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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 hot tea "scalds the milk".

Won't having 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.)

billpg
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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. – Goodbye Stack Exchange May 28 '12 at 16:21
  • Guardian newspaper Notes & Queries - http://www.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 09:26
  • 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
  • @Keith - That a normal human with normally functioning taste sense could tell the difference? – billpg May 30 '12 at 18:13
  • As an American, I can say that adding milk to your tea ruins it, regardless of the timing. :) – Flimzy Jul 31 '14 at 14:34
  • @SamIAm: Water temperature is *always* less than boiling. Once it reaches boiling, it's no longer water. – Flimzy Jul 31 '14 at 14:35
  • @Flimzy That's not true at all. Depending on the stability of the water, nucleation sites, etc. you can super-heat water about the boiling point. Even in absence of funny stuff like that, the boiling point is an equilibrium temperature and pressures where you can have water and steam. When water is 100C (at 1Atm), at any instant, some will become steam and some will stay water. Source: I'm a mechanical engineer. – William Grobman Jul 31 '14 at 18:46
  • @WilliamGrobman: You can change the boiling point of water... but you cannot heat "water" beyond the boiling point. You can also change the phase of the mater such that it is a superheated gas, but it's not water (in the liquid sense) in that state any more, either. Source: [Wikipedia](https://en.wikipedia.org/wiki/Boiling_point). But more to the point, in cooking (which is far more relevant to this question than corner cases of mechanical engineering) the fact that you cannot heat water above the boiling point is often used for temperature control. Source: I know how to cook. – Flimzy Jul 31 '14 at 19:43
  • @Flimzy Water can absolutely be heated above the boiling point for its given pressure. Just one example, I work in thermal inkjet printing. The boiling point of water in our nozzles in 100C. When a resistor fires, the rapid heating of the water in a smooth silicon vessel can cause the water to reach temperatures well over 200C before the water boils and ejects a drop. Similarly, take a really smooth glass container and microwave it; you can often heat above 100C and get flash boiling if you disturb it. Boiling is not as simple or cut and dry as you're making it out. – William Grobman Jul 31 '14 at 19:58
  • It's somewhat a stochastic process that's determined by bubble nucleation and stability. – William Grobman Jul 31 '14 at 19:59
  • @WilliamGrobman: Well, I thought that the state of the matter was no longer liquid in that case, but I trust you know more than I. Regardless, nobody's heating their tea or cooking other liquids under such conditions. – Flimzy Jul 31 '14 at 20:45
  • @Flimzy I think you're right but I don't know that you can't superheat in a kettle. Here's an interesting article if you're interested: http://en.wikipedia.org/wiki/Superheating – William Grobman Jul 31 '14 at 21:08

2 Answers2

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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

Tom77
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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
  • @billpg Yeah, let's question the Royal Society of Chemistry. Because random guys on the internet always know much more than scientists – DJClayworth May 29 '12 at 03:32
  • @billpg Denaturation of whey proteins in milk starts at 70 degrees: http://pubs.acs.org/doi/abs/10.1021/jf00012a013 I'm not sure that anyone has specifically tested order of operations for tea. I'm also not entirely sure whether or not the Royal Society for Chemistry release is a joke. Most of it seems to be on face value. – John Lyon May 29 '12 at 04:14
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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 07:13
  • @billpg, the *other* reason for putting the milk in first is that you don't *need* to stir it afterwards, the kinetic energy of the water generally does the stirring for you. – Benjol May 29 '12 at 09:26
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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 01 '12 at 02:06
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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
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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.

Michael Greinecker
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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
  • I gave the green tick to this one (despite the votes) as the answer actually cites a study. – billpg Jul 31 '14 at 15:05