Can anyone help me see if this bowl is red bean soup or mung bean soup?

The answer is: mung bean soup!

Mung bean soup, known as the "life-saving soup" of summer, is the favorite summertime delicacy. A bowl of cold mung bean soup can not only bring coolness, but also soothe people's hot mood. However, the color difference of mung bean soup has aroused heated discussions: Why does the soup made of mung beans turn red in the end?

01 The mystery of why mung bean soup turns red

The polyphenols in mung beans will show different colors in different acidic and alkaline environments . This is one of the scientific principles for the color difference of mung bean soup.

In fact, the final color of mung bean soup is affected by many factors.

Image source: Photo Network

1) Impact on water quality

Water can be either acidic or alkaline, and this difference in acidity and alkalinity may cause changes in the color of mung bean soup. In an acidic environment, more polyphenols in mung beans are dissolved and are more stable, while in an alkaline environment, these polyphenols are easily oxidized, making the mung bean soup appear red.

2) Placement time

After the mung bean soup is exposed to the air for a period of time, the polyphenols on its surface easily react with oxygen, causing oxidation and discoloration . Therefore, if the mung bean soup is not drunk immediately after it is cooked, but left for a period of time, it is likely to gradually turn red.

3) Choice of cooking utensils

When using an iron pot to cook mung bean soup, the iron element may react with the polyphenols in the mung beans , causing the soup to turn red. Cooking utensils made of non-metallic materials such as stainless steel or ceramic generally do not produce such reactions.

4) Covering the pot or not has little effect

In theory, covering the pot can reduce the contact between the mung bean soup and the air, thereby slowing down the process of oxidation and discoloration. But in reality, the effect of this method may not be obvious , because the mung bean soup will still be in contact with the air in the pot during the cooking process.

02 Is red mung bean soup still nutritious?

The color change of mung bean soup is mainly due to the oxidation of polyphenols, but this oxidation does not significantly change the nutritional value of mung bean soup.

Image source: Photo Network

It should be noted that the antioxidant effect of mung bean soup does decrease after it turns red . Antioxidants can protect cells from oxidative damage and help prevent a variety of chronic diseases. Therefore, although mung bean soup still has certain nutritional value and health benefits after it turns red, its original antioxidant efficacy will be affected. Despite this, red mung bean soup can still be eaten, but its antioxidant health effect is not as good as green mung bean soup.

03 How to cook mung bean soup in the healthiest way?

If you want to keep the delicious taste of mung bean soup without affecting its antioxidant effect, you can try this:

Choose a high-quality water source and fresh mung beans to make soup. When cooking mung bean soup, you can choose to use acidic water or add a small amount of lemon juice or vinegar to adjust the pH of the water.

It is also important to control the cooking time. Too long a cooking time may cause the loss of nutrients in mung beans. At the same time, avoid using cooking utensils such as iron pans that may react with polyphenols, and choose non-metallic cooking utensils such as stainless steel or ceramics.

Put the cooked mung bean soup into ice water or refrigerator as soon as possible to cool it down. This can reduce the occurrence of oxidation reaction and keep the green color of mung bean soup. If you need to store mung bean soup, it is best to seal it in the refrigerator to reduce contact with air.

Avoid using too much sugar and other additives. Adding white sugar or baking soda will reduce the antioxidant capacity of mung bean soup, while adding salt can slightly increase its antioxidant capacity. These additives affect the antioxidant activity of mung bean soup by interacting with phenolic substances.

Add synergistic ingredients to enhance the nutritional value of mung bean soup. For example, adding appropriate amounts of lily, lotus seeds and other ingredients can not only increase the taste level, but also nourish the lungs, clear the heart and calm the mind.

Image source: Photo Network

Although mung bean soup may lose some of its antioxidant effects in the process of turning red, its overall nutritional value is still high. Whether it is refreshing green or warm red, mung bean soup is an indispensable delicacy in summer.

Author: Wang Zhengyuan, PhD in Nutrition, Associate Chief Physician, Shanghai Center for Disease Control and Prevention

Planning & Editing: Tiara