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    Modified Palm Oil In Cheap Chocolate
    By Enrico Uva | April 25th 2011 12:37 PM | 4 comments | Print | E-mail | Track Comments
    About Enrico

    I majored in chemistry, worked briefly in the food industry and at Fisheries and Oceans. I then obtained a degree in education. Since then I have...

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    Most readers here are well-acquainted with trans fats and the classic Nurse's Study published in the New England Journal of Medicine. Most of the ensuing legislation that either banned or limited the content of trans fats in groceries was rooted in one of the  conclusions from that study:

    the replacement of 2 percent of energy from trans fat with energy from unhydrogenated, unsaturated fats would reduce risk of coronary heart disease by 53 percent (95 percent confidence interval, 34 to 67; P<0.001)
    It's also common knowledge that a portion of the food industry responded to the new limitations by turning to palm oil as a substitute. So-called palm oil is actually a solid at sub-tropical temperatures because it melts at
    33 to 39 oC. The reason for the melting point range is that palm oil like most triglycerides in food is not a single compound but a mixture of similar ones. But to create that trans-fat like texture the melting point is too high. So what's the solution?

    First a quick review of triglyceride chemistry. A triglyceride is basically an ester, formed in nature by the reaction of  fatty acids and glycerol. 

    Here is a general formula for a triglyceride, whose properties will vary depending on the alkyl groups (R1, R2 and R3: highlighted in red). The glycerol skeleton is highlighted in blue.

    The
    R1, R2 and R3 groups are basically fatty acids minus the -CO2 group that's already represented in the general structural formula. Here are three examples of fatty acids.



    Cocoa butter is a triglyceride obtained from the cocoa bean, and it is used to make chocolate. When mixed with the right ingredients, it's delicious. In addition, the fairly constant combination of fatty acids found in the beta form give this triglyceride another desirable property: a sharp melting point of 35 to 37
    oC, which coincides with the average range of human mouth temperatures. But cocoa butter is expensive, so in the past some of it was substituted with partially hydrogenated oils. Once anti-trans fat laws were passed, manufacturers of inexpensive chocolate could not simply use palm oil, whose melting point is not sharp enough. So what they did instead is rely on the interesterification of triglycerides, one of several methods of "modifying an oil". Eighty percent of cocoa butter triglycerides have palmitic and stearic acids in the Rand R3 positions with oleic acid in the R2 slot. To create an impostor molecule from palm oil, a stearic acid residue is introduced at the Rand R3 positions, where it's normally absent. 
    There are different ways of interesterifying. The superior method relies on enzymes because it leaves the
    R2 position unchanged. The catalyst that creates a greater hodge-podge of products is sodium methoxide. In either case, we don't exactly have the equivalent of a "Nurse's Study" to investigate the health impact of these molecules that are being included in foods.

    Look for modified palm oil in the average candy bar and especially in cheap Easter chocolate, where it is the second most common ingredient after sugar. It is also found in albeit smaller quantities(3 to 5%) in several versions of trans fat -free margarine.

    REFERENCES


    http://palmoil.com/useful_info/dd          Information about palm oil from the industry
    http://www.nejm.org/doi/full/10.1056/NEJM199711203372102   The Nurse's Study
    http://www.lsbu.ac.uk/biology/enztech/interester.html  More details on interesterification
    http://www.canada.com/topics/news/story.html?id=fd113bdf-6686-496a-8161-06a85546a1b8A General article on modified fats

    Comments

    UvaE
    Fractionated oils are less worrisome because they're formed by just using a physical separation method based on heating, cooling and filtration. Unlike hydrogenation, partial hydrogenation and interesterification, the heating, if gentle enough, does not create new compounds. JitKang Lim . a chemical enginner and senior lecturer, describes the industrial process used in Malaysia at: http://www.andrew.cmu.edu/user/jitkangl/Palm%20Oil/Refinery%20of%20Palm%... Just scroll down to the "Fractionation: Value added process?" section.
    rholley
    I’ve just had a look at Lim Jit Kang’s page on industrial processes.  I agree that fractionation sounds much the best process.

    If they’re distilling the fatty acids, does that mean that they are hydrolysing the oils first then re-esterifying them after distillation?  It sounds quite a destructive process, like over-frying plus.

    Hydrogenation – ’nuff said.

    I wonder – could the olein product be used for food and the stearin product de-hydrogenated for biodiesel?


    Picture from Wikimedia Commons.
    Robert H. Olley / Quondam Physics Department / University of Reading / England
    UvaE
    If they’re distilling the fatty acids, does that mean that they are hydrolysing the oils first then re-esterifying them after distillation? It sounds quite a destructive process, like over-frying plus.
    It sounds like it.
    I wonder – could the olein product be used for food and the stearin product de-hydrogenated for biodiesel?
    I don't know if the stearin product could be used for biodiesel, but in general, transesterification is used in making biofuels.
    if they’re distilling the fatty acids, does that mean that they are hydrolysing the oils first then re-esterifying them after distillation? It sounds quite a destructive process, like over-frying plus

    AFAIU the "[steam] distillation (SD) of fatty acids", as decribed in linked article, is just a part of REFINING the crude palm oil (CPO), and these fatty acids (FA) (as I understand from the description) are present in CPO as one of many naturally ocuring impurites. (As oppposed to FA produced deliberately by hydrolysis.)

    Steam distillation, AFAIK, can be used equally well for distillation/ fractionation of many hydrophobic substances (= non-miscible with water), including any fatty acids obtained for whatever purpose by hydrolysis of any trigliceride(s) - but in the process described in the article SD (vacuum variety) seems to be used only for purpose of purification (rafination) of CPO.

    About the "destructiveness" of steam distillation: SD itself IS NOT a destructive process (especially when compared to "overfrying") since it takes place at much lower temperatures than it would take to "normally" distill many organic compunds - in fact, SD is used for destillation of various oils (or fatty acids) - precisely for the reason it can prevent thermal destruction (decomposition) of said oils (where thermal decomposition, or "smoking point", often comes long before boiling point; see http://en.wikipedia.org/wiki/Steam_distillation for concise description of this process).

    Furthermore, in this particular instance (CPO rafination) the "high vacuum" variant of SD is employed, and that very low pressure reduces the temperature of SD even further.

    And if "hydrolysis" is that "destructive process" that you meant in your question, then YES, hydrolysis is, by definition, a very destructive -for TRIGLYCERIDES- process, yet reversible one.
    That is, during hydrolysis triglicerides are intentionally "broken" ("cracked") into its main "base compounds" (glycerine and fatty acid), but the fatty acids themselves are not damaged (at least not to significant degree), unlike it is the case with thermal decomposition of oils (or any other fats, or triglycerides).
    So hydrolysis is not "like overfrying +" - it is simply a case of "breaking" an ester (triglycerides are esters) at its weakest point, without damage done to molecules of either alkohol or (fatty) acid.

    Hope it clarifies the matter a bit... ;-)

    Best,
    K. Wozniak