How to cook green bean soup

The key to making mung bean soup green is to control the cooking time and pH level. The greening of mung bean soup is mainly related to the oxidation of polyphenolic substances in mung beans. Using methods such as cold water, reducing the number of times the lid is opened, and adding acidic substances appropriately can help maintain the green color of the soup. Green beans contain abundant polyphenol oxidase, which can easily undergo browning reactions under high temperature and oxygen, leading to a red soup color. Soaking mung beans in cold water and boiling them directly in a pot can slow down the activation rate of enzyme activity. During the cooking process, keep boiling on low to medium heat to avoid prolonged rolling and accelerated oxidation on high heat. The amount of water should be completely submerged in mung beans, with a ratio of about three times the volume of mung beans, to prevent rapid evaporation of water and excessive local temperature. Adding a small amount of white vinegar or lemon juice can lower the pH value of the soup, and an acidic environment can inhibit polyphenol oxidase activity. But the amount of acidic substances added should not be too much. It is recommended to add 1-2 teaspoons per 500 grams of mung beans. Using clay or glass pots is more beneficial for maintaining the color of the soup than metal pots, as metal ions may catalyze oxidation reactions. The cooking time should be controlled at 30-40 minutes, excessive boiling will cause chlorophyll decomposition. After cooking, take it out in a timely manner to avoid darkening the color due to prolonged insulation.

It is recommended to use fresh and plump mung beans when cooking green mung bean soup. Old mung beans are difficult to maintain their emerald green color due to their high degree of oxidation. Before cooking, rinse the surface impurities repeatedly with clean water, but do not soak for a long time to prevent nutrient loss. In summer, mung bean soup can be naturally cooled and stored in a refrigerated environment to delay oxidation and discoloration. When drinking, it is recommended to consume it in moderation according to one's constitution. For those with spleen and stomach deficiency and cold, it is recommended to pair it with ginger slices, which can neutralize coldness and help with digestion and absorption. Green beans should be stored in a cool and dry place for daily preservation to prevent moisture and deterioration, which may affect the cooking effect.