Odiferosity
Maastrictian asked last night why rubbing stainless steel over a chopping board removes the odour of garlic.
The short answer is: I don’t really know, but then again, neither do any of experts I consulted. Nonetheless, with the aid of Harold McGee, the interweb, and lessons beaten into me by my middle school chemistry teacher, I have a long answer for you.
To begin with, McGee notes that acid ingredients, like vinegar and lemon juice, are traditionally used to mask the flavour of less than perfect fish because the free hydrogen bonds with the noxious compounds in fish. This process doesn’t actually neutralize their smell, but it does cause the offending molecules to become positively rather than negatively charged, which makes it easier for them to bond with water and other molecules, essentially gluing the odious bits down.
Knowing that rubbing your hands with a lump of stainless steel also helps remove the fishy odour, the suspicion must be that a similar process, based on static electricity, is at work. It’s entirely possible that a similar chemical reaction is actually taking place, but I couldn’t easily find enough information about the molecular structure of stainless steel to say.
This shows the chemical structure of the molecule responsible for the distinctive garlic smell. Someone who knows more than I do about chemistry should be able to figure out whether everything I’ve just written about fish will apply to garlic.
August 30th, 2005 at 1452
Hmmmmm, I’m not sure I buy it. Which does not mean I have a better explaination
Fish odor is nitrogen based while garlic odor is sulfide based. Further, while lemon, an acid, seems to work on garlic smell acording to Google, so does baking soda, a base. So the analogy to fish odor doesn’t make sense (to me)
This article suggests that the metals in stainless steel are reacting with the sulfer in garlic odor to form inert compounds. But this doesn’t really make sense.
Stainless steel is stainless because it has a high chromium content. When exposed to oxygen the chromium on the surface of the blade forms a thin layer of chromium oxide. This prevents further oxygen from getting to the iron, oxydizing it and causing it to rust. We might suppose that oxygen is displaced by sulpher, but this doesn’t seem to happen. The CrO bond is stronger than the CrS bond.
Which doesn’t bring me any closer to the truth, of course
–Chris
August 30th, 2005 at 2030
I actually saw the chemistry.about.com article you linked, and similarly dismissed it as not making sense.
Can you put your finger on why you don’t think electrical charge has anything to do with it? I’m just not sure how else stainless steel would be able to affect odour molecules.
September 6th, 2005 at 0031
Chris is right in dismissing the claims - the (pretty much) inert surface of stainless
steel preludes the possibility of chemical displacement. [Aside: Are you sure that’s
what McGee wrote? I thought the volatile components in acids combined with the noxious
fishy compounds]
I’m not sure about static electricity playing a role, but then again I’m no scientist.
September 12th, 2005 at 0343
That is a very nice picture of garlic. Did you take it yourself?
All I can say about garlic is, usually, the more the merrier.
October 12th, 2005 at 2123
Ah, garlic, no matter the chemistry it is one of my favorite ingredients in cooking… We eat garlic virtually every day and still no vampires, guess it works!