fresh cilantro

Fresh coriander leaf, Coriandrum sativum, which two recipes in this library add at different moments. Harrak osbao takes 30 grams, fresh or frozen and chopped, cooked with the crushed garlic for about 30 seconds, just until fragrant, early enough to perfume the pot from the base up. The Palestinian molokhiya with chicken takes a cup, finely chopped, in the taqliya, a sizzle of garlic, green chili and cilantro in olive oil poured in near the end: the chili for a few seconds, then the cilantro until it wilts and darkens, in a 50-second step. Both recipes name the aldehyde (E)-2-decenal behind its green, citrus-soapy scent.

The Journal's note on the cilantro gene says the chemistry is not in dispute: the leaf is mostly aldehydes. Across four cultivars, (E)-2-decenal ran from 15.7 to 25.1 per cent of the essential oil and decanal from 14.4 to 18.8 per cent. The soap comparison is weaker than it sounds. The note traces it to a 2010 New York Times column by Harold McGee, which said the same or similar aldehydes are also found in soaps, and observes that nobody appears to have measured a bar of soap for them.

The gene story is smaller than the meme. A 2012 study of 14,604 people found one variant beside a cluster of eight olfactory receptor genes; it explains about 0.5 per cent of the variance in calling cilantro soapy, and South Asian participants, whose cooking uses it by the bunch, were the least likely group to call it soapy, with an odds ratio of 0.270 against Europeans. In a 2010 study, cut leaves held in boiling water for two minutes lost aldehydes and gained alcohols. On whether repeated exposure trains the dislike away, the note finds no study at all.