Going Bananas

Yikes- it has been over a year since I last wrote anything on here, but recently, I was asked to write an article for my college magazine and (although Linacre Lines) had first publishing rights, I thought I'd whack it on here for those of you who don't have access to that high-brow and high impact publication.

We’re all used to a bit of geekery in Oxford. For most of us, reading around our subject isn't just a matter of making sure that our research sounds extremely relevant and important to a funding body, but an actual pleasure. Maybe I exaggerate, but I'm basically asking for your forgiveness and understanding as I get WAY too into a topic very tenuously linked to my subject for my own good. And for pretending that food can be an academic subject. Although I'm not the first person to have done that- there’s actually a guy who calls himself a Molecular Gastronomist. His name is Hervé This and he is really a physical chemist who likes to play with food. Sometimes he succeeds in making it dreadfully boring (“Algae contains fibres whose nutritional value is comparable to that of vegetable fibres.” Yawn!), but other times, he comes up trumps and gives some great tips on how to make a soufflé rise, or indulges me in my gluttony with pieces entitled “In Praise of Fats.” Amen to that! So I decided to take up his mantle and try to find and impart some (possibly a little bit) fun, scientific food facts, which satisfy the chemist in me and are mildly entertaining to most people who take an interest in what they put in their mouth.

For a good while now, I have been cataloguing a list of intriguing facts about bananas (I did ask for your forgiveness and understanding). This all started with the wonderful myth that an Oxford interview candidate was once asked to tell their interviewer about a banana. I sincerely doubt that this was the case, but began to ponder what on earth my response to such a question would be. I presume that in a Chemistry interview, some level of scientific detail would be required, so instead of describing majestic curvature and optimistic shades of yellow, I set about some taxonomy, inorganic chemistry and a touch of biochemistry.

My first revelation on my magical journey to understand this mystical fruit was that the banana ‘tree’ is actually… a herb. This nugget of knowledge was received with much scepticism by my friends (“Yeah, yeah Becky, next you’ll be telling me that a strawberry is actually a fish”) but a triumphant Google search- I didn’t say that this would be well researched!- revealed that I was, in fact, correct. The banana plant is of the herbaceous genus Musa, with the fruit we eat coming from the species Musa acuminata and Musa balbisiana. The herbaceousness of the banana is due to its trunk being comprised of leaves, rather than of woody matter. Who would have thought?  So, with those facts under my belt, maybe the Plant Sciences department would have me (possibly Classics, too, because of the Latin). But what about the Chemistry?

Doubtless many of you know that bananas are extremely rich in potassium. Possibly fewer of you know that this renders them a tad radioactive. An isotope (that is, a version of an element with the same number of protons but different number of neutrons) of potassium-40 (⁴⁰K) is radioactive, as it decays to calcium-40 via emission of an electron or to argon-40 via the emission of a gamma ray and a neutrino. Sounds quite scary, doesn’t it? But don’t worry, the amount of the radioactive potassium in each banana is very low, about 0.045mg, which equates to 0.1μSv radiation, so eating one a day isn’t going to cause you much damage. Some jokers at a U.S. think tank came up with the idea of the “Banana Equivalent Dose” to gauge the levels of radiation emitted by more strongly radioactive items. I’m not sure how useful it is to know that you absorb the same amount of radiation from a chest X-ray as you would from eating two hundred bananas, but I feel strangely reassured. Excellent. Chemistry covered.

Now, finally, the biochemistry. Have you ever seen those banana hooks? The ones you are meant to hang your bananas on instead of just chucking them into the bottom of the fruit bowl. Well, it turns out that they are not for purely aesthetic reasons, which is, I am sure, why people buy them. If this was an Art History interview and I were waxing lyrical about sunny hues and crooked forms, then I know that those hooks would be instrumental in my answer. As it is, they can also play a part in my scientific missive. Putting bananas in the fruit bowl is a bad idea. Fruits give off ethylene gas, which is a very simple organic molecule and a plant ripening hormone.  In the fruit bowl, the concentration of this gas in the atmosphere surrounding the fruit is high, causing the bananas and other fruit to ripen quickly and resulting in acute sadness when you find that your recently wonderfully yellow and firm fruit is now a squishy brown mess and devastatingly inedible. Unless that’s how you like your bananas, in which case throw them into the fruit bowl at your heart’s content.

So there we are. The next time you are being interviewed and the subject of bananas comes up, you too will be able to bore the pants off your prospective future employer and compromise your future to boot!