Tea comes in such a wide variety of tastes, aromas, and flavours–from sweet and vegetal, to fruity and floral. This amazing variety all comes from a single plant: Camellia Sinensis. Through various methods of breeding, cultivation, and processing, all of the different flavours of tea can be produced. While the processes that create these flavours are incredibly interesting in their own right, they are rather complicated and deserve their own post (such as our deep dives into shading and its effects on taste). Here, we will focus on the basics: what is ‘flavour’ and what chemicals give teas their various tastes and flavours.

The Difference Between Taste, Aroma, and Flavour

Before we dive in, it is important to note the difference between ‘taste’ and ‘flavour’. Both on our website and elsewhere, these two words are used more or less interchangeably, but strictly speaking, they are not the same. 

Taste

Taste, unsurprisingly, refers to sensations experienced in the mouth through your taste buds. There are only five basic tastes: sweet, sour, salty, bitter, and umami. Each occurs when various receptors detect the presence of various chemicals. For example, you taste sweetness when you detect sugars, sourness when you detect acids. While you are certainly familiar with the first four of these tastes, umami may be unfamiliar. 

Umami (旨味) is the taste associated with protein or amino acid rich foods, such as meats, fish, mushrooms, etc. For some people, it is easier to associate umami with liquid foods, such as soy sauce or miso soup. Umami plays a key role in Japanese cuisine, where it was first isolated as a basic taste in 1908. In tea, umami is mostly present in green teas, especially Japanese green teas, where it is sometimes identified as a ‘brothy’ taste.  The term ‘savoury’ is sometimes provided as a translation, however this often conjures up the wrong idea, with an association with the salty, fatty, or smokey tastes of meats or cheeses. For reasons of precision, the term ‘umami’ is often preferred over ‘savoury’. 

In addition to the five basic tastes, there are various other oral sensations, such as spiciness and numbness. The two additional sensations most applicable to tea are astringency and kokumi (Kokumi (こく味) or just koku refers to ‘fullness’ or ‘body’ in taste). These are much more complex and deserve their own blog post.　

Aroma

Aroma (or in less fancy lingo: smell) occurs in the nose, when volatile molecules, also called aromatic compounds, are released by the tea and are either breathed in through the nose or travel from the mouth to the nose in a process called retronasal olfaction or retro-olfaction for short. In either process, the brain groups the dominant smells together as distinct ‘odour objects’. These can either be made of a singular chemical or a combination. The odour objects that your brain creates depend on your genetics and experiences.

For example, a Japanese person may associate the smell of coumarin in a sencha with the aroma of sakura mochi, whereas an American person might smell vanilla or cinnamon. It is worth noting that the brain can only process about three or four odour objects at once, so don’t be dismayed if you can’t think of more than three tasting notes for a tea.

Flavour

When we combine taste and the aroma sensed through retro-olfaction, we get flavour. In other words, flavour cannot exist without aroma. This is why your sense of taste (or rather flavour) is dulled when you are sick or have nasal congestion.

The Taste of Tea

When it comes to tea, bitterness, sweetness, and umami are the primary tastes, with salty and sour tastes rarely encountered. Generally speaking, people enjoy sweetness and umami, and dislike bitterness, or at least excessive bitterness. This simple fact shapes how we grow, process, grade, brew, and enjoy tea.

Bitterness in Tea

The primary bitter-tasting compounds in tea are catechins: a group of chemicals that the plant uses to protect itself from sunburn and fungal growth. Catechins are also the main form of antioxidants found in green tea, most commonly in the forms of epicatechin (EC) and epigallocatechin (ECGC). Despite being good for your health, they are some of the bitterest compounds in tea. When tea leaves are oxidised, say to produce black tea, these simple catechins link together to form larger polyphenols, also called tannins, which give black teas their distinctive taste, astringency, and reddish colour. This means that catechins exist in the highest concentrations in green teas.

As far as Japanese green teas go, catechins make up around 11-17% of the processed leaves' water soluble components. For sencha, this number is typically around 15-17%, whereas it is lower, around 11-12% in shaded teas like gyokuro, which is one reason why gyokuro is less bitter than sencha. 

Another bitter-tasting compound is caffeine. Though not as bitter or as prevalent in tea leaves as catechins, caffeine bonds with at least 6 different bitter-detecting receptors on the tongue. However, its perceived bitterness varies from person to person due to a genetic mutation. This mutation is found in over 90% of people of East Asian descent, 75% of those of European descent, and 10-30% of those of African descent.

Umami in Tea

The centrepoint and defining characteristic of most Japanese green teas, umami is the rich, pleasant, brothiness or savouriness that is found in abundance in matcha and gyokuro (due to shading), but is still very much present in sencha and other green teas. 

Umami comes from amino acids, which are the building blocks of proteins. Theanine or L-theanine is by far the most abundant amino acid in tea making up over half of the total amino acids (and is in fact named after tea, when it was first isolated from gyokuro leaves). Theanine has a sweet and umami taste and when consumed with caffeine (as in tea) it seems to act together with caffeine to produce a calming, focusing effect on the mind.

Additionally, theanine is largely responsible for the aforementioned sensation of kokumi, or that rich, full-bodied mouthfeel of some teas.

The other amino acids found in tea are Glutamic acid, Aspartic acid, and Arginine. 

Amino acids typically make up around 2-3% of sencha and 4-5% of gyokuro and matcha. However, some extremely high-grade teas can have amino acid levels over 10%! 

Sweetness in Tea

Of course, sweetness comes from sugars, such as sucrose, fructose, and glucose, all three of which are found in tea, as the products of photosynthesis. 
However, amino acids can also bond to sweetness receptors, meaning that high-umami teas also taste sweeter.

There is another particular type of sweetness associated with tea: the sweet aftertaste. Called hui gan (回甘 - returning sweetness) in Chinese and yoin (余韻 - afterglow) in Japanese, this effect can be produced by a number of compounds. One of these is 2,4-dihydroxybenzoic acid which is found in higher quantities in shaded teas, adding to their sweetness.

Aromas of Tea

Tea is jam-packed with aromatic compounds, with even more being produced through the various stages and styles of processing. Here are some of the most prevalent aromatic compounds in Japanese green teas:

• Dimethyl sulphide: marine, nori aroma
• β-ionone: floral aroma that only about 50% of people can detect
• Nerolidol: fresh, green aroma
• Safranal: like its name suggests, a saffron aroma
• β-damascenone: a sweet rosy/fruity aroma
• Benzaldehyde: almond/fruit aroma
• Benzyl alcohol: rosy/stonefruit aroma
• 2-phenylethanol: rosy aroma, but when combined with β-damascenone creates a honeyed aroma
• Geraniol: rosy aroma
• Cis-3-hexenol: fresh, green, spring aroma
• Cis-3-hexenal: even stronger green, grassy aroma, part of the ‘shincha aroma’
• Linalool: various floral aromas in different forms
• Jasmine Lactone: stonefruit, peach aromas
• Limonene: citrus aroma
• Coumarin: sakura, vanilla, cinnamon aromas
• Pyrazines: spicy or roasty aroma (especially in houjicha)

These are just some of the hundreds of chemicals that give tea its various aromas and tastes. To learn more about how processing is used to create the various styles and types of tea, read our post that explores the wide world of Japanese teas.

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References

Tea: A Nerd’s Eye View by Virginia Utermohlen Lovelace

Tetsuhisa Goto; Bulletin of the Tea Research Station (1994)