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The Smell of Garlic and Enzymatic Oxidation

  1. Feb 28, 2015 #1

    We are working on project at school about garlic breath.Here is the article I have read in Popular Science magazine which gave me and idea.The article was about how to cure garlic breath and it gave some solutions about it.And I find these two(I copied them below from the original article) interesting and I have made some research online.I found out about the compound and enzyme in apples which make it turns brown when the surface of it touches with oxygen in the air. But I still need more information about to complete my project.So could someone please inform me about the this part of article? Thank you.

    **EAT AN APPLE **
    Fruits that brown when exposed to air contain an oxidating enzyme. This compound also sets off a chemical chain reaction that deodorizes offending sulfides.
    It’s loaded with plant chemicals known as polyphenols, which work through a similar mechanism to neutralize all four sulfide compounds.
  2. jcsd
  3. Mar 1, 2015 #2


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    You should google a bit.

    Here is some chemical/biochemical background, not very complete.
    Do not discouraged by the chemical terminology, that's all it is - terminology, to describe systematically those structures that are illustrated.
    Maybe you could try the effect of apple squashes or centrifugates on slices of garlic in a saucer, without having to chew it!


    One of the articles mentions alliin is racemic (mixture of two stereoisomers). But I remember only one of them smells. You can find out easily googling what stereoisomers and racemic mean. But all book examples will be for carbon, not for sulphur. Any question arising come back.
  4. Mar 1, 2015 #3
    Thank you for replying.But there is still a specific point I can´t understand.
    Basically,I can say we are working on a product that works against the garlic breath.I know that when allicin digested in human body it releases sulfide gas and it comes mouth from stomach and that is the main reason of garlic breath.
    And related to what I found online,I know that the plants include polyfenols,deactive the sulfur compounds in garlic.But how?I guess I need some equations for reactions.
  5. Mar 1, 2015 #4


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    OK your main focus should be experimental. Start next time you meet if possibile. If you do not find any effect there will not be so much to write about. If you do seem to find an effect do you know what a control experimental is?

    If you do find and effect, one extra experiment I would suggest is try the apple centrifugate after holding it at 100 degrees for a minute or so. That should inactivate most enzymes.

    You won't be able to deduce any chemistry from your experiments, so make it clear in your write-up this is just some interesting relevant information you have gathered. You don't have to write anything that goes so far beyond what you can readily be expected to understand at your stage that it's ridiculous - i.e. you can show off a bit but not too much. Not too much IMO is to know about enantiomerism (stereoisomerism) because you have to meet that sooner or later. And the fact for sulphur compounds like alliin is less well known than for carbon compounds, you may see in your textbook, and cute. To know or find out what cysteine is would not be showing off excessively.

    What the actual products of the enzyme reaction are I don't know, you may find out googling, or it is possible no one knows, sulfite I guess, or quite heterogeneous.

    You have probably experienced that sulphur chemistry is generally smelly. Sulphydryl compounds (with -SH) are the worst and you probably know one? You should realise that the smelliness of compounds depends on two things - intrinsic smelliness and volatility. For instance mercaptoethanol (HOCH2CH2OH) is in every biochemical lab in aqueous solution (to keep protein cysteine -SH reduced) and smells tolerable, almost healthy, but ethyl mercaptan (CH3CH2SH) is dreadful (used I think in warning systems). If available try and smell a bottle of cysteine and it might remind you of something depending on the life you've led. (The bottle may be cysteine, it may be the hydrochloride salt.) Then the vapour smell depends on how a compound binds to smell receptors in the nose, hardly predictable, maybe catalogued to some extent; I think fairly long carbon chains are the most potent. Finally realise that the smell of a compound is not always really of that compound but may be of minor impurities.

    Then about polyphenols I do not know, I was even surprised because rather than oxidising agents I thought of them as reducing agents and free radical traps. Quick Google showed their health-related effects are a big complex research area. I extracted these words of wisdom from an article:
    Lastly, we should not forget that many polyphenols have a taste and/or a color (29); food must be not only good for health but also acceptable to consumers.

    Re garlic my wife tells me if you take away the central 'nerve' from a clove it smells much less.

    Keep us informed of the experiments! :oldsmile:
  6. Mar 1, 2015 #5

    Thank you again for your reply.It really helped me especially the expirements you suggested about apples.And about polyphenols,I tried explained that the reaction happens when the apple´s surface turns brown is caused by a compound called tannen.Tannen( or tannic acid) make brown compounds called melanins when it react with oxygen.I have meant it at my previous threads,if I was not clear about it.And I have one more question,could you please retell me what the article meant saying "This compound also sets off a chemical chain reaction that deodorizes offending sulfides." So I can have a new perspective to search it differently.I might me asking same question over and over again,sorry for that.But I am really distracted about this sentence and it could be the main idea of my project. :)
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