Buried Treasure:

Taiwan’s Black Peanuts and Truffles

Cindy Li　/　photos by Kent Chuang　/　tr. by Phil Newell

October 2024

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Dark-colored “Black Diamond” peanuts are a gift from Heaven to Yuanchang Township in Yunlin County.

Whether it be “Black Diamond” peanuts, which have purple or black skins and are known as a Taiwanese specialty, or Taiwanese truffles, whose commercialization is still in its infancy and awaits the commitment of more resources, both are examples of dark “buried treasure” nurtured by the soil of Taiwan.

Opening the shells of black peanuts, there is a sharp contrast between the coal black of the nuts and the tan color of the shell.

Black Diamond Peanuts:Heaven’s Gift to Taiwan

The poem “Peanuts” by the Taiwanese poet Chen Jinpo reads: “They are turned into oil to fill lamps / And are always enjoyable with a goblet of wine.” The peanut, also known as the “long life nut,” is a popular snack food in Taiwan and formerly was pressed for its oil to light lamps. The poem vividly depicts such scenes of everyday life.

The most commonly grown type of peanut in Taiwan is the “oil peanut,” with light brown or flesh-colored skin. Other varieties include red, striped, and “Black Diamond” peanuts; the latter are so dark that they seem to shine.

At 80 years old, Wu-Zhang Gongli, known as “the grandmother of Happy Peanuts,” still picks out premium quality peanuts by hand as seed for future crops.

God’s gift to Yuanzhang

Searching for the origins of Black Diamond peanuts, we come across many different versions of events. Chen Kuo-hsien, a researcher at the Tainan District Agricultural Research and Extension Station who has been studying peanuts for many years, says that one of the more trustworthy stories has it that when farmers in Yunlin County’s Yuanzhang Township were cultivating striped peanuts, they discovered some black-skinned nuts among them, and out of curiosity they deliberately held back this gift bestowed upon them by Heaven to use as seeds, turning their hometown into “the home of Black Diamond peanuts.”

There is a widely held folk belief that in terms of traditional Chinese medicine, black foods tonify the liver and kidneys and nourish the body’s yin and the five zang organs (heart, liver, spleen, lungs and kidneys). This lends extra value to black peanuts. In fact, there is some scientific evidence for this belief. Chen Kuo-hsien notes that the dark-colored skins of black peanuts, like certain vegetables and fruits such as black soybeans and grapes, contain large amounts of natural anthocyanidins, while the nuts themselves are replete with other ingredients that are beneficial to health including eight essential amino acids, vitamins B6, B2, and B1, and niacin.

Fragrant, crunchy, and addictive black peanuts first came onto the market in 2010, and immediately became a popular option for people to give as gifts.

Bright little peanut flowers adorn the glossy green peanut plants.

Special attention required

Walking through the fields of Yuanzhang, everywhere you can see scenes like those depicted in Chen Jinpo’s poem: “The ground is thickly carpeted with green leaves / Whole fields are filled with yellow flowers that look like butterflies.” In recently planted peanut fields one can see pretty little yellow flowers everywhere amidst the green buds. Wu Qilu, the founder of the Happy Peanuts brand (now run by his sons Wu Wenqin and Vincent Wu), says that the flowering period is a time when peanut farmers must pay special attention.

Peanuts, known in Chinese as “sinking nuts” and also in English as “groundnuts,” get these latter names because after the blooming, pollination, and withering of the flowers, the gynophores—short stalks at the bases of the ovaries—elongate to form threadlike structures known as pegs that carry the fertilized ovules into the ground, where they develop into the seeds—the peanuts—with which we are so familiar. During this period the plants need more nutrients, which is why most farmers apply additional fertilizer at this time to help the peanuts mature.

In contrast to the growth period of 90‡100 days required for oil peanuts, black peanuts need 110‡120 days. During this time not only must farmers continue to apply various kinds of fertilizer, they also must pay special attention to the height of the stems and leaves above ground to ensure they do not grow too vigorously and thereby draw nutrients away from the peanuts growing beneath the soil.

In addition, in recent years climate change has blurred the distinctions between the seasons and there are frequent episodes of extreme heat, which leads to the issue of unpredictable germination. Wu Wenqin explains that sprouted peanuts do not have the same problem as potatoes, which can be toxic after sprouting, but the texture can be somewhat less pleasant than that of ungerminated fresh peanuts.

Wu Wenqin (right) and Vincent Wu (left) are the second generation who have taken over the family business from father Wu Qilu (second right) and mother Wu-Zhang Gongli (second left). Together they have built the Happy Peanuts brand, and continue to develop sales channels in the hopes that even more people will learn about black peanuts.

A warm feeling with a “black heart”

As Chen Jinpo expressed in his poem: “I love late-autumn days when the pods are harvested / And the peanuts leave a fragrant taste in the mouth.” Whether one is talking about peanut candy, peanut soup, or the peanut kernels found in zongzi (meat dumplings), peanut-enhanced foods, whether sweet or savory, are invariably mouthwatering.

However, when black peanuts are included in a dish, there is a risk that their anthocyanidins, which are soluble in water, will tint the food black. For this reason, Black Diamond peanuts are most commonly sold still in the shell.

Freshly harvested peanuts must first be sun-dried for about ten days. At harvest time the peanuts are laid out on the roads beside the fields, forming majestic “peanut boulevards.” “You can’t simply leave the peanuts lying out in the sun; they have to be turned over at least twice a day, and more diligent farmers will turn them every two hours,” says Wu Wenqin, adding that sun-dried black peanuts have a crisper texture that machine-dried peanuts just can’t match. After sun-drying, the Wus remove impurities and select and grade the nuts before roasting them in a rotating drum with iron pellets. Wu notes that this method beautifies the shells and ensures that the peanuts get evenly heated.

Every “black-hearted” Black Diamond peanut produced by Happy Peanuts is the product of the dedication of three generations of the Wu family, as well as their sincere devotion to preserving the black peanuts of Yuanzhang Township.