pouring-milk-cup-tea-18525536.jpgTea is a refreshing beverage for all seasons, for people of all regions and all ages. We have some of the most wonderful conversations over a cup of tea. Whether at home, school, or work we all take several tea breaks during the day. Let us make this conversation about chemistry.

There are many different kinds of tea, but they are all derived from just one plant Camellia sinensis. The taste and look of tea is often modified by the addition of sugar, milk, lemon, ice etc.

The unique taste of tea is due to the remarkable content of various chemical compounds. Polyphenols and flavonoids present in tea get rid of dangerous free radicals; the quinones contribute to the aroma, and thearubigens (also a polyphenol) and volatile oils contribute to the taste and the colour of tea.

Milk is the most popular addition to the black tea. Phenolic compounds present in tea binds with milk proteins. This will reduce the astringent taste, and smoothen the tea.  Additon of lemon juice gives a sharp and fresh taste to tea. The strong acidic nature of lemon juice releases hydrogen ions which are taken up by thearubigines thereby making them appear in lighter colour. Addition of ice to tea results in the formation of complex between caffeine and theaflavin (another polyphenol).

Other vital compounds in tea include amino acids, vitamins, minerals, and stimulants such as theine, theobromine and theophylline.  Theine and caffeine are identical methyl xanthines that are chemically related to the nucleotide bases Adenine and Guanine. When theine gets metabolized, theobromine and theophylline are its products. These xanthine alkaloids relax the muscle tone making us calm, and hence we see monks drinking tea as a way to increase the focus on meditation, making it a medication for meditation. Although tea has medical benefits, like anti-bacterial, anti-inflammatory properties along with healing cavities, children should have tea in limits due to the stimulants like theine. Green tea and herbal teas are devoid of theine but look for the signs before having tea.

Enough Chemistry I guess for today.

Contributed by Dr. Ramars Amanchy, CSIR-IICT.