Why does milk thicken when whipped?

Discussion in 'Chemistry' started by stateofmind, Jul 5, 2009.

  1. Dub_ Strange loop Registered Senior Member

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    156
    Someone is a bit defensive.

    I can't post links yet -- apparently I need 20 posts before I can do that -- but here are some off site quotations:
    You were saying?
     
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  3. Asguard Kiss my dark side Valued Senior Member

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    http://wiki.answers.com/Q/What_are_the_difference_between_fats_and_oils


    "The difference between fats and oils is in their melting point. Fats tend to be solids at room temperature; oils tend to be liquid at room temperature. "
    http://www.healingmatters.com/fats.htm

    "The main distinction between fats and oils is whether they’re solid or liquid at room temperature, and this, as we’ll soon see, is based on differences in the structures of the fatty acids they contain."
    http://biology.clc.uc.edu/Courses/bio104/lipids.htm

    just because someone is to stupid to use the word LIPID correctly doesnt make you correct. Oils are NOT fats, they are related molicules but that doesnt make them the same, do some chem and work it out. Fats, oils and waxes are all LIPID molicules, not fat molicules
     
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  5. Dub_ Strange loop Registered Senior Member

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    Those "stupid people" are two dictionaries (which I used at your suggestion), the USDA, and then my last quote ironically is from the very same page that you used in your last quote! Your own source contradicts you: "unsaturated fats are liquid at room temperature."

    Here's what wiki has to say:
    In other words, oils are fats are lipids. They are fats with a lower melting point, as numerous sources have now indicated. If you still aren't convinced, read the nutrition label on any food oil.
     
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  7. ElectricFetus Sanity going, going, gone Valued Senior Member

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    18,142
    Can we leave it at low polarity triglycerides? I always figure creams a foam, that why it does what it does, just air plus water emulsion and surfactant (in this case more "surfactant" then water) and BAM foam.
     
  8. Orleander OH JOY!!!! Valued Senior Member

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    25,817
    and you need to admit cream is NOT a SOLID at room temp. Who the hell cares if its a fat or lipid or play-doh. IT'S NOT A SOLID!!!!!
     
  9. Tiassa Let us not launch the boat ... Staff Member

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    34,667
    Compassion, vernacular, and technical definitions

    Asguard

    Have some compassion, mate. I think part of the problem you're encountering is that you're using a more technical definition while others (especially Orleander) are applying a more vernacular context.

    To remove fats, lipids, oils, solids, and liquids from it for a moment, if you asked a hundred people to name a metal, how many would say iron? Gold? Silver? Probably a lot. How many, on the other hand, would say sodium or potassium? Probably fewer than those who would recognize mercury as a metal.

    Point being: The vernacular perspective does not always match the proper scientific or technical definition.

    And therein lies the main problem in communicating the point.
     
  10. Trippy ALEA IACTA EST Staff Member

    Messages:
    10,890
    From what I recall, all oils are also fats, but not all fats are oils.
    Oils are a sub group of fats.
    Fats are a sub group of Lipids.
    Yes, it's true that the difference between a fat and an oil is the melting point.
    From what I remember, the difference between canola oil, and canola oil spread is that (or it used to be that) some proportion of the polyunsaturated fats that ordinarly make up the canola oil have been hydrogenated, which changes the physical properties of the bulk substance.
    The greater the proportion of hydrogenation, the harder the spread, and the less healthy it is.

    Also, consider the diccerence between Elaidic Acid and Oleic Acid.

    Eladic Acid is Trans 9-Octadecenoic Acid
    Oleic acid is Cis 9-Octadecenoic Acid

    They're both 9-Octadecenoic acid, the difference is the isomer.
    Elaidic acid has a melting point of 46.5°C
    Oleic acid has a melting point of 4°C

    We would then expect Elaidic acid to form fats at room temperature, and Oleic acid to form oils.

    Now as far as Cream goes, according to Wikipedia, Half Cream is 12% butter fat, single cream is 18% butter fat, whipping cream is 35% butter fat, and clotted cream is 55% butter fat.

    Butter fat is in itself a complex mixture of fatty acids (again, from Wikipedia), but is typically:
    • Saturated fatty Acids:
      • Palmitic acid: 31%
      • Myristic acid: 12%
      • Stearic acid: 11%
      • Lower (at most 12 carbon atoms) saturated fatty acids: 11%
    • Unsaturated fatty Acids:
      • Oleic acid: 24%
      • Palmitoleic acid: 4%
      • Linoleic acid: 3%
      • Linolenic acid: 1%

    Now, bearing in mind that Butter fat is 54% saturated fatty acids, and 32% unsaturated fatty acids, and that saturated fatty acids are generally Solids.
    • Palmitic acid MP: 63-64°C
    • Myristic acid MP: 58.8 °C
    • Stearic acid MP: 69.9°C

    It is accurate in every sense to refer to Milk, and cream as being a colloidal suspension of solid fats in water - in that although it is fluid at room temperature (in the sense that it is capable of flowing to fill the bottom of its container, rather than holding its shape), it is, in the majority composed of fatty acids which are solids at room temperature (meeting the temperature based definition of Fats), and it's correct in the sense that oils are simply a special case of fats.
     
    Last edited: Jul 9, 2009
  11. Trippy ALEA IACTA EST Staff Member

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    10,890
    It occurs to me that my previous post might not be entirely clear.

    What I'm saying is this.

    Yes, Milk contains predominantly fats.
    Yes, Milk behaves like a liquid at room temperature.
    Yes, a Fat that is liquid at room temperature is correctly called an oil, not a fat.
    Yes, even when considering isomers of the same fatty acid, fats and oils have different physicochemical properties.

    However these facts are not neccessarily contradictory.

    And as far as the viscosity of non-newtonian fluids goes, that depends on the fluid being considered.

    According to Wikipedia, Blood Plasma is a pseudoplastic non newtonian fluid, it's viscosity decreases with increasing stress.

    It seems to me that cream fits the definition of a rheopectic non netonian fluid - it's viscosity increases the longer the stress is applied for, but, i'll try and have a look and see if I can find anything useful in my rheology notes (assuming I can find them).
     
  12. Betrayer0fHope MY COHERENCE! IT'S GOING AWAYY Registered Senior Member

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    2,311
    I was gonna suggest thissssssssssss. I am off to start a new thread.
     

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