Why does my fruit tea change colour?

Because most red fruit teas are, quite literally, a pH indicator. The red comes from anthocyanins — the pigments in hibiscus, berries, blackcurrant and red grape — and anthocyanins change colour with acidity:

So a hibiscus tea that glowed ruby at your friend's house and comes out dull purple in yours has not gone off. Your tap water is harder and more alkaline than theirs.

The one-second test

Squeeze a little lemon into the cup. If the colour springs back to bright pink or red, it was pH, not a fault. That is also the easiest fix: a slice of lemon in the pot, or a filter jug for the kettle water.

Butterfly pea flower is the extreme version of the same effect — a deep blue infusion that turns purple the moment lemon hits it. Same chemistry, more dramatic.

Other reasons the colour shifts

• Hard water. Calcium and a higher pH dull everything, tea included. See tea in hard water.
• Standing. Anthocyanins fade with time, heat and light. A jug of iced fruit tea left in the sun loses its colour by the afternoon.
• Iron. Traces of iron from an old kettle or a cast-iron pot can turn fruit teas grey-black.
• Steeping time. Longer brewing extracts more pigment, so the same tea can look pale at two minutes and deep at six.
• The blend itself. A "berry" tea may be mostly hibiscus and rosehip, which is where the red really comes from. Read the ingredients — see fruit tea explained.

Is a colour change a problem?

No. It is a pigment responding to its surroundings, not a sign of spoilage. Judge a fruit tea by its smell and taste: musty or fermented smells mean bin it, colour alone does not.

What the colour does tell you is something about your water — and if your fruit teas look dull, your black tea is probably tasting duller than it should too. Hibiscus tea is the most colour-sensitive of the common ingredients.

Getting a brighter cup

1. Use filtered water if yours is hard.
2. Add a squeeze of lemon, or pick a blend with citrus or berry acidity in it.
3. Brew it in glass if you like the look — you cannot see any of this in a mug.
4. Drink it fresh; serve iced teas the day you make them.

Common questions

Why did my hibiscus tea turn blue?
Alkaline water. Add lemon and watch it go pink again.

Does the colour change affect the taste?
Not directly, though the same hard water that dulls the colour also flattens the flavour.

Is blue tea a different plant?
Butterfly pea flower is a different plant, naturally blue and famous for the lemon trick. Blue-ish hibiscus is just chemistry.

My fruit tea is brown, not red. Why?
Either the blend has little anthocyanin in it (apple, rosehip and orange are brownish), or it has aged. Check the ingredients first.

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