The taste is quite pungent, hot and bitter, and they are usually roasted - either dry or in a little ghee which tones them down a bit.
The plant probably originated in Egypt, maybe India, is now grown all over the Middle East and India. It is a very old plant and, like many herbs a spices, was used medicinally for centuries. For some strange reason this seems to be a spice which has never quite made it in the West and seems to be used principally in Indian and other Eastern cuisines
Carom seeds have a strong flavour which can overpower everything else so they are used principally as a condiment rather than as a main element of a spice mix. They can be roasted and added to a dish like garam masala but beware, even a small quantity will make themselves known. Tadka or chhaunk is where you put some whole spices in a little oil or ghee, fry for a few seconds and use this as a garnish. Ajwain is a common ingredient in this along with cumin seeds and black mustard seeds.
I sometimes to use a few carom seeds in naan bread (mix in with the flour before adding the liquid) and also for making snacks like Namak Paare
The spice has good digestive qualities and so is good with vegetable dishes and particularly lentils where they help lessen the flatulent effects of the lentils. Other starchy snacks like aloo chaat, potato balls and bombay mix benefit from a little ajwain as it both gives it a kick and helps with digestion.
Carom seeds are eaten in such small quantities that it seems a little strange to consider the nutritional benefits, however, for the record, they are rich in calcium, phosphorus and iron.
The medicinal features are of much more interest. The essential oil in carom seeds is about 50% thymol; this is a powerful antibacterial, germicide, fungicide and anti-spasmodic. Thymol is actually used commercially in toothpastes and perfumes.
In India, ajwain is routinely used as a remedy for indigestion, diarrhea, colic and other intestinal problems; although this has probably not been rigorously investigated, the antibacterial nature of thymol would suggest that these are probably valid uses.
Other claims for ajwain include relief from nasal congestion, bronchitis and asthma, helping to cure influenza and earache, fighting tooth decay (probably valid since it's used in toothpaste) and using the oil to relieve arthritis.
Oh yes, and it also has claims to be an aphrodisiac!
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