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  • Confusing coffee and milk temperature

    This little discussion on the right coffee temperature in Fairfax media has the confusing assertion that milk boils at 86 degrees ??? The little thermometer I have in the jug has a red mark from 60 onwards, I like my milk based coffee hot but not so it scalds the upper part of my mouth, could that happen with milk at 65 degrees and pre-heated cups?

    Also, those who drink a black coffee, if it is extracted at 92-96 degrees, how do you know when it is at your preferred drinking temperature, does a snob measure that?

    http://www.goodfood.com.au/good-food...318-2ga4b.html

  • #2
    Anyone who suggests that milk boils at 86 degrees obviously failed basic chemistry. Milk is predominately water... and we all know that pure water boils at 100 degrees C. In the same way that adding salt to a pot of boiling water raises its boiling point, the fats, proteins and sugars present in the milk also raise its boiling point and, therefore the boiling point of milk MUST be higher than 100 degrees... albeit only slightly above. Having said all that, milk steamed beyond 70 degrees will be very uncomfortable to drink and that is why milk heated between 60 and 65 degrees pretty much hots the spot... and... yes... a pre-heated cup will help keep it there. The reason that milk breaks down when it is being steamed beyond 70 degrees (and will completely collapse at around 86 degrees) is because the temp of the steam, and the steam wand, is hotter than 100 degrees due to its being under pressure (usually around 1.1 to 1.2 atm) and the milk molecules immediately in contact with the steam and/or steam wand are being subject to temps beyond the boiling point of milk and this contributes to the collapse of the proteins in the milk even when the average temp of the milk is below its boiling point. Hope this helps.

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    • #3
      Re: Confusing coffee and milk temperature

      Ive always read it was 56ºC.

      I like mine on the warm side, so I can drink it straight away. My wife always complains its too cold

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      • #4
        I'm sure there is a standard, however when making coffee at home it's an individual choice. I don't like mine cold but I sure don't like mine way to hot either

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        • #5
          Re: Confusing coffee and milk temperature

          Originally posted by Vinitasse View Post
          Anyone who suggests that milk boils at 86 degrees obviously failed basic chemistry. Milk is predominately water... and we all know that pure water boils at 100 degrees C. In the same way that adding salt to a pot of boiling water raises its boiling point, the fats, proteins and sugars present in the milk also raise its boiling point and, therefore the boiling point of milk MUST be higher than 100 degrees... albeit only slightly above.
          Actually, this is not quite correct. Milk is a colloid, not a pure solution. This means the fats are actually small solid or liquid particles, surrounded by (mostly) water. I imagine some of the sugars and proteins have hydrophilic ends and hydrophobic ends, which bridge the interface and stabilise the colloid and prevent the fat coalescing. In addition, a mixture of two immiscible liquids will actually have a boiling point below that of either pure liquid.

          I havent checked to see what the boiling point of milk is, so it could well be over 100ºC, but your justification was based on a partly flawed assumption that milk is a solution.

          In any case, stretching the milk is not boiling it. We are adding small particles of air to the colloid (which makes it somewhere between a colloidal emulsion and a foam, if memory serves). We are probably also changing the protein structure, and possibly the size of the fat particles.
          My 2c.
          Last edited by MrJack; 21 March 2013, 11:45 AM.

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          • #6
            Originally posted by MrJack View Post
            Actually, this is not quite correct. Milk is a colloid, not a pure solution. This means the fats are actually small solid or liquid particles, surrounded by (mostly) water. I imagine some of the sugars and proteins have hydrophilic ends and hydrophobic ends, which bridge the interface and stabilise the colloid and prevent the fat coalescing. In addition, a solution of two liquids will actually have a boiling point below that of either pure liquid.

            I havent checked to see what the boiling point of milk is, so it could well be over 100ºC, but your justification was based on a partly flawed assumption that milk is a solution.

            In any case, stretching the milk is not boiling it. We are adding small particles of air to the colloid (which makes it somewhere between a colloidal emulsion and a foam, if memory serves). We are probably also changing the protein structure, and possibly the size of the fat particles.
            My 2c.
            Actually... I believe that milk is a complex solution which includes both dissolved substances, and colloidal suspensions.

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            • #7
              Originally posted by MrJack View Post
              Actually, this is not quite correct. Milk is a colloid, not a pure solution. This means the fats are actually small solid or liquid particles, surrounded by (mostly) water. I imagine some of the sugars and proteins have hydrophilic ends and hydrophobic ends, which bridge the interface and stabilise the colloid and prevent the fat coalescing. In addition, a solution of two liquids will actually have a boiling point below that of either pure liquid.

              I havent checked to see what the boiling point of milk is, so it could well be over 100ºC, but your justification was based on a partly flawed assumption that milk is a solution.

              In any case, stretching the milk is not boiling it. We are adding small particles of air to the colloid (which makes it somewhere between a colloidal emulsion and a foam, if memory serves). We are probably also changing the protein structure, and possibly the size of the fat particles.
              My 2c.
              Hmmmm, think I'll accept the explanation offered by Vinitasse as being near enough, at least I could understand what he was on about.

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              • #8
                Re: Confusing coffee and milk temperature

                Certainly is. From a quick google, it seems like the exact structure of the micelles (colloidal particles) is somewhat debated.

                Ive corrected a sentence in my previous post about boiling point of mixed liquids also.

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                • #9
                  Re: Confusing coffee and milk temperature

                  Originally posted by Yelta View Post
                  Hmmmm, think I'll accept the explanation offered by Vinitasse as being near enough, at least I could understand what he was on about.
                  Fair enough, sometimes less is more.
                  I was just trying to add some detail to the discussion; almost correct statements have a way of becoming gospel on the internet.

                  Much like the way the simplified highschool science "rules" cause all sorts of problems at university, where you have to unlearn them.

                  The way I picture milk is lots of tiny bubbles of fat floating in water.

                  The key point really is dont boil your milk!

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                  • #10
                    Just to add a little more "internet inteligence" ..
                    The boiling point of milk is close to the boiling point of water, which is 100°C at sea level, but milk contains additional molecules in it, so its boiling point is slightly higher. Exactly how much higher depends on the exact chemical composition of the milk,
                    so there isn't a standard boiling point of milk that you can look up!
                    However, it's only a fraction of a degree, so the boiling point is very close to that of water. As with water, the boiling point of milk is affected by atmospheric pressure, so the boiling point is highest at sea level and lower up on a mountain.

                    Why Is the Boiling Point Higher?
                    The boiling point of milk is higher than the boiling point of water because of a phenomenon called boiling point elevation. Whenever a non-volatile chemical is dissolved in a liquid, the increased number of particles in the liquid causes it to boil at a higher temperature. You can think of milk as water that contains salts, sugars, fats, and other molecules. Just as salt water boils at a slightly higher temperature than pure water, milk boils at a slightly higher temperature, too. It's not a huge temperature difference, though, so expect milk to boil about as quickly as water.

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                    • #11
                      I'm pretty sure I already said that

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                      • #12
                        Anybody who believes **ANYTHING** without taking into account the usual rules regarding utilising information, will likely do bad things to their level of ignorance!

                        (Rant-on) Newspapers are designed (now) for making the owners rich and influential and not for providing information or intelligence/knowledge. IMO you actually get more ignorant the more you read them. Except for the funnies. (Rant-off)

                        Greg

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                        • #13
                          none of these problems exist when drinking espresso

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                          • #14
                            Well it made me think and I actually measured a shot (black) in a pre-heated cup and found that it was only around 45 degrees, lower than I expected! Maybe the article was not that special but I'm definitely less ignorant

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                            • #15
                              Espressos are meant to be drunk right away, not lingered over a long conversation. Since the brew temperature has to be ideally in the low 90sC, and the volume is very small, up to 60 ml, it will cool very very quickly otherwise.

                              Taking the temperature of espresso in a warmed cup will yield imperfect readings. The temperature in the low 90s is the temperature of the water just before it hits the puck. From there on, the room-temperature grounds will draw heat away. By the time the brew falls through the air, and into the cup, even more degrees will be lost.

                              Milk? I believe the right temperature is one which is comfortable to drink. Scalding certainly is not comfortable, and I see no good reason to wait...wait...waiting... for it to drop to that drinkable temperature.

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