chemistry - Why doesn't espresso make milk curdle?

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Feil
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chemistry - Why doesn't espresso make milk curdle?

Postby Feil » 2012-10-02 08:58pm

How come milk curdles when you put acid in it, but not when you mix it with a low pH non-acid substance like espresso? Or, put another way, what is it about acid that makes milk curdle, since it doesn't appear to be the pH?

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Memnon
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Re: chemistry - Why doesn't espresso make milk curdle?

Postby Memnon » 2012-10-02 09:27pm

Coffee has a pH of around 5, which is very mild.
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Re: chemistry - Why doesn't espresso make milk curdle?

Postby Simon_Jester » 2012-10-02 11:20pm

There's no such thing as a non-acid with low pH; that's how you define an acid in the first place.

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Re: chemistry - Why doesn't espresso make milk curdle?

Postby Darth Tedious » 2012-10-02 11:43pm

Hey it's totally propaganda for the HealthWise Corporation, but here's the Ph for a bunch of different coffee brands.
http://www.healthwisecoffee.com/blog/?page_id=89
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Re: chemistry - Why doesn't espresso make milk curdle?

Postby Knife » 2012-10-03 12:13am

IIRC, the acid denatures the protein in the milk, causing the protein chains to 'unwind' and thus make odd shapes like the curds, and solidifying. Higher the PH the more reactive? Something along those lines. A substance with a PH pretty close to the milk won't do that.
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Re: chemistry - Why doesn't espresso make milk curdle?

Postby Darth Tedious » 2012-10-03 01:40am

7 is Ph neutral, lower than that is acidic, so lower = more reactive in this case.
It would seem that 5 is simply not acidic enough to react with milk.
Keep in mind that Ph is logarithmic, so each number below 7 is 10x as acidic.
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Re: chemistry - Why doesn't espresso make milk curdle?

Postby Knife » 2012-10-03 09:46am

Fair enough, I meant 'higher' as in 'more acidic'. But yes, you are correct.
They say, "the tree of liberty must be watered with the blood of tyrants and patriots." I suppose it never occurred to them that they are the tyrants, not the patriots. Those weapons are not being used to fight some kind of tyranny; they are bringing them to an event where people are getting together to talk. -Mike Wong

But as far as board culture in general, I do think that young male overaggression is a contributing factor to the general atmosphere of hostility. It's not SOS and the Mess throwing hand grenades all over the forum- Red

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Re: chemistry - Why doesn't espresso make milk curdle?

Postby Feil » 2012-10-03 10:03am

Thanks all. :)


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