What is the white foam that builds up when I make tea?
I microwave water in order to make tea. After it is microwaved and I drop the tea bag(green tea) into the water, thick white foam builds up on the top.
What is it and should I worry about drinking it?
Best Answer
When you boil water in a cup in a microwave, it will often boil without forming bubbles, because unlike a kettle with a rough heating element or inner surface, a clean ceramic cup has few nucleation points. Nucleation points allow pockets of gas to form, which become bubbles as the water boils.
When you add the teabag to the hot water, you are essentially introducing thousands of nucleation points very quickly, and so lots bubbles form very quickly - your foam. You should exercise caution when heating water this way prior to adding a teabag, as if you heat it for too long it can superheat, and will boil explosively out of the mug when you add the teabag.
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What is the film on top of my tea?
The oily film on black tea is mostly made of some of the compounds in the tea \u2013 particularly, molecules called polyphenols \u2013 and calcium carbonate. Calcium carbonate is present in tap water, but its content varies from place to place. A higher concentration of calcium carbonate will create a thicker film.Is tea supposed to be foamy?
It's a result of a chemical reaction when hot water comes in contact with the leaves. The extraction of proteins and amino acids will result in foam. Because these are healthy components in tea, some people argue that the more foam or scum you see, the more healthy the tea actually is.How you've been making tea WRONG your entire life - BBC
More answers regarding what is the white foam that builds up when I make tea?
Answer 2
Tannins produce foam in tea, and also streams and rivers.
Answer 3
There's nothing to worry about when you see the foam appear. When hot water comes in contact with tea, it extracts the amino acids and proteins that result in such foam.
The reason that you get more foam on the surface is when you microwave the water is perhaps dip the bag in hot water. When you put the tea bag in the cup first, part of the bubbles that appear will dissolve due to the moving water. Try to see if this makes a difference.
Check this page for more information: https://www.teasenz.com/chinese-tea/foam-surface-tea.html
Answer 4
This may not be direct answer to your question about what the foam is made up of. But when it forms and how to avoid it.
This often happens if the water is not warm enough.
If you like to avoid it, you can try these steps:
Most tea leaves should be placed in water near boiling point. That's 95C (or 200F) for black tea and 90C for Green tea. If you're not near sea level altitude just make sure the water reaches boiling point.
Pour the boiling water over the tea bag already placed in your cup. Dunking the dry tea-bag into hot water can lead to the issue ElendilTheTall talks about as well as foam.
Answer 5
The "white" foam is caused by denatured proteins in the tea leaves when heated. Same when you boil meat, eggs or fish.
Sources: Stack Exchange - This article follows the attribution requirements of Stack Exchange and is licensed under CC BY-SA 3.0.
Images: Decha Huayyai, roberto carrafa, Dynamic Wang, Pixabay