Jump to main content
Reading the Leaves: Tea Identification by Soil Nutrient Analysis
2023-07-31

Tea Research and Extension Station (TRES) deputy director Chiu Chui-feng says that Taiwan has tea plantations in areas from the plains to the high mountains, and produces a variety of unique teas based on their different environments and microclimates.

Tea Research and Extension Station (TRES) deputy director Chiu Chui-feng says that Taiwan has tea plantations in areas from the plains to the high mountains, and produces a variety of unique teas based on their different environments and microclimates.
 

Every tea leaf grown in Taiwan is affected by its local terroir, and each sip of tea reveals the tea maker’s craftsmanship..

Exports of oolong tea from Taiwan began 150 years ago, and its unique flavor established an excellent reputation for Taiwanese tea. Today, Taiwanese teas are developing in the direction of specialty teas, with many tea-growing localities building on their own distinctive characteristics, and tea has become a popular gift purchase for international tourists visiting the island.

When you buy Taiwanese tea these days, you can tell where it was grown based on its geographical certification mark and its food traceability QR Code. In addition, the Council of Agriculture’s Tea Research and Extension Station (TRES) has developed a testing protocol based on analysis of soil nutrients to determine where tea leaves were grown, to ensure that fans of Taiwanese tea can enjoy the authentic taste of Taiwan.

 

The flavor and mouthfeel of tea depends on the cultivar used, the tea plantation’s field management, and the craftsmanship of the tea processor; every link in the chain matters.

The flavor and mouthfeel of tea depends on the cultivar used, the tea plantation’s field management, and the craftsmanship of the tea processor; every link in the chain matters.
 

A history of Taiwanese tea

Looking at the history of the tea industry in Taiwan, we find that there are records of tea plants being introduced into Taiwan as early as the era of Dutch rule in the 17th century. In 1869, the Scottish merchant John Dodd and the Dadaocheng-based businessman Li Chunsheng exported “Formosa Oolong Tea” to New York, and its unique, delicious flavor established Taiwanese oolong tea’s high status. During the era of Japanese colonial rule (1895–1945), tea was Taiwan’s leading export product.

In the 1980s, as international trade flourished, some Taiwanese tea growers relocated their tea plant cultivars, tea-making technology, and expert manpower overseas to countries with lower production costs, and since then tea grown in Taiwan has mainly supplied the domestic market. However, Su Tang-chao, deputy director of the Crop Production Division of the Agriculture and Food Agency under the Council of Agriculture, says that the techniques and technologies used in Taiwan for cultivating and processing tea have become even more refined in response to the specific environments and climatic conditions of different localities, and diverse specialty teas have been developed as a result.

TRES deputy director Chiu Chui-feng notes that tea plants thrive in warm, humid environments, and need to be grown in acidic soil. In Taiwan, tea is mainly cultivated in low-elevation hill country, on mountain slopes, and in high mountain areas, at elevations ranging from ten to 2,650 meters above sea level. The lower temperatures at higher elevations reduce the catechins in the freshly picked tea leaves, which minimizes any bitter and astringent taste in the tea brewed from the leaves, and enhances the fragrance. This makes Taiwanese tea smoother to drink. Moreover, the tea from each different locality has its own special character and charm.

An age of refinement of domestic tea

Chiu elaborates on the types of specialty teas that Taiwan produces, which broadly fall into eight categories: ­unfermented Bi-Lo-Chung (biluochun) green teas; Wenshan Pao­chong (baozhong) teas, with various degrees of fermentation; High-Mountain Oolong (wulong) teas; Tongding (dongding) Oolong teas; Tieh-Kuan-Yin (tieguanyin) teas; Oriental Beauty (dongfang meiren) teas; Red Oolong teas (a.k.a. Black Oolong); and fully fermented black teas.

“Of the world’s ten leading tea-producing countries, virtually every one produces only a single type of tea. For example, India and Sri Lanka produce black teas while Japan makes green teas. There is no other place like Taiwan, a small island which can produce green tea, high-mountain tea, oolong tea, and black tea. This is because Taiwan has a wide variety of environments and microclimates, creating diversity and special characteristics in different tea-growing areas,” says Chiu.
 

Tea plants absorb nutrients from the soil. After the leaves are picked, processed, and brewed, you can taste the flavor of the unique terroir in the tea in your cup.

Tea plants absorb nutrients from the soil. After the leaves are picked, processed, and brewed, you can taste the flavor of the unique terroir in the tea in your cup.
 

Upgrading to specialty teas

Taiwan oolong tea made its worldwide debut 150 years ago. But what exactly is Taiwan oolong tea?

Chiu says that based on the degree of fermentation and roasting, Taiwan’s oolong teas can be divided into two types: fragrant oolongs, and heavily roasted oolongs.

Fragrant oolong tea is best represented by high-­mountain oolongs. In terms of appearance, the leaves are tightly wound into balls, while the tea liquor is clear, bright, and glossy. The fragrance originates in the tea leaves themselves, which have a pure, slightly floral aroma, while the liquor has a delicate aftertaste. This type of tea was developed relatively recently and requires the most meticulous processing techniques. It is the most difficult type of tea to manufacture.

Roasted oolongs include Tongding oolong, Tieh-Kuan-Yin, and red oolong. As the name suggests, they all have a roasted fragrance, with a rich aroma and mellow taste. Red oolong is a newly emerging specialty tea that is suited to both hot and cold brewing.

In recent decades the Council of Agriculture has held a number of tea manufacturing competitions to promote a culture of expertise and professionalism in the tea industry, while tea farmers and tea companies have endeavored to promote Taiwanese teas to the world and enhance the reputation of the “Taiwan tea” brand. In addition, the Nantou County Government has registered the production processes for the Tongding oolong tea grown in Lugu Township and the tea grown at Puzhong in Mingjian Township as intangible cultural heritage, and Su Wenzhao and Chen Mao­chun, two local masters of traditional manual methods of tea processing, have been recognized as “cultural heritage conservators.” Such measures are facilitating the transmission of tea manufacturing craftsmanship and culture.

Identifying tea leaves’ origin

“Taiwan has long had a reputation for high-quality tea,” says Su Tang-chao. To ensure that consumers can be confident that the tea they drink was grown and processed in Taiwan, more than a decade ago TRES began developing a test method for detecting multiple chemical elements in tea leaves, to identify nutrients absorbed from the soil. They grind the leaves into a powder from which they extract a solution, then use inductively coupled plasma mass spectrometry (ICP-MS) to analyze the presence and concentrations of 14 trace elements including lithium, vanadium, chromium, copper, and zinc. Finally they compare these results with a database of tea leaf trace elements compiled from tea samples collected from around the world, to determine the country where the tea was produced.

Chiu Chui-feng says that tea is a drink consumed for pleasure, and people in different countries have different preferences depending on local dietary culture. Because Taiwan is famous for oolong tea and it is consumed in large amounts, the first teas tested for their place of origin using ICP-MS were oolongs (high-­mountain Tongding) made from the widely grown Chin-Shin Oolong and TTES No. 12 (Jhinhsuan) cultivars. The tea database assembled by TRES currently includes more than 700 varieties and the accuracy rate for determining place of origin is around 98%.

Jason T.C. Tzen, a professor in the Graduate Institute of Biotechnology at National Chung Hsing University (NCHU), says that the cultivars used for imported and domestic oolong teas are the same, meaning that the tea plants have identical DNA, so that this is not a useful basis for distinguishing domestic from foreign teas. That is why TRES uses soil trace elements in the tea leaves to determine the place of origin.

Professor Lai Chien-chen of NCHU’s Institute of Molecular Biology explains that plants derive most of their nutrients from the soil, so that there is a correlation between the small or trace amounts of important chemical elements in plants and the composition of the soil where they grow. Because soils differ around the world, with each location having its own profile of trace element concentrations, the place of production can be determined by measuring the trace elements in the plant tissue.
 

TRES has brought innovation and creativity into play to develop a new generation of tea drinks.

TRES has brought innovation and creativity into play to develop a new generation of tea drinks.
 

Geographic certification

Another way to determine whether tea was cultivated in Taiwan is the geographic certification mark. Su Tang-chao explains that tea vendors can only label their tea with such marks after receiving third-party certification.

The criteria for certification include safe use of pesticides, field management, and food safety and hygiene management. The teas must also pass sensory evaluations of their taste, fragrance, and color, and the appearance of the brewed leaves. In these ways quality control is ­ensured.

To date, geographic certification marks have been registered for teas produced in 15 localities, including Lugu (for Tongding oolong tea), Alishan (for high-mountain tea), and Lishan.

On January 1, 2023, the Agriculture and Food Agency began implementing a mandatory traceability mechanism for domestically produced tea. For all unbrewed tea leaves, if the label indicates Taiwan as the sole country of origin, then the packaging must also show a domestic tea traceability QR Code, a Traceable Agricultural Products label, or a certified Taiwan organic produce mark. If the product is a mixture of domestic and foreign teas, the label must list the countries of origin in order of the relative proportions of tea from each country. Su says that the goal behind the government’s efforts to promote place of origin labeling through technology, legislation, and policy implementation is to protect the rights and interests of the buying public.

Each little rolled-up tea leaf carries within it the verdant greenery of the tea plantations, and the charm and terroir of the particular mountain area where it was grown. Moreover, it embodies the locally embedded craftsmanship and innovative spirit of the people whose skills create that elegant fragrance and sweet, mild after­taste. Come to Taiwan and take the opportunity to experience the pleasures of Taiwan tea for yourself!

For more pictures, please click 《Reading the Leaves: Tea Identification by Soil Nutrient Analysis