Is a Semi-fermented Tea an Oolong?

difference in health chemistry

In a study done in Kenya (1), where tea plantation was introduced in the 1920s by the British for black tea to satisfy the colonists’ home empire, scientists found that the amount catechins decreases as do theaflavins, the major health flavonoids in black tea, as the temperature during fermentation increases from 20°C to 30°C. As mentioned earlier, temperature is raised for black tea fermentation to hasten the process, most of the time higher than 30 in major commercial productions.

Data from “Changes in the chemical and sensory quality parameters of black tea due to variations of fermentation time and temperature”.
Units:
For theaflavins: millimoles/g tealeaves,
for sensory: basing on a 1~11 ranking by professional tasters. This chart is much simplified for easy reading, all data based on the means obtained from the report. For more details, pls refer to the report.

The slow process with which oolong is fermented produces a material nature quite unique which scientists have yet to define. Oolongs have found to be a most potent tea in cancer prevention and other anti-mutagenic, anti-oxidative activities (2). It is reportedly more potent than green tea in reducing fat accumulation in the body (3). It appears that a critical amount of residual green tea catechins works in synergy with the more potent forms and abundant amount of gallic acids and tea saponins in oolong contributes to the benefits (4). This is unique in oolong.

difference in taste

Health benefits aside, oolongs generally taste brighter and livelier. Premium oolongs are always sun withered and shade rested without being piled up before the time consuming fermentation process. <click here to read more about traditional fine oolong production> On the other hand, in the same study done in Kenya, scientists concluded that prolonged heat exposure during fermentation results in teas tasting only half as bright as that in room temperature. Oolongs are fermented in room temperature and most black teas not.

Semi-fermenting tea is not restricted to black tea production. This is a semi-black white tea, encompassing the wonders of white tea in a more familiar “black” kind of taste.

The greatest difference, however, maybe the great diversity of cultivars and production styles developed over hundreds of years entirely dedicated to oolong production. Where a black tea plantation maybe covered with three to four cultivars, some only one, traditional oolong regions strive with a huge range. They yield leaves of different appearances and different chemistry for different taste characters. Variations in processing possible only by highly skilled and experienced tea masters in the tradition of their regions offer a huge range of varieties incomparable by simply adapting a mechanized black tea procedure.

semi-fermented black teas and oolongs are two types of teas

That is why there are farmers from black tea regions experimenting specialized oolong cultivars and learning the production skills to try producing real oolongs. They know they have to be genuine in order to take a sustainable share of the market.

It is the experience in drinking the tea that really counts, after all. Indeed, all professional tasters I know who have had the experience with a wide quality range of half-fermented black tea and oolongs would agree that they are two different groups of teas.

The next time you shop, read the label for clues. Compare notes with the different articles here in this site. Compare your sources and you may soon discover a whole different level of enjoyment.

Answers to the question in page 1: from left to right: Classic oolong Wuyi Rougui, a Himalayan half-fermented black tea, a Himalayan black tea, and a Vietnam made Taiwan style oolong

footnotes

1. M Obanda et al, Changes in the chemical and sensory quality parameters of black tea due to variations of fermentation time and temperature, Food Chemistry 75 (2001) 395–404

2. JJ Dong et al, Inhibition of angiotensin converting enzyme (ACE) activity by polyphenols from tea (Camellia sinensis) and links to processing method, Food & Function, 2011, 2, 310, and

YS Lin et al, Factors Affecting the Levels of Tea Polyphenols and Caffeine in Tea Leaves, Journal of Agricultural and Food Chemistry, 2003, 51, 1864−1873

3. Y Kimura et al, Anti-obesity effects in rodents of dietary tea saponin, a lipase inhibitor, International Journal of Obesity (2001) 25, 1459 – 1464

4. V Lee et al, Massive Accumulation of Gallic Acid and Unique Occurrence of Myricetin, Quercetin, and Kaempferol in Preparing Old Oolong Tea, Journal of Agricultural and Food Chemistry, 2008, 56, 7950–7956, and same sources as in footnote 2