at home? Why on earth is this? Can red mung bean soup drink after all? Is it poisonous?
Can I have the boiled green bean soup
Mung bean soup can be drunk when it turns red.
Mung bean soup can be eaten after it turns red, which has no toxic effect. It is only because the active ingredients of mung bean are mainly polyphenol antioxidants. If the cooked mung bean soup turns red, the effect of heat elimination is not good, and the nutrients are not so comprehensive, but it does not affect the consumption.
How to cook mung bean soup is green
There are a lot of polyphenols in mung bean skin. As long as they are exposed to oxygen, they are very easy to oxidize into quinones, and continue to aggregate into darker substances. Therefore, when boiling mung bean soup, the pot cover should be covered to minimize the contact area between mung bean and oxygen and avoid oxidation.
2. It's not easy to change color when boiled with pure water
The food nutrition research office of China Agricultural University used tap water, mineral water, purified water and distilled water to boil mung bean soup. The results showed that the color of mung bean soup was different. Distilled water is the greenest color and remains the same for a long time. Next are pure water and mineral water. The color of mung bean soup boiled in tap water changes the fastest. It becomes dark and red in almost every minute after contact with the air. Therefore, it is best to boil mung bean soup with pure water.
3. A few drops of lemon juice keep mung bean soup green
It was found that acidity and alkalinity can also greatly affect the discoloration effect of decoction. The tap water in the north is alkaline water. The color changes very fast after boiling mung bean soup. After pouring out mung bean soup, you can see the obvious color change within two minutes. But when vinegar or lemon juice is added to the tap water, the color of the soup changes little. Therefore, if you boil mung bean soup with tap water, you can add half a spoon of vinegar into the water, or squeeze in a few drops of lemon juice, but pay attention not to add too much, otherwise the soup will become sour, affecting the taste.
4. Add mung beans to boil for 8 minutes
The best way to cook mung bean soup is to boil the boiling water first, then put in mung bean, continue to cook for 8-10 minutes, then pour out mung bean soup. At this time, the color of the soup is green, and the dissolved substances are mainly the active ingredients in the bean skin, and the oxidation degree is the lowest, and the heat clearing ability is the strongest. After pouring out the soup, the rest of the beans can continue to be cooked into mung bean paste, or add rice to make mung bean porridge.
Why is the mung bean soup red when boiled? 1. It is oxidized in the air
The newly boiled mung bean soup is green. It turns red after a period of time, which is a normal phenomenon. The principle of reddening is very simple. It is the result of oxidative polymerization of phenols partially dissolved from mung bean skin in mung bean soup under the action of oxygen in the air. So, that's why it's easy to change color when cooking mung bean porridge with open lid, but it's not easy to change color when cooking mung bean porridge with pressure cooker.
2. Boil with tap water containing alkali
In fact, mung bean soup can be put for a long time without discoloration. The secret of the problem is that the water for cooking beans is different. Using tap water, mineral water, purified water and deionized water respectively to cook mung bean soup, the result is that the color of deionized water is the greenest, and it will not change for a long time. The color of mung bean soup boiled in tap water changes the fastest. It becomes dark almost every minute after contact with the air, and soon turns red. Obviously, it is caused by different water quality. The tap water in the north is alkaline water. It changes color very quickly after boiling mung bean soup.
3. Cook with edible alkali
When the mung bean soup is boiled, if the edible alkali is put in it, it will also have a reaction, generally showing red. The purpose of alkali release is to make the beans easy to rot, but it will lose the nutrition of the beans and turn red easily. If you want to make it a little sticky, consider adding a small amount of oatmeal or glutinous rice to thicken it.
4. Iron utensils for mung bean soup
Cooking mung bean soup in an iron pot or stir well with an iron spoon can also cause discoloration. Most of the active components of mung bean are in mung bean skin. After the action of flavonoids and metal ions in mung bean skin, it may form a darker complex, which makes the color of mung bean soup red and black. In this case, it is better not to drink the chameleon mung bean soup, which will cause gastrointestinal discomfort and dyspepsia after consumption.
Therefore, do not use iron pot to cook mung bean soup. It is good to use casserole or stainless steel pot. At the same time, don't use iron spoon when stirring. Just use the spoon brought by the rice cooker to stir.
5. Making mung bean soup in cold water is easy to turn red
Mung bean skin contains a lot of polyphenols, as long as they see oxygen, they will change color. When boiled in cold water, it takes a long time, oxidizes quickly, and the soup changes color more easily.
6. When the water is less and cold water is added halfway, the color will change easily
When cooking mung bean soup, some people find that their water is less and they are almost dry, so they choose to add cold water halfway. This is wrong. Add cold water. The mung bean soup in the pot is easy to change color when exposed to oxygen. Even if you want to add, you should also add boiled water.