Dark Mysteries on the Dining Table:

A vital grain crop

The Ministry of Agriculture’s Tainan District Agricultural Research and Extension Station (Tainan DARES) has been researching soybeans for over 50 years. Director Lo Jeng-chung tells us that the roots of soybeans form nodules which serve to fix nitrogen. When grown in rotation with rice, soybeans help increase nitrogen and organic matter in the soil, reducing the need for chemical fertilizers.

With an eye to food security, 13 years ago the government began to encourage domestic production of soybeans, wheat, and maize to replace foreign imports. Lo says that farmers who convert their crops to soybeans can be awarded grants of NT$60,000 per hectare. These soybean plantations are mostly in Chiayi, Tainan, Pingtung, and Hualien, occupying at least 4,400 hectares in total.

Black soybeans are an important grain crop. The yields of Taiwan’s black soybean cultivars amount to 3,000‡3,500 kilograms per hectare, more than those in other countries at the same latitudes. Taiwanese black soybeans also contain higher amounts of protein and are fresher and more aromatic than imported ones.

A black soybean protein drink.

Tainan DARES is devoted to promoting domestic black soybeans by developing black soybean products and transferring the technology to the private sector.

Native cultivars

Wu Chao-hui, a former researcher at Tainan DARES, has bred highly productive black soybean cultivars. Her Tainan No. 3, for example, is the most extensively grown black soybean variety in Taiwan. The farmers’ associations in Chiayi’s Xingang Township and in Tai­nan’s Xiaying District have both used their own Tainan No. 3 soybeans to produce soybean tea and soybean meal for sale.

Wu spent ten years breeding Tainan No. 11, a descendant of Tainan No. 3. This prolific cultivar bears big beans, is resistant to powdery mildew, and is especially suitable for roasting. It is now grown on 18 private farms, with a total area of 30‡40 hectares. Unlike Tainan Nos. 3 and 11, which have green kernels, Tainan No. 8 is yellow inside. The beans are large and have a satisfying mouthfeel; they can be processed into candied beans and amanatto, a Japanese confection. Tainan No. 8 can yield up to 3,870 kilograms of soybeans per hectare, weighing 49 grams per 100 beans.

“Despite their color, black soybeans are averse to too many hours of sunlight,” says Huang Han-ling, an assistant researcher at Tainan DARES. Accordingly, the researchers there aim to breed high-yielding cultivars that grow best in the moderate sunshine of January and February.

A company has acquired the technology from Tainan DARES to produce sweet, fragrant puffed black soybeans.

Soy sauce in a black bottle

With much to recommend them, black soybeans are nevertheless inexpensive. At home, we can use them to make soy milk, sweet tofu pudding, candied beans, and black-bean rice. They’re also a vital ingredient for fermented products. The soy sauce made from them is rich, aromatic, and silky smooth. Tainan No. 5 is ideal for soy sauce.

Lai Yingxiu, fourth-generation owner of Yong Xing Soy Sauce in Tainan’s Houbi District, says that Tainan No. 5 has a thin hull and is very fleshy. The soy sauce made from this cultivar has a quietly refined flavor, and contains more nitro­gen than that made from imported soybeans, indicating a greater abundance of amino acids converted from proteins. Taiwan’s native Heng­chun black soybeans have thicker hulls, exuding a wild charm. When fermented, they give off a stronger aroma.

Ascending to the top floor of Yong Xing, we find ceramic vats neatly laid out across a broad, airy space. The strong smell of soy sauce pervades the air. Lai explains that these vats have to be exposed to the elements for four to six months. Opening a vat of sauce that has been left fermenting for three months, she tells us: “As the antho­cyanidins in the seed coats of Tainan No. 5 dissolve, the beans become more and more brownish red, while the sauce turns darker and darker. When mature, the soy sauce will have a sweet aftertaste.”

Over time, the fermentation of black soybeans gives the sauce its characteristic shimmering amber color. You really have to taste it to know what that intoxicatingly rich aroma is like. As old Taiwanese wisdom has it: “soy sauce in a black bottle”—you can’t judge a book by its cover.

Yong Xing uses Tainan No. 5 and Hengchun black soybeans to produce its rich, aromatic soy sauces.

Health benefits

According to modern research, black soybeans are rich in vitamins and antioxidants, including isoflavones, anthocyanidins, and polyphenols. Chen Hsiao-ching, an associate researcher at Tainan DARES, points out that the absence of genetically modified varieties of black soybeans means that there are no GMO-related controversies surrounding them. Taiwan’s locally produced black soybeans are fresh and can be used to develop health products. While investigating their health effects relevant to patients with metabolic syndrome, Chen found that black soybean protein powder could help reduce body fat. The small protein fragments produced through enzymatic hydrolysis, which are easier for the body to absorb, may be especially beneficial to elderly people who suffer from abdominal bloating after drinking soy milk.

Tainan DARES has since developed products such as black soybean peptides, and has transferred the technology to the private sector. One company is producing black soybean protein drinks, collaborating with practitioners of traditional Chinese medicine to use these as meal replacements in the treatment of metabolic conditions. Chen remarks with a smile: if adzuki bean essence has a market, why not black soybean essence as well? She has invented a ready-made black soybean drink. With other new products such as soy paste and oil in the offing, she aims to carry on promoting black soybeans as a marvelous food ingredient.