Of course, some of us may like that taste, and tea processing can amp it up. After the new leaves and buds have been plucked from a bush, they are laid out to dry. How long they lie again depends on the kind of tea intended. For green teas, the leaves are almost immediately tossed in a hot pan or steamed (tea might look like the rawest of edibles, but it is actually cooked, or at least heat-treated). An oolong results when the leaves are dried a little, bruised and only then cooked. And a black tea – the most popular variant, accounting for 78% of the tea drunk world-wide – results when the bruised leaves dry quite a long while before being finished in the pan.

What’s behind all this is that as the tea leaves are drying, enzymes native to the tea plant are busily transforming simple molecules into more complex ones. The longer the tea spends drying, the longer those enzymes have to work – and the more these molecules build up in the tea leaves. The most famous in tea-chemistry circles is probably theaflavin, a tangle of carbon rings responsible for some of the ruddy colour of black teas as well as some of the astringency.

Firing the tea leaves calls the process to a halt by destroying the enzymes. As a result, there’s very little theaflavin and related molecules in, say, green teas. But aside from polyphenols, hundreds of other compounds build up in the tea over time; their roles in crafting tea’s bouquet and taste are not yet clear. Regardless, the end result is a different chemical profile for each kind of tea.