What’s happening here as I melt the hard fats?

Discussion in 'Lye-Based Soap Forum' started by Mobjack Bay, Nov 9, 2019.

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  1. Nov 13, 2019 #21

    Millie

    Millie

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    @DeeAnna That helps a lot! It is easy to start over-thinking things and get confused, but I can pretty much understand anything that involves chocolate and cookies :)
     
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  2. Nov 13, 2019 #22

    TheGecko

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    Yes and no. I understand the analogy perfectly, but in giving the Red M&Ms the time to melt, aren't you running the risk of burning the cookie dough?

    You say Palm Oil is Palm Oil, not a mixture of random free fatty acids, yet aren't we supposed to pre-melt Palm Oil to make sure all the fatty acids are evenly distributed?

    When I made a beef stew, I don't add all the ingredients at the same time because if I did, the potatoes would be much by the time the carrots are fully cooked and the beef is tender. So I cook the beef and carrots first, then halfway though add the potatoes and then near the end, add the corn. So I've been treating my soap ingredients like beef stew...melting the Cocoa Butter about halfway, then adding Palm Oil, then Coconut Oil then using the residue heat to melt the Shea Butter...even though Shea Butter has the same Stearic content as Cocoa Butter, it takes a lot less time to melt it.

    So the confusion can be great...kind of like Common-Core Math vs Advanced Algebra.
     
  3. Nov 13, 2019 #23

    Mobjack Bay

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    Here's how I would describe what's happening. Someone please save me if I get it wrong :)

    The melting we're concerned with is the kind that transforms solid or semi-solid fats to liquids. In the fully liquid state, individual triacylglyceride (TAG) molecules are the dominant form. We don't want to heat to the point that we encourage the breakdown of the individual TAG molecules into glycerin and free fatty acids (or something else that makes the TAG or FA more prone to oxidation*). We do want to heat to just the point at which crystalline structures that contain multiple TAGs are eliminated (or very rare?).

    *actually, my understanding of what makes the TAG or FA molecules in PUFAs most susceptible to oxidation is weak. Is it just that a single bond is weaker than a double bond?

    ETA: I found this description of the process, here:
    "During the process of oxidative rancidity, oxygen molecules interact with the structure of the oil and damage its natural structure in a way that can change its odour, its taste, and its safety for consumption.

    Oxidation of fats, generally known as rancidity, is caused by a biochemical reaction between fats and oxygen. In this process the long-chain fatty acids are degraded and short-chain compounds are formed. One of the reaction products is butyric acid, which causes the typical rancid taste.

    Rancidification is the decomposition of fats, oils and other lipids by hydrolysis or oxidation, or both. Hydrolysis will split fatty acid chains away from the glycerol backbone in glycerides. These free fatty acids can then undergo further auto-oxidation. Oxidation primarily occurs with unsaturated fats by a free radical-mediated process. These chemical processes can generate highly reactive molecules in rancid foods and oils, which are responsible for producing unpleasant and noxious odours and flavours."

    If heat is one variable that might contribute to DOS with the more fragile oils and it's one I can control, it seems worth the effort to pay more attention to how I melt my fats. I just bought a heating pad that has a 110F setting and then another that is 135F. I'm curious to see if I can fully melt PO (visual confirmation) with gentle heat over a period of time that would normally test my patience.
     
    Last edited: Nov 13, 2019
  4. Nov 13, 2019 #24

    DeeAnna

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    No, because you're not melting just the M&Ms. You're "melting" the entire cookie as a molecular whole.

    edit: The melt temps of the different types of fat molecules in, say, palm oil is not all that large. The fat does not need to be overly hot to fully melt.

    If you want all the cookies with mostly red "stearic" M&Ms to be evenly mixed with other cookies that have fewer red M&Ms, then, yes, that is correct.

    If you melt palm oil and then allow it to cool, the palm oil molecules that contain more stearic acid will solidify first. This is the "stearin" portion of the fat. These stearin particles tend to settle to the bottom of the container if the oil cools slow enough.

    When the palm fully solidifies, the "olein" portion of the fat -- the fat molecules that contain more oleic acid -- will tend to be more at the top of the container. The stearin portion will tend to be more at the bottom.

    If you want a consistent mix of palm oil for soap making, scoop some palm from the top, middle, and bottom of the container when measuring the fat for a batch. Or melt the fat, stir well, and portion the melted fat into individual batch amounts. Or keep stirring the larger container of melted palm until all of the palm solidifies and then keep the homogenous fat from melting until it's time to use it.

    There is a difference in melt temp between olein and stearin, but this temp difference is much smaller than the difference in melt temps between oleic acid and stearic acid.
     
    Last edited: Nov 13, 2019
  5. Nov 14, 2019 #25

    TheGecko

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    This what I think I will do. I’ve been buying my PO from BB and it comes in 7lb bags and I typically make one and two pound batches of soap, so the PO gets reheated over and over again and I worry about it breaking down. So I have tried a few different things, but this last batch of soaps I didn’t get the PO well mixed in its semi-liquid state and I got steric spots in them. I have found a supplier for a ‘no-stir’ PO, but it’ll be January before I can give it try.

    Thank you very much for taking the time to explain things. Not quite sure if I understand 100%, but I’m getting there.
     
    Last edited: Nov 14, 2019
  6. Nov 14, 2019 #26

    DeeAnna

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    It sometimes takes me a few tries to explain things in a way that clicks with other people. It's fun to see the "light bulb" turn on in a person's eyes (or words) when I explain it right and the person can finally digest the information.
     
  7. Nov 14, 2019 #27

    TheGecko

    TheGecko

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    Was trying to edit, not repost. Sorry.
     
  8. Nov 14, 2019 #28

    TheGecko

    TheGecko

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    @DeeAnna

    Yeah, it sometimes takes me a few tries before I finally 'get' something.
     
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  9. Nov 17, 2019 #29

    Mobjack Bay

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    136F seems to be the sweet spot for fully melting the palm and Shea mix that I’m using. I haven’t tried melting them separately or done controlled time trials above 120F. So far, 120F for 10 minutes isn’t enough to get rid of the tiniest specks.
     
  10. Nov 23, 2019 #30

    Mobjack Bay

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    Today I worked with a tallow and lard shortening mix for the first time. I didn’t see the flaky looking dust-like particles that I’ve been seeing in my palm and Shea mix. Instead, once everything was melted (temp was 125 F) I noticed what looked like very fine black(!) particles in the liquid fats. This was using a magnifying glass :). I was sure there was some kind of contaminant in the fat, but then they slowly disappeared as I heated the mix to 135 F. Some were spherical, but many were not. The black appearance is puzzling. Maybe they were microbubbles or aggregations of microbubbles?

    The soap I made with the palm shea base has no stearic spots in the body of the soap, which is great, but I managed to get air bubbles instead. I know they’re bubbles because I get little holes when I plane them. I also ended up with a bit of ash on the top.

    A2873050-AE16-4B6B-9010-2257ECD89AF3.jpeg
     
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