Compound Interest: Why Can Coriander Taste Soapy?

I wasn’t aware of this until recently, being a fan of coriander myself, but apparently there are quite a few people for whom coriander (referred to as cilantro in the US) has a rather unpleasant soapy, or even metallic, taste. The cause of this has its roots in the chemical composition of coriander leaves – though, as I discovered, there are also other factors at play.

The chemical composition of the essential oil of coriander leaves has shown it to be composed of around 40 different organic compounds, with 82% of these being aldehydes, and 17% alcohols. The aldehydes are mainly those with 9-10 carbon atoms, and it is these that are largely responsible for the aroma of coriander leaves – as well as its perceived soapy taste for some people.

The aldehydes present in coriander, as well as those similar to them, are also commonly found in both soaps and lotions. Interestingly, some are also amongst the compounds excreted by stink bugs when they are disturbed. Given that, perhaps it’s not completely surprising that, for some people, the smell and taste of coriander is a little on the repulsive side.

However, it’s certainly not just down to the chemical composition of coriander leaves that some find it has a soapy taste, whilst others do not. It’s been suggested that there’s also a genetic basis to this, which explains why not everyone has the same aversion. Scientists have highlighted a specific gene that codes for a receptor that is highly sensitive to the flavour of aldehydes. Several other genes have also been linked, however, so it seems likely that more than one could be responsible.

As well as this, it’s also possible for people to grow to like the taste of coriander, with it being suggested that repeated exposure to the taste leads to the brain forging new, positive associations. The strength of the aldehydes’ effect on the taste of coriander can also be mitigated by crushing the leaves before consumption, with studies having shown that this speeds up the rate at which the aldehydes in the leaves are broken down by enzymes.

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