Swetha Sivakumar spills the tea on tannins

A good chaiwala adds spoons of black tea to boiling milk. He then lets it come to a rolling boil over and over. Adds some sugar. Then some fancy stirring and pouring action. A dash of powdered chai masala. And in a few moments, the delicious, aromatic chai is ready.

Try as one might, it’s impossible to get the same flavour at home. Or is it? It’s easier to make good chai once one understands the science of each step, and how the recipe hinges on taming the tannins in the tea.

Tannins are water-soluble polyphenols found in a lot of foods: tea leaves, coffee beans, red wine, cloves, pomegranate, betel nut. If a food makes one’s mouth go dry after consuming it, it typically contains tannins.

These biomolecules add flavour, but also bitterness and astringency. They’re like over-enthusiastic house guests – a lot of fun at first, but soon enough one just wants them to be quiet and let others do a bit of the talking. The “others” here are the aroma compounds, and black tea has nearly 600 of these, three times as many as green tea.This disparity is astonishing considering that both teas (all teas, in fact) come from the same plant, Camellia sinensis.

When processing black tea, however, the leaves are crushed and fully oxidised. This enzymatic action, along with the step of roasting before packaging, creates a large number of new aroma compounds, a richer colour; but also a lot of tannins.

The issue now is that it takes two to five minutes for black tea to release its complex flavour and aroma molecules in boiling water. Meanwhile, the tannins are taking over. They have to somehow be quieted, and a good way to do this is with milk.

You see, tannins have a weakness. They’re always looking for proteins to bond with. The whey protein in milk provides a mellowing effect. As it starts unravelling at about 78 degrees Celsius, it binds readily with the tannins as they leach out of the tea. This is why the chaiwala can boil the tea leaves in milk for so long, without fear of the mix becoming overly bitter.

Now for the frothing. While it’s an impressive theatrical touch, swishing the tea from glass to glass at great heights, this motion serves a purpose too. Suffusing oxygen into the chai has the effect of further softening the flavour of the tannins (similar to the effect of decanting red wine to let it breathe).

The addition of sugar while the mix is boiling further mellows the strong and bitter notes. Sugar, being hydrophilic, hogs the water molecules around it, thus leaving less water for the tea particles (or any other aroma molecules) to infuse. This is why, if one asks for kadak chai, the chaiwala will likely add the sugar only at the end, and not while brewing.

Finally, for the aroma, there is the spice mix (ginger, cinnamon, cloves, pepper, fennel; there are no wrong answers here). We know that taste is just one aspect of flavour. Our sense of smell is a far more powerful driver. This is where the spices come in, conveying new flavour notes to the brain.

When using a spice mix in chai at home, there are a couple of things to watch out for. Fresh ginger contains an enzyme called zingipain that curdles milk, unless one deactivates it by bringing the mix to a boil. Cardamom pairs really well with chai because most of the flavour compounds in this spice dissolve far better in fat (from the milk) than in water. Go easy on tannin-heavy spices such as cinnamon and cloves, for obvious reasons.

For chaiwalas, however, time is money, so they use a powdered spice mix that creates an increased surface area and allows the aromas to be released more quickly. They add this towards the end so that the volatile fragrances are fresh and enticing as one brings the chai to one’s mouth.

It’s years of experience that tell the chaiwala what to do. Now, you have the secrets too.