Pongy Ponderings

This is a bit of a cheat, but here is an article I wrote for my college magazine (following "Going Bananas"). I thought it was about time I added to my oeuvre and posted it up here. Enjoy!

Commissioned once again by our illustrious editor to get my geek on and bring more pithy and zesty morsels (see what I did there?) of culinary science to the discerning readers of Linacre, I happily agreed, confident that my ability to bulls**t about things I really know nothing of had not deserted me or been used up on my extended essay. However, later contemplation served to instil a deep and very real fear, nay, panic. Writer’s block! How to top the giddy heights of last term’s column, for which I had received such compliments as “I like bananas,” and “I saw your name- I’ll read it later?” What subject could possibly provide as much entertainment and pure comedy as the banana, that funniest of foods; comic trope and device recognised internationally as truly hilarious? The answer, I realised, with a sinking feeling in my stomach, is nothing. So, like the inferior second season of a once- sparkling sitcom, clearly acknowledging that I have peaked but desperately clinging to one last shot in a ratings war which I will surely lose, I am opting for the easy way out: gross-out humour. The last resort of the desperate comedian. There is no dignity in this, but, as our aforementioned illustrious editor has pointed out, my sense of humour is akin to that found in a 12 year old boy, so I know that I am not above this task. Therefore, the subject of this lacklustre, trying-too-hard and probably not even remotely interesting (it’s page-filler, basically) article is the science of smelly food.

Improbable as it may seem, there are actually quite a number of scientists who trouble themselves professionally with this, delving into their compost bins and furking about in the bottom of the fridge (well, I imagine it’s actually a bit more sophisticated than that, but you get my drift) to find out what the molecular source of the pongs and whiffs therein actually is. Onions and garlic are extremely popular amongst sulfur chemists, although I imagine not with their significant others, as the cause of their odour is a family of sulfur-containing compounds which are modified during cooking to alter the smell from eye-wateringly offensive to mouth-wateringly appetising. In the 1980s, scientists found that the compound in raw onions with which this odorous journey begins is an amino acid derivative called propenyl cysteine sulfoxide. Slicing the onion exposes this unfortunate chemical to an enzyme called alliinase, which breaks it down into propenesulfenic acid and the mayhem begins. Two molecules of propenesulfenic acid can combine to produce thiosulfinate which is responsible for that pungent raw onion smell, whilst cooking produces the taste bud-tingling aroma of bispropenyl disulfide. (On a side note, it is very pleasing to meet a pleasant-smelling sulfur compound. I am currently working with carbon disulfide and as such am the least popular chemist in my lab. **Sob** I can only imagine what the guys who work on this onion and garlic business go through. They must be even less popular than the physicists.)

So, that’s the vegetables, but what about the smelly proteins? Meat, fish and eggs all suffer from their own personal hygiene issues, as it were. In the case of eggs, the culprit is once again sulfur, in the form of hydrogen sulfide (H₂S), and this is not only found in rotten eggs. According to eHow (yes, my research methods are once again exemplary), boiling eggs the wrong way can also cause a pongy problem. Overcooking produces excess hydrogen sulfide, which reacts with iron in the egg yolk. This is the cause of the smell and also of the greenish colour that rings the egg yolk of an imperfectly hard-boiled egg. Good to know. On another side note, typing “rotten egg smell” into Google turned up this rather wonderful gem from The Independent: “How the smell of rotten eggs makes men randy.”  That’s right. Apparently, tiny quantities of hydrogen sulfide are released in penile nerve cells and may stimulate an erection, which could present an alternative treatment route for people suffering from erectile dysfunction who don’t respond to Viagra. I’ll let you form your own opinions about this, but if you are, by any chance, interested a) don’t tell anyone- they may make certain assumptions and b) look the paper up- it’s been published in PNAS (that’s the Proceedings of the National Academy of Sciences).

Well, that was quite a detour, so back to the original point. At this juncture we wish sulfur farewell, as there are other molecular offenders who deserve a little mention in this missive. The chemicals responsible for the stomach-turning smell of rotten meat and fish and pungent cheese are, in fact, nitrogen-containing. Fish flesh contains a compound called trimethylamine oxide, which is broken down upon decomposition to give nasty smelling tri- and dimethylamine, making it very easy to tell whether the fishmonger was lying or not when he told you that the fish you bought was freshly caught 3 hours ago, but very difficult to make your fridge smell nice again. Likewise, the nitrogen-containing molecule present in rotting flesh of the meat variety is aptly (but disturbingly) named cadaverine and is a diamine produced upon the breakdown of the amino acid lysine. And we have all experienced the gag-inducing whiff of ammonia (NH₃) emanating from a somewhat over-ripe wheel of brie. I am not only beginning to feel very sorry for the sad reputation sulfur has despite nitrogen’s equal culpability in this field, but also praying to the chemistry gods (or my supervisor) that I don’t have to start working with amines any time soon.

So there we have it, dear reader. Apologies if you began reading this column over breakfast (particularly if that breakfast contained fish or eggs). I hope that, in such a case, you can forgive me for this woeful attempt at a follow-up on the glory days of Hilary term and take comfort in the fact that you will be beginning your day marginally better informed on a subject with no practical use whatsoever. That’s kind of how I feel about my PhD…