Unpleasant smells, the coronavirus, and corked wine

By now, I think it is quite well known that loss of sense of smell, or anosmia, is a key symptom of COVID-19, but this BBC News article explains how a short-term anosmia due to COVID-19 can turn into a longer-term parosmia, which is a distorted sense of smell. The parosmia seems to make many everyday substances, food for example, smell disgusting. I find this interesting, and not a little scary. I am not sure what the sufferers think, but given a choice between no smell and disgusting smells I think I would choose the former.

But to return to what I found interesting, when reading the BBC article I immediately thought of the disgusting smell of corked wine, which is primarily caused by the chemical 2,4,6-trichloroanisole, commonly abbreviated to TCA. Based on experience of corked wine you might think that TCA had two effects: one being to stimulate some smell receptor cells, to create a nasty smell; and the other to inhibit other smell receptor cells, to give the “fruit scalping”. However, experiments with newts showed only the inhibiting effect, and no receptor cell stimulation. We have to be a bit careful here, because of course the newt olfactory system might not behave like the human one but, on the face of it, the absence of any stimulation to create the corky smell seems rather puzzling. If the human nose behaved like the newt’s then could that mean that corkiness exists as a component of all wines, only to be revealed when other smells are suppressed? It seems unlikely, especially considering that other TCA-contaminated food and drink has the same musty smell.

Perhaps you can now see where this discussion is heading, and I must warn you that from this point it is all speculation on my part. It is possible there is a more solid basis in science, but I am not aware of one.

Could the COVID-19 parosmia be caused by some smell receptor types being inhibited, while others have been restored to a working state? And is that also the way that TCA gives rise to a musty smell, with some receptors types working and some inhibited? Note that in both cases it is not actually a case of aromas being removed from a blend, as there is not a one-to-one relationship between receptor types and aromas. Rather than aromas being removed, it is the taking out of action of receptor types, and that changes the shape of the “smell images” on the olfactory bulb, turning them into ones that are more similar to the images of bad smells (see my earlier post for a discussion of smell images). In the case of TCA, the smell that is distorted into mustiness could perhaps have nothing to do with the wine, but be the unnoticed background smell we have all the time from our own body (i.e. mouth, throat and stomach).

Speculation aside, I think you will agree that our sense of smell is an amazing thing, and of great value. Let’s hope that all COVID-19 sufferers manage to fully regain theirs. And may their wine never be corked.

Author: Steve Slatcher

Wine enthusiast

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