For a minority of people coriander leaf tastes of soap. The leaf is rich in aldehydes also used in soaps, and a genetic variant near the smell receptor gene OR6A2 is linked to disliking it.
The short answer¶
Coriander leaf — called cilantro in the Americas — owes much of its smell to a group of aldehydes, particularly long-chain unsaturated ones such as (E)-2-decenal and (E)-2-dodecenal, together with decanal. Similar aldehydes are used in perfumes, soaps and lotions, and some occur in the defensive secretions of insects. Most people perceive the blend as fresh, green and citrusy. A minority perceive it as soapy, metallic or foul.
Genetics explains part of the difference. A variant in a cluster of olfactory receptor genes on chromosome 11, near a gene called OR6A2, is associated with finding coriander soapy.
The genetic evidence¶
🔬 OR6A2
In 2012 researchers at the genetics company 23andMe published a genome-wide association study of tens of thousands of customers who had answered questions about coriander. The strongest signal was a single-letter variant (SNP) in a cluster of olfactory receptor genes. One of them, OR6A2, codes for a receptor known to respond strongly to aldehydes of the kind found in coriander leaf, making it the most plausible candidate. People carrying two copies of the associated variant were more likely to report a soapy taste.
The effect is real but modest. The variant accounts for only a small share of the variation in how people feel about coriander, and many people without it dislike the herb while many with it do not. Twin studies also suggest a genetic contribution, but experience, exposure and culture clearly matter too.
How common is the aversion?¶
Estimates vary with the population and how the question is asked. A 2012 Canadian survey of young adults found dislike ranged from a few per cent among people of South Asian, Hispanic and Middle Eastern ancestry to around a fifth among people of East Asian ancestry, with people of European ancestry in between. That pattern fits the idea that growing up eating a herb makes it familiar, although genetic differences between populations may play a part. Figures around 10–20% are often quoted for Europeans and North Americans, and should be taken as rough.
Seed versus leaf¶
Coriander seed is an entirely different flavour. Its essential oil is dominated by linalool, a floral, orangey terpene, and it contains little of the leaf's aldehydes (see aroma-compounds). Many people who cannot bear the leaf are happy with the seed in garam-masala or pickling spice.
Can the soapiness be reduced?¶
Aldehydes are reactive, and there are anecdotal and some experimental reasons to think that crushing the leaves — as in a pesto, chutney or zhoug — speeds their breakdown by the plant's own enzymes, making the paste less soapy after it stands for a while. Heat also drives the lightest aldehydes off, which is why coriander cooked into a curry is less divisive than raw leaves scattered on top. Neither fix works for everyone.
🔁 Coriander-free alternatives
For those who find coriander soapy, flat-leaf parsley gives a similar green freshness without the aldehydes. mint, thai-basil or a little dill can stand in, depending on the dish. culantro and vietnamese-coriander contain similar aldehydes and are unlikely to help.
Where the herb is loved¶
Coriander leaf is among the most widely used fresh herbs in the world, central to mexican-cuisine, thai-cuisine, vietnamese-cuisine, indian-cuisine and much of the Middle East, from salsas and green-chutney to chermoula and zhoug. For cooks feeding a mixed crowd, serving it on the side is the diplomatic answer.
Etymology¶
The name comes via Latin coriandrum from Greek koriannon. It is often said to derive from koris, "bedbug", on account of the smell of the unripe plant; the link is plausible but not certain. See etymology-of-spice-names.