On which color of mung bean soup is more authentic, people in the north and south have something to say:
Southerners: Mung bean soup is naturally green!
Northerners: The mung bean soup I drank since I was a child was always red!
(Source: soogif)
So, what color is an authentic mung bean soup?
Stop the noise! The southerners are right, and the northerners are also right! Whether it’s red or green, it’s an authentic mung bean soup!
Red or green is not about mung bean, but mainly related to the process of cooking it.
(Source: soogif)
Mung bean is rich in polyphenols[1]. Polyphenols are very naughty and easily change color after being oxidized and polymerized. When the polyphenols of mung bean are oxidized, the color of the soup changes from green to red.
There are many factors that affect the discoloration of polyphenols. Water is a very important factor[1].
(Source: soogif)
Southern mung bean soup is more green, probably because the water is acidic and polyphenols are less oxidized, so that the soup retains the original green color of mung bean skin.
On the contrary, the northern green soup is slightly red, which may be because the water quality is alkaline, which accelerates the oxidation of polyphenols in mung bean skin.
(Source: soogif)
In addition to water, are there any other factors that may affect it?
1. Cook in a wok
Although iron ions can indeed undergo a complex reaction with flavonoids to make mung bean soup red[1], this requires a relatively high concentration of iron ions, and the iron pot at home does not May dissolve so much.
So,the wok is not the main factor that turns the soup red.
(Source: soogif)
2. Cover the pot
Oxygen is the factor that affects reddening. If you want to drink green mung bean soup, cover the pot and reduce the exposure to oxygen, which can slow down the oxidation of polyphenols in mung bean skin.
(Source: soogif)
3. Time
Studies have found that when mung beans are boiled in tap water, the first 4 minutes are green, and from 4 to 10 minutes, the green becomes red and gradually deepens. When using deionized water to cook mung beans, the green beans are always green for the first 10 minutes, and the green color is also deepened [2].
So, cooking time may not be the main factor affecting the color of the soup.
(Source: soogif)
For the dissolved polyphenols (such as: flavonoids[1]) in soup, research has found that the more yellow and green mung bean soup is, the higher the phenolic content is. The antioxidant capacity is also stronger[2].
(Source: soogif)
That is, in terms of antioxidant properties, green is better than red.
Of course it can’t reach the level of affecting health. After all, mung bean soup is mainly to add water. You can drink whatever color you encounter.
(Source: soogif)
If you have an obsession with green, green mung bean soup is a must, here are 6 tips.
1. Boil with pure water
2. Add lemon juice or white vinegar to the tap water
3. Don’t add caustic soda (baking soda) to make it worse [2]
4. Do not add white sugar while cooking[2]
5. After the water boils, add mung beans
6. It is best to cover the pot
(Source: soogif)
It is indeed a bit troublesome. As mentioned earlier, except for the color, red mung bean soup and green mung bean soup have similar nutrition. It is good to be a lazy person, drink whatever you have.
How can mung bean soup be healthier?
Mung bean soup is more important than red and green.
1. No or less sugar
2. Some people drink less
Old and young people with weak digestive function, people who are prone to abdominal distension and diarrhea
3. Try to do it yourself
4. If you can’t drink it within two hours after cooking, it should be sealed and refrigerated in time.
5. Eat both soup and beans
What color is your mung bean soup?
Let us know in the comments!
Reviewer: Zhang Yan| Associate Researcher, Institute of Nutrition and Health, Chinese Center for Disease Control and Prevention
Contributing Author: Pingping Liu| Registered Dietitian
References
[1] Chen Ran, Wang Jing, Wan Haijing, Zhao Jianjing, Fan Zhihong. Effects of cooking water pH and metal ions on mung bean clear soup [J]. Food Science, 2014, 35 (03):96-99.
[2] Chen Ran, Zhao Jianjing, Fan Zhihong. Effects of cooking conditions on the color and antioxidant activity of mung bean clear soup [J]. Food Science, 2012, 33(08): 115-120 .
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