Coriander

• 1. Introduction

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  Coriander, known to botanists as Coriandrum sativum, is an annual herb in the family Apiaceae, and it splits dinner tables in two. For most people, a fresh leaf tastes bright, with a faint citrus edge. For others, the very same leaf tastes like soap, or like something that has gone off. Nobody is imagining it. The disagreement is real, measurable and, as it turns out, partly written into the genes. That raises a string of questions. Why does one plant produce such opposite reactions? Where did it first grow, and who first put it on a plate? How did a kitchen herb end up with such an odd name? And how did its leaves, seeds and roots come to flavour everything from curry to gin?

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• 2. A Divided Palate

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  Surveys of dislike show 21% of East Asians turning against coriander, along with 17% of Caucasians and 14% of people of African descent. The pattern flips where the herb is a kitchen staple. Only 7% of South Asians, 4% of Hispanics and 3% of Middle Eastern subjects said they disliked it. Fans describe a refreshing, lemony or lime-like leaf. Detractors react to a pungent smell and taste that they call rotten. Twins offer the strongest clue. About 80% of identical twins shared the same verdict on the herb, while fraternal twins agreed only about half the time. A genetic survey of nearly 30,000 people then turned up two variants linked to how coriander is perceived. The more common one sits in OR6A2, a gene within a cluster of olfactory-receptor genes. It encodes a receptor that is highly sensitive to aldehyde chemicals. Flavour chemists found that coriander's aroma comes from about half a dozen substances, mostly aldehydes. People who dislike it are sensitive to the unsaturated aldehydes, and they may also fail to detect the pleasant aromatic chemicals that other people enjoy. Links to several further genes, including one for a bitter-taste receptor, have also been reported. Among the many compounds in the plant's essential oil, linalool is the major one, and it carries much of the herb's aroma and flavour.

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• 3. A Bed Bug Name

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  The word coriander first appeared in English writing in the late 14th century. It came from the Old French coriandre, which came from the Latin coriandrum. The Latin borrowed in turn from the Ancient Greek koríandron, which also appears as koríannon. That Greek word may be related to kóris, the Greek word for a bed bug. The likely reason is the plant's fetid, bug-like smell. The oldest written form is Mycenaean Greek. It appears in the Linear B syllabic script as ko-ri-ja-da-na, with spelling variants such as ko-ri-a2-da-na, ko-ri-ja-do-no and ko-ri-jo-da-na. Scholars reconstruct it as koriadnon, a form that resembles the name of Ariadne, the daughter of Minos. Spanish speakers use cilantro, a word that also descends from coriandrum. Because Mexican cooking leans so heavily on the fresh leaves, American English uses cilantro for them, yet the dried seeds still keep the name coriander.

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• 4. Oldest Traces

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  Fifteen desiccated mericarps, the dry fruit halves of the plant, were found in the Nahal Hemar Cave in Israel. They came from the Pre-Pottery Neolithic B level, which dates to six to eight thousand years ago. Another eleven came from Atlit-Yam, from roughly 8,000 to 7,500 years ago. If those finds truly belong to their layers, they are the oldest coriander found anywhere. The herb's native range is hard to pin down. It grows wild across a wide stretch of Western Asia and Southern Europe, so wild plants cannot easily be told from recent escapes. Recent work suggests that wild coriander in Israel and Portugal may be an ancestor of the cultivated crop. Those wild plants germinate poorly and stay small, and the Israeli fruit has an extremely hard coat. The Torah uses coriander as a point of comparison for the taste of manna, which implies that ancient Israelites knew it well. About 500 ml of mericarps were recovered from the tomb of Tutankhamen. Coriander does not grow wild in Egypt, so this may show that the ancient Egyptians cultivated it. The Ebers Papyrus, an Egyptian text from around 1550 BCE, also mentions uses of the plant. In Greece, cultivation may reach back to at least the second millennium BCE. A Linear B tablet from Pylos records the plant being grown for making perfumes, and it was used both as a seed spice and as a leaf herb. Large quantities from an Early Bronze Age layer at Sitagroi in Macedonia could point to even earlier cultivation. Written praise followed, with Hippocrates mentioning coriander around 400 BCE and Dioscorides doing so in 65 CE.

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• 5. Umbels and Lookalikes

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  Standing up to 50 cm tall, the coriander plant is soft rather than woody. Its leaves change shape as you climb the plant. Near the base they are broadly lobed, but on the flowering stems they turn slender and feathery. The flowers gather in small umbels, in white or very pale pink. Each flower is asymmetrical, because the petals pointing away from the centre of the umbel grow longer than those pointing inward. The fruit is a globular, dry schizocarp, and the pollen grains measure approximately 30 μm. Several other plants borrow the herb's name or its flavour. Eryngium foetidum belongs to the same family, Apiaceae, and tastes similar but more intense. It goes by culantro and ngò gai, and it turns up in the cooking of Mexico, the Caribbean, Central and South America and Southeast Asia. Persicaria odorata, called Vietnamese coriander or rau răm, has leaves with a similar smell and taste. It is no relative, since it belongs to the Polygonaceae, the buckwheat family. A third impostor, Porophyllum ruderale subsp. macrocephalum, is sold as summer cilantro. It belongs to the sunflower family, Asteraceae, and grows wild from Texas to Argentina.

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• 6. Leaves and Roots

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  Chutneys, salads, salsa and guacamole all lean on fresh coriander leaves, which also garnish soup, fish and meat. English speakers call them coriander leaves, fresh coriander or Chinese parsley. Heat dulls their flavour, so cooks usually serve them raw or stir them in just before the dish reaches the table. Indian and Central Asian recipes break that habit. There the leaves, called dhania, go in by the generous handful and are cooked until their flavour fades. Handling is awkward, because the leaves spoil quickly once cut from the plant. They also lose their aroma when dried or frozen. The leaves and the seeds taste different from each other. In the leaves, the dominant flavour compounds are the aldehydes 2-decenal and 2-dodecenal. Below ground, the roots carry a deeper and more intense flavour than the leaves. Thai cooks use them in soups and in curry pastes, and other Asian cuisines use them too.

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• 7. Seeds and Spirits

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  Crush a coriander seed and a lemony citrus flavour is released. Linalool makes up about two thirds of the seed's volatile components, and pinene supplies much of the rest. Cooks describe the result as warm, nutty, spicy and orange-flavoured. The seeds are really the plant's dry fruits, and in a recipe the word coriander may mean only them. Varieties differ. The type C. sativum var. sativum, the type var. microcarpum with fruits of 1.5-3 mm, and var. indicum with its elongated fruits all produce different seeds. Large-fruited kinds grow mainly in tropical and subtropical countries such as Morocco, India and Australia. They hold little volatile oil, 0.1-0.4%, so they go to the spice trade for grinding and blending. Small-fruited kinds come from temperate regions and hold 0.4-1.8% oil. That makes them a prized raw material for essential oil. Roasting the seeds in a dry pan heightens flavour, aroma and pungency. Ground seed fades fast in storage, so it is best ground fresh. Garam masala includes coriander seed. Indian curries often use the ground fruits in quantity alongside cumin, where they thicken the sauce in a mixture called dhania jeera. Roasted seeds, called dhania dal, are eaten as a snack. Outside Asia, the seeds go into vegetable pickles. German and South African cooks add them to sausages, including boerewors. In Russia and Central Europe, they sometimes stand in for caraway in rye bread such as Borodinsky. The Zuni people of North America grind the seeds with chili peppers into a condiment for meat, and they eat the leaves as a salad. Some Belgian wheat beers are brewed with coriander seeds and orange peel for a citrus note. The seeds are also among the key botanicals that flavour gin. One further claim lists coriander among the original ingredients in the secret formula for Coca-Cola.

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• 8. Nutrition and Allergy

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  Raw coriander leaves are 92% water, 4% carbohydrates, 2% protein and less than 1% fat. Per 100 g, the leaves are especially rich in vitamins A, C and K, and they hold moderate amounts of dietary minerals. The seeds have a different profile. They carry fewer vitamins but supply significant dietary fibre, calcium, selenium, iron, magnesium and manganese. For some people, the herb is a hazard rather than a nutrient. A cross-sectional study examined 589 cases in which food allergies to spices were suspected. Pin-prick tests were positive for coriander and its Apiaceae relatives, including caraway, fennel and celery, in 32% of children and 23% of adults. Symptoms resemble those of other food allergies, and they can be minor or life-threatening. A preliminary study also found that coriander essential oil inhibited both Gram-positive and Gram-negative bacteria. The list included Staphylococcus aureus, Enterococcus faecalis, Pseudomonas aeruginosa and Escherichia coli.

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