1. Why "Bean Sprout" Is Not the Name of a Plant
There is no plant called the "bean sprout plant." For carrots, there is a carrot plant; for radishes, there is a radish plant. However, dictionaries define bean sprouts as seeds from beans or grains that have been made to germinate and grown. [1]
The name is said to come from the Japanese verb moyasu, meaning “to make sprout.” Bean sprouts are vegetables grown by people making seeds germinate in the dark. Growing them without light is called "softening cultivation." [2] Because the type of seed changes the result, the most common bean sprout you see must come from a specific bean. What is that bean?
2. Which Beans Are Used to Make Bean Sprouts, Mainly the Mung Bean
The main ingredients for bean sprouts are soybeans, mung beans, and black gram (also called black mung bean). Sprouts can also be made from azuki beans or buckwheat. [2] However, the mung bean sprout is the most widely distributed in Japan. [1] Black gram sprouts are said to be slightly thinner, while soybean sprouts are often sold with the bean still attached. [1]
The mung bean is originally from India, with the scientific name Vigna radiata. In Japan, it is stated that nearly all mung beans used for sprouts are imported from overseas. [3] A 2012 article also noted that Japan relied on imports from China and other countries for almost all the mung beans it consumed. [4] These small beans, born in India, cross the sea to arrive in Japan. How do they become the long, thin sprouts in the bag?
3. How Bean Sprouts Are Grown in the Dark for About One Week
For home growing, one method suggests soaking seeds in water overnight, placing them in a spot where no light enters, and washing them three times a day. This is repeated for 7 to 10 days. [6] Another example suggests soaking beans in ten times their volume of water overnight, placing them in a well-ventilated, dim room, and rinsing them about twice a day. [2] While the number of washings differs, the common points are maintaining water, darkness, and moderate temperature for about a week.
As a guide for harvest, it is said that sprouts are ready when the part between the bud and the root (the hypocotyl) has grown to 5 cm (about 2 inches) or more. [2] In factories, water and temperature are managed in light-proof environments, and harvesting takes about one week. [5] So, in a place without light or soil, they grow to over 5 cm in about a week. Have they always been eaten this way?
4. How Bean Sprouts Were Used as Medicine or Brewing Ingredients in the Past
In the Heian period book *Honzo Wamei*, bean sprouts were listed under the name "Moyashi." In the Edo period book *Wakan Sansai Zue*, they were introduced as something with medicinal effects. Thus, in old books, they were sometimes introduced as medicine. [2]
In the Heian period dictionary *Wamyoshō*, the character for "sprout" was read as "rice sprout" and used to make soy sauce-like products. There was also "barley sprout," used for making sake and medicine. [1] The "sprouts" in old documents sometimes refer to things different from today’s bean sprouts. Eating bean sprouts as a vegetable is considered a relatively new practice. [1] When did they become a vegetable?
5. When Bean Sprouts Became an Everyday Vegetable in Japan
In 1842, the Toyama domain is said to have banned the sale of bean sprouts because they were seen as leading to luxury. [2] There is an explanation that edible bean sprouts spread to Edo from cultivation methods introduced in Nagasaki after 1850. [2] It is said that their widespread use as a vegetable began after the Meiji period. [2]
This history comes from a single source, so it should be read with some caution. However, it is an interesting contrast that bean sprouts, now known as a cheap vegetable, were once considered "luxury." A major shift is visible: from medicine and brewing ingredients, through a period of being seen as luxury, to a daily cheap vegetable. [2] What is happening to the price of the beans that support this cheap vegetable?
6. Why Cheap Bean Sprouts Depend on the Price of Imported Mung Beans
According to a December 2012 article, Japan relied on imports from China and other countries for almost all the mung beans it consumed. In that year, a domestic company started growing mung beans in Bangladesh to broaden supply sources. [4]
According to a producers' group, the price of Chinese mung beans became about 3.5 times higher in 2021 than in 1995. They say this rose due to rising labor costs in China and bad weather since 2010. [5]
This 3.5 times increase is the price of the mung bean itself, not the price of bean sprouts in stores. Reports mention examples of bean sprout farmers shipping one bag for about 26 yen. [5] It can be understood that even when raw material prices rise, it is difficult to raise the selling price. The price of imported beans is connected to the cheap bean sprouts. Here is a way to check this at home.
7. How to Measure Bean Sprout Growth for One Week in Your Kitchen
Try measuring the growth every day. Soak bean sprout beans in water overnight, place them in a spot where no light enters, and wash them three times a day. [6] Keep the container clean and change the water frequently. When eating, wash them well before eating, with an adult. [6]
At the same time each day, use a ruler to measure the length of the longest bean sprout. The materials say 5 cm (about 2 inches) is a guide for harvest. [2] Record on which day your sprouts exceed 5 cm to compare with the "7 to 10 days" guide using your own numbers. [2]
Are there days when growth is fast or slow? Does changing the number of washings make a difference? Many questions can be tested at home. If eating them, check health precautions with an adult. [6]