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Thread: Why does milk thicken when whipped?

  1. #21
    Quote Originally Posted by Asguard View Post
    ARE NOT FATS!!!!!!!!!!!!!11

    they are all LIPIDS yes but they are NOT fats, they are OILS!!!!!!!!!!. God you people really need to pick up a dictionary once in a while
    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:
    Fat
    ...
    –noun
    16. any of several white or yellowish greasy substances, forming the chief part of adipose tissue of animals and also occurring in plants, that when pure are colorless, odorless, and tasteless and are either solid or liquid esters of glycerol with fatty acids; fats are insoluble in water or cold alcohol but soluble in ether, chloroform, or benzene: used in the manufacture of soap, paints, and other protective coatings and in cooking.
    ]Fat
    Definition:

    Fats are organic compounds that are made up of carbon, hydrogen, and oxygen; they are the most concentrated source of energy in foods. Fats belong to a group of substances called lipids. Fats come in liquid or solid form. All fats are combinations of saturated and unsaturated fatty acids. Fats can be called very saturated or very unsaturated depending on their proportions.
    In contrast to solid fats, oils are fats that are liquid at room temperature, like the vegetable oils used in cooking. Oils come from many different plants and from fish. Some common oils:
    Because of the kinks in the hydrocarbon tails, unsaturated fats can’t pack as closely together, making them liquid at room temperature.
    You were saying?

  2. #22
    http://wiki.answers.com/Q/What_are_t..._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

  3. #23
    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:
    Fats may be either solid or liquid at normal room temperature, depending on their structure and composition. Although the words "oils", "fats", and "lipids" are all used to refer to fats, "oils" is usually used to refer to fats that are liquids at normal room temperature, while "fats" is usually used to refer to fats that are solids at normal room temperature. "Lipids" is used to refer to both liquid and solid fats, along with other related substances.
    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.

  4. #24
    I'm just going for a walk... ElectricFetus's Avatar
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    16,983
    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.

  5. #25
    Quote Originally Posted by Asguard View Post
    ARE NOT FATS!!!!!!!!!!!!!11

    they are all LIPIDS yes but they are NOT fats, they are OILS!!!!!!!!!!. God you people really need to pick up a dictionary once in a while
    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!!!!!

  6. #26
    Let us not launch the boat ... Tiassa's Avatar
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    30,521

    Cool 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.

  7. #27
    ALEA IACTA EST Trippy's Avatar
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    9,956
    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 by Trippy; 07-08-09 at 11:17 PM.

  8. #28
    ALEA IACTA EST Trippy's Avatar
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    9,956
    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).

  9. #29
    MY COHERENCE! IT'S GOING AWAYY Betrayer0fHope's Avatar
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    Quote Originally Posted by D H View Post
    Cream is a colloidal suspension of milk fats and proteins in a salty water solution. It acts like a fluid, more or less. (It is a non-Newtonian fluid.) Whipped cream is a foam and incorporates liquid, gas, and solids. It is very much a non-Newtonian fluid.

    Since you didn't like my last link, try this one: http://science.nasa.gov/headlines/y2003/09jun_foam.htm.
    I was gonna suggest thissssssssssss. I am off to start a new thread.

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