From Famine Food to Trendy Snack:

Sweet potatoes have been listed by the World Health Organization among its “top ten vegetables.” Elongated varieties of sweet potato resemble the island of Taiwan in shape, while the plant’s resilient vitality enables it to flourish in inhospitable environments. Thus it is also used to describe Taiwan’s spirit of resilience and vitality.

Different generations of Taiwanese have different memories of sweet potatoes. Elderly folk now in their 70s and 80s remember eating them shredded in congee, or cut into chunks, and they were considered an “inferior food” that was symbolic of poverty.

For people now in the prime of life, in their 30s to 50s, cooking sweet potatoes in “clay ovens” was a common practice. This generation also often saw street vendors hawking the tubers to the sound of a bamboo cog rattle. They were also used in making pastries and snacks such as candied sweet potatoes and sweet potato cookies.

In recent years, amid the trend towards healthy diets, sweet potatoes have been found to be rich in nutrients and are now seen as a superfood. They have also become popular among younger people as an alternative staple food sold in convenience stores. Meanwhile, businesses have developed processed products, turning sweet potatoes into a material for creative cuisine. This fashionability has transformed their past image of being a cheap, low-grade food.

Sweet potatoes are an indispensable classic food for clay ovens.

A weapon against the Dutch

Academic research reveals that the sweet potato was introduced into Taiwan artificially. In his book The Trace of Taiwan Sweet Potato, Tsai Cheng-hao, an associate research fellow in the Department of Painting, Calligraphy, Rare Books and Historical Documents at the National Palace Museum, sets out the genealogy of this tuber. The modern sweet potato originated in Central or South America, and the explorer Columbus is thought to have started sweet potatoes on their worldwide journey. While in 16th-century Europe they were only for the elite, today sweet potatoes are cultivated widely in tropical, subtropical, and even temperate regions, and have become a global product.

There are many theories as to how sweet potatoes were introduced into Taiwan. One says they were brought by immigrants from China, but Tsai Cheng-hao says it is also possible that they were brought to Eastern Taiwan from the Philippines. Chinese traveler Chen Di, writing in the early 17th century, was the first to report that sweet potatoes were grown in Taiwan.

Sweet potatoes played a critical role in the invasion of Taiwan by Zheng Chenggong (Koxinga) to expel the Dutch. Tsai says that when Zheng crossed over from China he did not bring enough grain with him, so he requisitioned sweet potatoes from the people of Taiwan and dispatched troops to clear new land to grow them. It was thanks to these adequate supplies that he was able to defeat the Dutch. Because of Zheng, sweet potato cultivation spread across Taiwan and they were even exported to the Chinese mainland.

Lai Yung-chang, researcher and division director in the Department of Agronomy at CAEB, has been studying sweet potatoes all his life.

Plant breeding in the Japanese era

“Sweet potatoes didn’t taste good up to and during the era of Japanese rule,” says Lai Yung-chang, researcher and division director in the Department of Agronomy at the Chiayi Agricultural Experiment Branch (CAEB) of the Taiwan Agricultural Research Institute. Back then they were starchy with poor texture and were a choking hazard when consumed. Sweet potatoes were often used to feed pigs, and while their starch could be made into alcohol, this was not cost effective.

During the era of Japanese rule (1895–1945), the colonial authorities began a selective breeding program at Chiayi in order to improve the texture. Since then, CAEB has bred 74 varieties, while the Taoyuan and Hualien District Agricultural Research and Extension Stations have bred four varieties, each with different uses.

At present, the most popular varieties in the Taiwan market are Tainung No. 57 and Tainung No. 66. Tainung No. 57 has spindle-shaped tubers (thick in the middle with tapered ends), orange flesh, and a delicate texture; it is the most widely planted variety in central to southern Taiwan. Meanwhile, Tainung No. 66 is the most commonly cultivated variety in central to northern Taiwan. It has red-hued flesh, a high moisture content, and a soft texture. Tainung No. 73, bred by Lai Yung-chang, is rich in anthocyanidins, and has purplish-pink skin and purple flesh as well as an excellent mouthfeel; it adds color to Taiwan’s sweet potato spectrum.

The experimental farm at CAEB grows over 10,000 sweet potatoes annually, for use in the selective breeding of new varieties. (courtesy of CAEB)

The Tainung No. 66 sweet potato bred by the Taiwan Agricultural Research Institute is one of the best-selling varieties in the Taiwan market. (courtesy of CAEB)

The purple-hued Tainung No. 73 variety adds color to the spectrum of sweet potatoes in Taiwan. (courtesy of CAEB)

The Tainung No. 57 sweet potato has a fragrant sweetness and delicate texture, making it popular with consumers home and abroad. (courtesy of CAEB)

A major germplasm bank

The Root Crop Laboratory at CAEB, known as “the cradle of Taiwan sweet potatoes,” holds germplasm from more than 1,400 varieties of sweet potatoes, including varieties bred in Taiwan as well as overseas varieties transferred to CAEB from the World Vegetable Center.

In a tissue culture room next to the germplasm storage facility, virus-free seedlings are being propagated in order to reduce the incidence of sweet potato viruses.

Sweet potato leaves are commonly consumed as a vegetable in Taiwan. Lai Yung-chang explains that the sweet potatoes grown for their leaves and those grown for their tubers are different varieties. On a side note, Lai remarks that although Taiwanese often use the phrase “taro and sweet potatoes” to describe ethnic harmony in Taiwan, these two plants belong to different taxonomic families and cannot be hybridized.

CAEB’s sweet potato germplasm bank is larger than any in Southeast Asia, with more than 1,400 varieties.

Targeting international markets

In recent years the area cultivated with sweet potatoes in Taiwan has remained steady at between 9,000 and 15,000 hectares, with Changhua, Yunlin and Tainan accounting for two-thirds of the total cultivated area.

At room temperature, sweet potatoes can be kept for about two weeks before they sprout. Currently, exported sweet potatoes are mainly processed, but if businesses introduce cold chain technology, storage life can be extended to eight to ten months, ensuring year-round supply. This will reduce losses in storage and transport.

Yunlin County’s Shuilin Township has the largest area cultivated with sweet potatoes of any township in Taiwan, with farmers there mainly growing Tainung No. 57. In 2000 Su Yuanyuan, at that time chairman of the Qiongpu Community Development Association in Shuilin, persuaded his son Su Jiayi, head chef for Cantonese cuisine at a five-star hotel, to return home and develop recipes for sweet potato cuisine, in order to help farmers sell their sweet potatoes and raise their value-added.

In 2013, Su Yuanyuan founded a cooperative in Qiongpu that contracts farmers to grow sweet potatoes and has acquired both Traceable Agricultural Product (TAP) and Global Good Agricultural Practice (Global G.A.P.) certification. Su Jiayi is responsible for food product R&D and processing, and the products are sold under the “Uncle Sweet” brand name. They have established a comprehensive industrial value chain comprising cultivation, cold chain logistics, processing, and marketing. Their goods are exported to markets including Japan, Singapore, Hong Kong, and Malaysia.

Su Jiayi has produced a snack combining sweet potatoes and Yunlin peanuts; has used red beans from Wandan Township in Pingtung County as a filling to produce red-bean sweet potato balls; and has developed a sweet potato croquette. He has also created a sweet potato and yam red-bean soup to beat summer heat as well as a sweet potato and yam chicken soup intended as a winter tonic food, both of which have proved popular in Hong Kong. Japanese consumers, on the other hand, prefer deep-fried sweet potato chips, while frozen sweet potatoes are sold to the ethnic Chinese market in the US.

Su Jiayi notes the development of sweet potatoes from a sweet treat to a main course dish, saying, “We use this high-quality Taiwanese agriproduct with nothing added, bringing out the original flavor to create ‘stylish sweet ­potatoes.’”

Chiu Mu-cheng, founder of K.K. Orchard in Tainan’s Xinhua District, started off with wholesale and retail sales of sweet potatoes. The opening of McDonald’s franchises in Taiwan in the 1980s set off a fad for French fries, and this inspired Chiu to cut visually unattractive sweet ­potatoes into fries and crush them into paste to make sweet potato tots, both of which he sold through the TKK Fried Chicken and Chicken House chains. Later he founded his own processing plant and is now the supplier of sweet potatoes for baking to FamilyMart convenience stores. To maintain consistent quality, K.K. Orchard has long been contracting farmers to grow the potatoes. The company also exports frozen pre-cooked sweet potatoes for baking, and sweet potato chips. This year they signed a memorandum of understanding with a Japanese business to sell sweet potato products in Okinawa.

Ching Chiuan Technological Agriculture Company, a Changhua-based specialist wholesaler of fresh sweet potatoes, is working with CAEB to lengthen the storage life of produce in the supply chain. “We are continuously working on bud inhibition and freshness preservation technologies in order to support farmers,” says Yi-tan Denise Fang, the director of CAEB.

Sweet potato farmers in Yunlin’s Shuilin Township have integrated their entire production process, and are exporting their sweet potato products overseas. (courtesy of Uncle Sweet)

Sweet potatoes have left behind their reputation as a cheap, low-grade food and are now seen as a national food linked to history and culture.

Su Jiayi has developed filled sweet potato balls that are proving popular in both domestic and foreign markets. (courtesy of Uncle Sweet)

Team sweet potato

Three years ago, Chiu Mu-cheng brought together sweet potato farmers and related companies to establish the Taiwan Sweet Potato Industry Development Association. The group shares experience with cultivation, technology and marketing, and promotes overseas sales.

This spring, K.K. Orchard and CAEB put on a well-­attended field demonstration of automated farm equipment including plastic mulch layers, planters, and harvesters, machines imported through a public–­private partnership. “In the past, ten people could harvest 6,000 square meters of sweet potatoes in eight hours, but with mechanization three people can harvest 8,000 square meters, doubling the efficiency,” says Huang Che-lun, an associate researcher at CAEB.

This public–private partnership can address the labor shortage in the agricultural sector. Denise Fang says that the streamlining and mechanization of the sweet potato value chain will help upgrade the industry, and that in the future AI will be introduced into agricultural equipment to make it easier for farmers to operate.

“Nowadays you can buy sweet potatoes in the cooked food sections that are prominently located in convenience stores. This is remarkable,” says Tsai Cheng-hao.

Over 400 years, the little sweet potato has become part and parcel of Taiwan’s terroir and popular culture, and today farmers are determined to create new value for this once neglected food.

Try a Taiwan sweet potato, savor its fragrant sweetness, and your soul will soak up the innovativeness and values of Taiwan.

The Ministry of Agriculture is working with farmers to introduce sweet potato harvesters into Taiwan, to help reduce farmers’ workload. (photo by Mei Kuo)

The sweet potato, an introduced vegetable that has set down deep roots in Taiwan, is also a symbol of the island’s values and spirit. (courtesy of K.K. Orchard)