The Science Behind Dancong Oolong Tea Taste and Aroma

Posted by Boyka Mihaylova on

"Champagne of teas", "the perfume of teas" are just a few among the nicknames of one of the most beloved teas out there, namely Dancong Oolong tea. Although Oolong tea came out as the last addition to the millennia-long tea history of China, it quickly gained popularity. It established itself, stealing the crown of red tea, or Hong Cha, as the most aromatic tea among the six tea types.

In this blog post, we'll unveil the mystery behind one of the most captivating aromas in the world of tea. We'll explore the factors that influence the formation of Oolong tea taste and aroma, and analyze the factors behind it, both from nature and science's points of view. We're talking specifically about Dancong Oolong, as it's the one type of Oolong tea with the most abundant variety of aroma profiles. However, the factors that influence the formation of the aroma and taste of Dancong Oolong apply to virtually any type of loose leaf oolong tea. Ready for it? Let's begin! 


The chemistry behind Oolong tea taste and aroma

Before elaborating on Oolong tea taste and aroma, let's first mention that different factors can influence the formation of tea taste and smell in any type of tea; some of them are naturally present in the tea plant, some of them form throughout the process of turning fresh tea leaves to finished tea, and others are external factors of the tea plant's growing environment. We'll get into the details of each group shortly, but before that, let's make a quick chemical overview.

The proportion of aromatic substances in fresh tea leaves is indeed tiny. Only 0.005% to 0.03% of the inner compounds of tea leaves are aromatic substances, yet there are over 80 types of them. They are a crucial factor affecting the quality of tea. Regarding the amount of aroma substances present in the finished tea, the six tea types are not created equal. For example, there are over 260 types of aromatic substances found in green tea. Black tea (hong cha) has over 400 types, while Dancong Oolong tea has whooping 500 types.


So far, over 700 tea aroma compounds exist naturally or form throughout the process of turning fresh tea into a finished tea.


According to a color spectral analysis, the most important types of aromatic substances in tea include alcohols, aldehydes, ketones, esters, lactones, phenols and their derivatives, sulfur and nitrogen-containing compounds.


A matter of taste

Dancong Oolong tea is known for its distinct fragrance and flavor. It comes in a wide variety of aromas, captivating tea enthusiasts both locally and internationally. The Dancong Oolong tea taste and especially aroma are so intense and pervasive that some tea lovers question whether they are natural or artificially enhanced.

Truth is, several factors, both internal and external, impact the formation of the Dancong Oolong tea taste and aroma. First, there's the inherent scent of the tea leaves themselves. Then, there's the influence of the tea tree's surrounding environment – the soil, climate, and overall ecology where it grows. The third component is the aroma developed through the tea's production and roasting process. Lastly, aged Oolong teas develop a unique, mature fragrance over time. Each element combines to create the signature aroma of Dancong Oolong tea, making each sip a delightful experience.


loose leaf oolong tea


The Root of Aroma: Tea Leaf's Natural Scent

Let's start with the aroma that is already present in the tea leaves. In their fresh state, tea leaves already contain a plethora of scents nestled inside the plants' cells, including aromatic compounds like linalool and dihydro linalool, to name a few. The specific mix and concentration of these elements shape the distinct Oolong tea taste and aroma profile. Some of the fresh and floral notes we sense in tea have already been programmed by the very presence of these substances inside the tea leaf; however, to get the Oolong tea taste and aroma to develop to their fullest potential, the tea needs to go through some processing – which takes us to the next impacting factor.


From Leaf to Fragrance: The Art of Processing Oolong Tea

While the leaf naturally contains a certain amount of aromatic substances, they alone in their latent state wouldn't be enough to produce the intensive, almost intoxicating Dancong Wulong aroma we know so well. It is largely formed within the production process. The drying and cooling of the leaves starts the process of release of the fragrance compounds. The real action, however, happens in the "making of the green," or "zuo qing" (做青), where the tea master would toss, turn, and rest the leaves. Stimulated by the friction and heat, the aromatic substances break loose from the torn cell walls of the tea plant. That, in turn, triggers a reaction of oxidation, where certain enzymes mingle with tea polyphenols and transform them, further enriching the Oolong tea taste and aroma. This transformation during the tea processing, especially during the enzymatic oxidation and final drying stages, crafts the unique aromatic signature of Dancong tea varieties.


The making of Oolong tea is a delicate process that greatly influences its aroma. 


Withering, especially at low temperatures, is crucial for developing a subtle fragrance. Oxidation further shapes the tea's color, aroma, and taste. If the oxidation is not enough, the tea may taste bitter and retain an overly "grassy" flavor; too much of it and the aroma weakens. The next step, "killing green", halts oxidation by using heat to stop enzyme activity, evaporate moisture, and enhance the tea's floral scent, preparing it for rolling. Rolling compresses the leaves, releasing their juices and making the tea endurable to brewing. Finally, drying stops the oxidation entirely and brings out additional notes in the Oolong tea taste and aroma. The temperature must be just right: too high, and you lose aromatic compounds; too low, and the enzymes aren't fully stopped, muddling the tea's scent. Roasting is the last touch, where sugars and amino acids transform, adding caramel-like notes. Using charcoal in roasting, a traditional technique, intensifies this effect. The charcoal's heat expels any "grassiness" and adds a smoked touch to the flavor profile to craft a tea brew with a distinct charm and superior quality.


dancong oolong


Terroir's Touch: Climate and Soil in Oolong Tea Taste and Aroma

The environment also plays a defining role in shaping Oolong tea's taste and aroma. Things like soil composition, rainfall, exposure, altitude, and tree age all leave their mark on each tea's unique flavor profile.

Let's take Dancong as an example. The yellow soil that prevails in the region of Chaozhou is rich in organic matter and dozens of minerals and trace elements. The tea plant absorbs them and transfers their metabolites to the buds and leaves, creating a rich and layered flavor profile. In turn, dark red soil and paddy soil, with their excellent moisture and warmth retention, are slightly acidic with a pH of 5.5-6.5. That makes them ideal for tea tree cultivation. These soils are common in lower mountainous regions and areas where fields have been converted to tea plantations. Their characteristics contribute to the robust growth of tea trees, ensuring a rich harvest of quality leaves.

The tea tree age is directly related to the soil and how the plant interacts with it. Young tea trees have more shallow roots. That makes them susceptible to changes in rainfall, sunlight, and temperature. They can't reach into the deeper layers of the soil. That often results in a lighter, fainter brew that doesn't hold up well against multiple steepings. However, as tea trees mature, their roots extend deeper and spread out, becoming resilient to environmental stresses like drought or extreme temperatures. This stability ensures a consistent growth of new shoots. Mature tea trees draw up deep-seated nutrients, giving their leaves a distinctive taste. The tea made from these mature leaves is richly aromatic, with a lingering sweetness in every cup.

Altitude also has a say in the overall flavor profile of Oolong tea. Aside from the specific soil composition in the higher parts of the tea mountains, other specifics like day/night temperature variations, increased UV radiation, and the year-round presence of clouds/ fog influence the growth and metabolism cycle of the tea tree, altering the leaves' composition and ultimately creating the unique "mountain flavor" or "rock flavor"- a signature mark of a high-quality Oolong.


Aged to Perfection: The Impact of Storage on Oolong Aroma

We're used to associating aging and storage mostly with Dark Tea (Hei Cha) and the ubiquitous Pu-erh tea. You might be surprised to learn that in Fujian, Taiwan, and Chaozhou, among others, people have long cherished the tradition of aging Oolong tea. Properly stored aged Oolong tea undergoes a natural transformation over the years. With proper storage, the polyphenols inside the tea leaves transform, creating unique flavor profiles and a distinctive mouthfeel that sets it apart from Pu'er and dark teas. With expert processing, thorough and repeated charcoal roasting, along with proper storage conditions, Oolong tea's aroma deepens over time. The initial surface notes give way to a richer bouquet, yielding a tea soup that gains complexity with age. As the years pass, the color of the tea darkens to a bright, clear red, and the taste becomes increasingly smooth.