Introduction: Research has shown that the stronger the antioxidant capacity of the bean soup, the better its heat-relieving effect. However, many people find that mung bean soup changes color easily. It is a vibrant green when first cooked, but turns red shortly after being poured out.
Objective: As the intense heat arrives, many people choose to drink mung bean soup to relieve summer heat. Research indicates that bean soup with stronger antioxidant properties is more effective at cooling down. However, many people notice that mung bean soup discolors easily, starting as a vibrant green soup that turns red not long after being poured. What is the difference in heat-relieving effects between red and green bean soup? This experiment measured the antioxidant properties of differently colored bean soups and also investigated methods for preventing discoloration when cooking mung bean soup.
Method: Using mung beans as the raw material, with a bean-to-water ratio of 1:10, the beans were boiled for 10 minutes with the lid on. First, the antioxidant properties of both green and red bean soup were measured. Subsequently, mung bean soup was cooked using tap water, mineral water, purified water, and distilled water. Finally, tap water was adjusted to different pH levels to cook the bean soup.
Results: 1. The antioxidant results showed that the red bean soup had significantly lower antioxidant capacity than the green soup. The redder the color, the lower the antioxidant capacity, meaning the heat-relieving effect of green bean soup is better than that of red bean soup.
2. Mung bean soup cooked with different types of water had different colors. The soup made with distilled water was the greenest and remained so for a long time. It was followed by purified water and mineral water. The mung bean soup cooked with tap water changed color the fastest, becoming noticeably darker almost every minute after exposure to the air, quickly turning red.
3. The pH level greatly affects the discoloration of the soup. Acidic tap water resulted in very little color change after cooking, while slightly alkaline tap water caused the soup to discolor very rapidly.
Lab Recommendation: It is best to cook mung bean soup directly with purified water. If not available, simply add half a spoonful of white vinegar or half a spoonful of lemon juice to the water, but be careful not to add too much. The specific method is to first bring the water to a boil, then add the mung beans, cover, and continue to simmer on low heat for 8-10 minutes. Pour out the clear broth. This method allows the mung bean soup to maintain its vibrant green color for a longer period in the air and has a good cooling effect. The remaining beans can be further cooked into mung bean paste or added with rice to make mung bean porridge.
Additionally, it is important not to add alkali when cooking mung bean soup, as this will not only significantly reduce its heat-relieving effect but will also severely destroy the rich B vitamins in the mung beans. (Food and Nutrition Research Laboratory, China Agricultural University)