... as applied to cooking.
The CC brews a cup of coffee, and it's piping hot. He needs it to cool it ASAP. Everyone knows that the CC is one hellasiously impatient fugger.
Wait for it to get cooler, and then add ice cold milk?
Or add ice cold milk, and then wait for it to cool?
Which one, and why?
C'mon scientists; put your money where your science is.
Saturday, February 9, 2008
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The two men sat across from one another at one of New York's finest coffeeshops. The taller of the pair remarked "Here it comes." His companion quicky bent and withdrew something from his briefcase.
While both men watched intently, a harried-looking waiter strode briskly up to the table and deposited, in quick succession,
two clear mugs of steaming black coffee, and a bucket of ice containing a silver cow-shaped creamer. As he turned smoothly from the table to leave, a most curious and frenetic scene unfolded.
His arm uncoiling and striking like a snake, the taller man seized the creamer, poured a shockingly precise dollop into his mug, and replaced the creamer in the ice bucket. Meanwhile, his companion, paying no mind to this strange behaviour, calmly clipped a small thermometer to the side of his own mug, so that the silvery head was just covered by the dark coffee within. He then leaned far forward in his chair and peered intently at the reading.
Taut seconds passed. The taller man gave his coffee a perfunctory stir with his spoon. He raised it nervously to his lips and blew once. Twice.
"For fuck's sake, no blowing!" his companion hissed. "We explicitly said no artificial convection!"
"Sorry."
"Well, don't do it again, bitch!"
"Do you want me to burn my lips?"
"I don't give a fuck what you do to your lips! Oh shit!" He leaped up. "170C already!" He grabbed the creamer. "That's the magic fucking number! (I ran a simulation all night to calculate that.)" He poured a precise dollop of cream into his mug.
Both men raised mugs to lips and tilted them back. A sudden hush fell over the room.
The giant shook his head, setting his mug back down. "Mine's still too hot."
His companion gleefully threw his head back, downing his entire coffee in one shot. "Aaaaaaaaiiiiiiiiieeeeeeeeeaaaaaaaaaaahhhh!"
he screamed, leaping from his chair and dashing around the room while tears streamed from his eyes.
"Too hot?" his companion asked, when he had sat down again.
"Do, id wad perfecdt, bidch." He licked his lips with some effort. "Delicious. Ead by fuckig shordts!" He stood abruptly. "Godda go. Beatig."
"Well, you won. I guess I'm paying."
"Dad's ride bee-yatch! Shoulda leard some goddabbed physics. Yeehaw!" He strode from the shop, startling several New Yorkers with his speed.
Smiling ruefully, the other man sat back in his chair and blew some more steam from his mug.
About an hour later, he still sat in the same position. Gone was the small smile from his face. No more chuckles passed his lips. Unshed tears glistened in his eyes.
For at last he truly understood the depth of his folly. He had added the icy cream too soon. In all probability, the heat death of the universe would come well before his coffee reached a drinkable temperature.
you should let the coffee cool before adding milk. The higher the temperature of the coffee the more it coagulates the milk (given that coffee is acidic - even your cold pressed one is slightly acidic).
That ends up with the Casein (the phospho-protein in milk) ending up on your tongue as a white coating when you finish the coffee. The cooler the coffee when the milk is added the less casein is deposited on your tongue ... resulting in a smoother finish :-)
Depends..... :o)
... on what?
Depends on what happens chemically when the milk is added to the hot coffee. If it does something like curdle or form a layer of something on the top, it will affect the evaporation rate of the water at the surface, which will affect your cooling rate.
Let's play physicist and make some assumptions:
1) The milk doesn't do anything special and we're just dealing with water into water.
2) Everything else between the two experiments isn't changed (surface area of the liquid, humidity above the liquid, air currents, ambient temperature, etc.)
3) There is enough circulation that the temperature, humidity above the liquid remains constant.
Okay, now we set up two experiments, one where the icy water is added immediately and another where it is added after some time. Since the cooling rate of the water will almost solely depend on the evaporation rate of the water, and the evaporation rate should depend on a bunch of things held constant (area, humidity, ambient temp, etc.) as well as exponentially depending on the difference between the temperature of the liquid at the surface and the ambient temperature. Since it's an exponential decay depending on the same parameter (delta-T), the temperature of the water with the initial lower temperature (the one with added milk) will always be lower than the other one at any given time.
So, add your milk (the skimmer the better), and rest easy knowing that your coffee will come to your optimal temperature faster than the fool who is waiting for it to cool first before adding.
Of course, if adding the milk does decrease the evaporation rate in a way other than predicted by adding an equivalent volume of cold water, then there could be an optimal time to add the milk, depending on how long after you got it you wanted to drink it.
How does that sound?
You don't need any assumptions.
The same answer holds with boiling hot water, and ice cold water (where no assumptions need apply.)
It's elementary thermodynamics not fancy biochemistry. :-)
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