Pigment in tea is a class of coloured substances present in fresh leaves of tea tree and finished tea, it is the component that constitutes the appearance of tea colour, soup colour and leaf bottom colour, its content and changes play a vital role in the quality of tea.

 

Among the tea pigments, some are already present in the fresh leaves, which are called natural pigments in tea, and some are formed by oxidative condensation of some substances during processing. Tea pigments are usually divided into two categories: fat-soluble pigments and water-soluble pigments.

 

Fat-soluble pigments mainly play a role in the colour of dried tea leaves and the colour of the underside of the leaves, while water-soluble pigments mainly have an effect on the tea broth.

 

Excluding unnatural added pigments, there are two types of pigments in tea, natural pigments and processed pigments, which we will introduce for you respectively.

 

 

Natural Colours in Tea

 

(i) Fat-soluble pigments

Including chlorophyll and carotenoids, insoluble in water, soluble in non-polar organic solvents.

 

Chlorophylls

Chlorophyll is divided into chlorophyll a and chlorophyll b. Chlorophyll in fresh tea leaves accounts for about 0.3% to 0.8% of the dry weight of tea leaves. The content of chlorophyll a is 2~3 times that of chlorophyll b. The total amount of chlorophyll depends on the variety and season. The total amount of chlorophyll varies greatly according to varieties, seasons and maturity. The chlorophyll content of fresh leaves with yellow-green leaves is low, and the content of fresh leaves with dark green leaves is high.

 

In general, green tea with high chlorophyll content is preferred, black tea, oolong, white tea, yellow tea and other requirements for chlorophyll content is lower than green tea.

 

Carotenoids

Carotenoids are a class of coloured compounds that range from yellow to orange-red. There are 17 carotenoid compounds found in tea, which are classified into two categories: carotenoids and lutein. Carotenoids, especially during black tea processing, are subject to extensive oxidative degradation to form a series of compounds of the violet rotenoid family.Omori (1978) found that the addition of β-carotene during black tea processing was beneficial to the colour and aroma of black tea.

 

(ii) Water-soluble pigments

Water-soluble pigment is a general term for colouring substances that can be dissolved in water. It generally refers to the oxidation products of anthocyanins, anthocyanins and catechins. Tea has been found in dozens of flower flavonoids, anthocyanins, is the main body of water-soluble pigments in tea.

 

Flavonoids, also known as flavonoids, mainly including flavonols and flavonoids are two types of compounds, which are the components of tea polyphenols. It is an important part of green tea soup colour.

 

 

Colour pigments formed during tea processing

 

In the process of tea processing will form a variety of pigments, which constitute the characteristics of tea quality, play an important role in different types of tea. For example, during the processing of black tea, due to the oxidation of polyphenols, theaflavins and thearubigins are formed, making black tea with its quality characteristics.

Theaflavins

Theaflavins are a class of pigments with orange-yellow colour and astringency in black tea. It plays an important role in the intensity and freshness of the colour and aroma of black tea, and is also the main ingredient of the “bright” black tea broth colour, and is the main substance in the formation of the “golden circle” of black tea. High theaflavin content of black tea soup colour is golden yellow, high quality, extremely popular in the market.

 

RobertsE.A.H. pointed out that most of the reviewer’s assessment of the colour is affected by theaflavin, the higher the content, the better the brightness of the soup colour, golden yellow, the lower the content, the darker the soup colour. Theaflavin and caffeine, theobromine and other complexes, the lower the temperature shows the phenomenon of milk coagulation, is the tea soup “cold after muddy” one of the important factors.

 

In the 1990s, nine theaflavin components have been isolated: theaflavin 1a, 1b, 1c, theaflavin acid, etc. Hilton and Cloughley’s (1980) study showed that theaflavin content is positively correlated with the price of tea, through the measurement of the amount of theaflavin can be predicted by the black tea market price. Theaflavins have antiviral, lipid regulation, prevention of cardiovascular disease, and no toxic side effects.

 

Theaflavins

Theobromine is a complex class of reddish-brown phenolic compounds. The content in black tea is about 6% to 15% (dry weight). The substance is brownish red, soluble in water, water solution is acidic, weak irritation, is the main substance that constitutes the colour of black tea soup, involved in the formation of “cold after muddy”.

 

Tea brown pigment

Tea fucoxanthin is a kind of water-soluble non-dialysis high polymerisation of brown substances, its main components are polysaccharides, proteins, nucleic acids and polyphenols, further oxidised and polymerised by theaflavin and thearubigin, which is an important factor in the darkness of the black tea broth colour. Theaflavin is extracted from Pu-erh Tea (ripe tea) through modern physical technology, and has beneficial effects on the human body, such as lowering blood lipids and blood sugar.

 

There are many different colours in tea, which are beneficial to human health. However, outside abnormal additive pigments can cause damage to the human body, so when you buy tea, you should be careful to select and identify carefully.

 

Are there any added colourings?

How to recognise tea on the market

 

Dried Tea: Too Bright Colour

From a tea’s dry tea, we can tell a lot of things, such as the age and tenderness of the raw materials, and how good or bad the processing technology is. Similarly, we can also tell from a dried tea whether it has added colouring. Usually, dried tea with added colouring will look very bright, such as Biluochun with added lead chrome green, Jinjunmei with added sunset yellow, etc., all of which will be so bright as to be a bit unusual.

 

Aroma: Impure

Tea with added colouring will give the tea an unusual smell. If the tea leaves do not taste pure after brewing, there are strange smells, miscellaneous smells and other difficult to identify the taste, then these teas may be added flavouring or colouring.

 

Tea broth: cloudy and opaque

In general, the tea broth should be very clear, only a few improperly processed turbidity, or more hair tea varieties produced by the muck. The tea with added colouring will become cloudy after brewing, not the usual colour.

 

Different pigments form different qualities of tea, understanding the pigments in tea can help us intuitively choose tea, identify the authenticity of the tea, so that we can drink tea more healthily and enjoy life.