Lemons are many things, and January is a good time to fill a bowl with half a dozen. Take one, dig your nail into its oily, open-pored skin, sniff and make a mental list. Lemons are also full of particles with a positive electric charge, which, when on the loose, are like teenage boys in a brand new electric car, cruising around looking for other molecules to attach to, and in doing so they change them. It is this concentrated proton activity that the nerves in the tongue and brain interpret and experience as the sensation of sourness when they encounter lemon.
We studied this at school, and also stuck copper wire in oval fruits with nipples in order to make a lemon battery. However, it was rereading Margaret Visser’s tart and witty chapter on lemons in her book Much Depends on Dinner that reminded me of the science; how the movement and proton pumps result in the formation of citric acid, which explains much. Lemons are not just handy, long-lasting, perfectly packaged, sunny, essential, beautiful and so on, they are charged, they are jump leads, they are a sort of edible electricity. No wonder we get such a thrill from a wayward spritz of juice that hits an eye, a twist or a slice.
January, particularly this January, is a good time to make spaghetti with lemon, parmesan and cream; a smooth and sharp dish that is also useful in that the sauce takes almost exactly the same amount of time to prepare as the pasta takes to cook.