Delivering Quality Tea - 140000 + Customers

Brew cafe logo
Differences between black tea and oolong tea

Differences Between Black Tea and Oolong Tea

Did you know over 3 billion cups consumed daily? But not all teas are created equal – subtle differences in processing result in distinct taste profiles, caffeine levels, and health benefits. Nowhere is this more apparent than when comparing two beloved types: fully oxidized black tea and semi-oxidized oolong tea. Though originating from the same Camellia sinensis plant, the nuances in production yield dramatically different brews brimming with unique flavours, appearances and cultural significance. In this post, I will show you some common differences you can find between Brew Cafe’s Assam Black Tea and Darjeeling Oolong Tea.

What is Black Tea?

Black tea is one of the most widely consumed teas globally. Black tea is made from leaves that have been fully oxidized, resulting in its signature dark black leaves. Popular black teas include Assam, Ceylon, Darjeeling, Keemun, and Lapsang Souchong.

Assam Black Tea

The leaves for black tea are first picked, then withered to remove moisture, rolled to release juices, and finally exposed to oxygen which causes full oxidation. This oxidation results in the distinctive dark coloured leaves. The leaves are then dried to finish the tea production process.

Benefits of Black Tea

  • High in antioxidants like flavonoids
  • Contains caffeine for an energizing boost
  • May support heart health by reducing LDL cholesterol and blood pressure
  • Black tea polyphenols may protect cells from damage
  • May benefit gut and oral health

What is Oolong Tea?

Oolong tea originates from China and is sometimes referred to as the “black dragon tea.” It can range from green to dark brown in colour. The defining characteristic of oolong tea is that the leaves are only partiallyoxidized during processing. This results in oolong’s smooth, fragrant taste that falls between non-oxidized green tea and fully oxidized black tea.

Oolong Tea Health

Popular varieties of oolong include Da Hong Pao, Dan Cong, Ali Shan, and Ti Kuan Yin. The three main types are Chinese, Taiwanese, and Vietnamese oolong.

Benefits of Oolong Tea

  • High in antioxidants and polyphenols
  • May boost metabolism and aid weight loss
  • Linked to lower risk of type 2 diabetes
  • Oolong tea polyphenols may reduce inflammation
  • May improve heart and brain health

Common Differences between Black Tea and Oolong Tea

There are several key differences that set apart the two tea types, from the oxidation process to caffeine content and more.


Oxidation is one of the most crucial steps in processing different styles of tea. This process exposes the tea leaves to oxygen, which causes chemical changes that result in new Flavors and aromas. The level of oxidation is what distinguishes black teas from oolongs.

Brew cafe Assam CTC
Brew Cafe Assam CTC

Assam Black tea goes through full oxidation, ranging from 90-100% depending on the tea maker.

Darjeeling oolong tea only undergoes partial oxidation, typically between 20-80%. Partially oxidized teas like oolong have lower levels of theaflavins and thearubigins compared to fully oxidized black tea. For example, one study found an oolong tea to have only 1.9 mg/g of theaflavins versus 11.9 mg/g in a black tea sample.

Brew Cafe Oolong CTC
Brew cafe Oolong CTC

The oxidation percentages and compounds present are summarized below:

Tea TypeOxidation LevelTheaflavinsThearubigins
Brew Cafe Assam Black tea90-100%HigherHigher
Brew Cafe Darjeeling Oolong tea20-80%LowerLower

This wide range of oxidation is why oolong teas can take on fruity, floral or more roasted characteristics while black tea has its trademark bold, malty taste.

Flavour Profile:

The distinct flavour profiles of black tea and oolong tea come down to their differing chemical compositions. The key compounds influencing the taste are polyphenols, amino acids, and volatiles.

For example, one analysis found black tea has approximately three times more polyphenols than oolong tea.

Black tea contains higher levels of theaflavins and thearubigins from full oxidation, contributing to its robust, brisk character. Oolong teas tend to have more catechins like EGCG that lend a smooth, sweet roundness.

Black tea also has more gallic acid, contributing to pronounced bitterness compared to oolong’s mellow profile. The amino acid composition affects the mouthfeel and aftertaste.

Here is a comparison:

Tea TypeKey Flavour CompoundsTaste Profile
Brew Cafe Assam Black teaHigher in theaflavins, thearubigins, gallic acidBrisk, bold, malty
Brew Cafe Darjeeling Oolong teaHigher in EGCG, other catechinsSmooth, floral, sweet

Oolong teas can take on fruity and honey-like notes thanks to volatile compounds formed during careful processing. These nuances give oolong tea its layered depth versus black tea’s straightforward robustness.

Processing Method

The sequence of steps in processing determines whether tea leaves end up as black tea or oolong tea. Both go through withering and drying, but the key differences are in rolling, oxidizing and fixing.

Tea leaves

Black tea is more heavily rolled to bruise the leaves and accelerate oxidation. The leaves are then fully oxidized for up to 4 hours during which the catechins transform into theaflavins and thearubigins. Oolong tea is more gently rolled or shaken and then undergoes shorter partial oxidation for just 2-3 hours.

Oolng leaves

Oolong teas are often rolled into balls or twisted shapes. The oxidation is stopped at a precise moment by “fixing” through heating. Black teas do not undergo fixation since full oxidation is desirable.

The processing time results in the following:

Tea TypeWitheringRollingOxidationDrying
Brew Cafe Assam Black tea12-18 hrsHeavy2-4 hrsFires or warm air
Brew Cafe Darjeeling Oolong tea2-3 hrsGentle20-80%Over charcoal

It is remarkable how the subtle differences in production yield such contrasting teas from the same plant. Both methods unlock unique flavours and characters from the tea leaves.


The visual differences between black tea and oolong tea start with the dry leaves and continue into the brewed beverage.

Brew cafe Assam black tea: A steaming cup of rich and aromatic black tea from Assam

Dry black tea leaves are very dark brown, black, or deep red as chlorophyll breaks down due to full oxidation. Oolong’s partial oxidation results in dry leaves that are dark or light green depending on the specific level of oxidation.

A steaming mug of Oolong tea, brewed to perfection

When brewed, black tea ranges from rich reddish-brown to dark brown with orange undertones. The higher levels of theaflavins and thearubigins lead to the deep, opaque brew. Oolong tea has a light gold, amber, or coppery brew in the cup. The lower oxidation leaves clarity and a brighter tone.

Here’s a comparison:

Tea TypeDry Leaf ColourBrewed Colour
Brew Cafe Assam Black teaBlack/dark redReddish dark brown
Brew Cafe Darjeeling Oolong teaGreen to brownGold/light brown

The dramatic colour differences are a beautiful visual showcase of what happens to tea leaves during delicate processing steps like oxidation. Both brews have an appealing elegance.

Health Benefits

Both black tea and oolong tea contain various bioactive compounds that may promote health, but some of their benefits differ.

For example, black tea contains 25-48 mg caffeine per 8 oz cup according to one study, providing more of a caffeinated energy boost than the approximately 37 mg in the same serving of oolong.

However, oolong has higher levels of catechins that are linked to weight loss benefits. One analysis found participants burning an extra 281 calories per day drinking oolong compared to water.

Oolong tea in a clear glass teapot with steam rising, showcasing its rich amber color and delicate aroma
Oolong tea in a clear glass teapot with steam rising, showcasing its rich amber color and delicate aroma.

Oolong also shows advantages for heart health, with one study finding daily oolong drinkers showing a 61% lower risk of cardiovascular disease mortality.

Here is a summary:

Tea TypeBenefitsKey Bioactive Compounds
Brew Cafe Assam Black teaAlertness from caffeineCaffeine, theaflavins
Brew Cafe Darjeeling Oolong teaWeight loss, heart healthCatechins like EGCG

Both teas can be part of a healthy lifestyle. The choice comes down to your specific health goals.

Cultural Significance

Both black tea and oolong tea are deeply ingrained in the cultures where they originated.

For instance, black tea plays a central role in the United Kingdom’s cultural identity. The British consume 60.2 billion cups of tea annually, with black tea blends like English Breakfast Tea being trendy. Afternoon tea is a beloved ritual, and black tea appears in classic British novels, movies and art.

Meanwhile, oolong tea is revered in Chinese culture. The Chinese drink around 700,000 tons of oolong tea every year. Complex Chinese tea ceremonies have developed around oolong tea, with specific steps to brew and appreciate it. Roasted oolong is savoured during the autumn Qixi Festival. And the art of Chinese gongfu tea incorporates exceptional oolongs.

Here is a comparison:

Tea TypeCultural SignificanceUnique Traditions
Brew Cafe Assam Black teaEnglish and Irish cultureAfternoon tea, tea and scones
Brew Cafe Darjeeling Oolong teaChinese cultureTea ceremonies, gongfu tea

Both teas have become icons through the practices, rituals, and media of their native cultures.


While black tea and oolong tea come from the same plant, they have distinct characteristics from their taste and appearance to their caffeine content and health benefits. Black tea offers a bold, brisk flavour and energizing lift while oolong provides a smooth, floral and fragrant experience. Tea lovers may enjoy incorporating both types into their daily routine to receive the unique advantages of each amazing tea.

Leave a Comment

Your email address will not be published. Required fields are marked *

Shopping Cart