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I once had a conversation with a colleague about the correct way to make tea. He stated that adding milk to boiling hot tea "scalds the milk".

Won't having boiling hot water poured into some milk "scald" it just as much?

(For the record, I've never been able to tell the difference. I'm amazed so many people are so passionate about this question.)

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I always thought the best tea was made with water temperature less than boiling. –  Sam I Am May 28 '12 at 16:20
    
Anyone have a link for this claim? Would hate to see this closed for being a non-notable claim. –  neilfein May 28 '12 at 16:21
    
Guardian newspaper Notes & Queries - guardian.co.uk/notesandqueries/query/0,,-1400,00.html –  Tom77 May 28 '12 at 17:07
    
If your tea is boiling, your doing something wrong either way... –  Benjol May 29 '12 at 9:26
    
Define 'significant'? It's one thing for 70-80 deg water to denature some proportion of the the milk in some way, but wouldn't it have to be in sufficient quantities for the human pallet to spot it? And isn't it relative? Wouldn't the type of milk or tea make more of a difference than the way it's added? –  Keith May 29 '12 at 23:05

2 Answers 2

Source - How to make a Perfect Cup of Tea, Royal Society of Chemistry

Milk should be added before the tea, because denaturation (degradation) of milk proteins is liable to occur if milk encounters temperatures above 75°C. If milk is poured into hot tea, individual drops separate from the bulk of the milk and come into contact with the high temperatures of the tea for enough time for significant denaturation to occur. This is much less likely to happen if hot water is added to the milk.

The British Standard for making tea (BS 6008) also states that tea should be added after the milk:

Prepare the liquor as described in 7.2.1 but pour it into the bowl after the milk, in order to avoid scalding the milk

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Just for completeness, it is also the ISO (International) standard 3103. I'm enjoying imagining how much more relaxed the audits are for this standard compared to the others. The other source is a press release, and isn't peer reviewed. –  Oddthinking May 28 '12 at 10:43
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Thank you, but I'm (respectfully) not buying this. Has anyone checked the chemistry involved? Is there really much less break-down of milk proteins when hot water has been poured into milk and the mixture then stirred? (vs pouring milk into hot water and then stirring the mixture.) –  billpg May 28 '12 at 12:03
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Yes! Let's question the Royal Society of Chemistry! I do not accept arguments from authority. I'll accept it if they've done a proper study, but they don't cite any. –  billpg May 29 '12 at 7:13
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I'm wondering if this holds true for teabags. I've noticed that it is hard to get a good cup of tea when the milk is added first when using teabags. I had assumed it was due to the milk coating the teabag and not allowing as much diffusion. –  Tim Scanlon Jun 1 '12 at 2:06
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@TimScanlon indeed, also when you use a teabag you brew the tea for a length of time during which the water cools down. Adding the milk after exposes it to less extremes of temperature than pouring the water in first. This standard is for making tea from a teapot, not with a teabag. What we need is a tea-bag standard ISO! –  Nick Dec 13 '12 at 13:47

Yes. The demonstration of this fact is actually a famous anecdote in the history of statistics. Ronald A. Fisher, one of the towering figures in the history of statistics, gave the case as an example in the second chapter of his book The Design of Experiments (1951), without mentioning it being based on a true story. Some references can be found on the Wikipedia page for Lady tasting tea. A detailed description of the experiment can be found here, where one can find the following account from R. A. Fisher: The Life of a Scientist (1978) by Box:

Already, quite soon after he had come to Rothamstead, his presence had transformed one commonplace tea time to an historic event. It happened one afternoon when he drew a cup of tea from the urn and offered it to the lady beside him, Dr. B. Muriel Bristol, an algologist. She declined it, stating that she preferred a cup into which the milk had been poured first. “Nonsense,” returned Fisher, smiling, “Surely it makes no difference.” But she maintained, with emphasis, that of course it did. From just behind, a voice suggested, “Let’s test her.” It was William Roach who was not long afterward to marry Miss Bristol. Immediately, they embarked on the preliminaries of the experiment, Roach assisting with the cups and exulting that Miss Bristol divined correctly more than enough of those cups into which tea had been poured first to prove her case.

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I totally remember that exact same story, but for some reason I recall the outcome being the opposite - that the lady couldn't taste the difference. Weird. –  Tacroy May 29 '12 at 16:40

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