The English word comes from the Arabic tamar-i-hind, “date of India.” For information on the plant itself, see the Glossary. In U.S. markets, tamarind sometimes comes in its original package, a brown beanlike pod with a brittle skin containing several seeds encased in a fibrous sweet-sour pulp. The more mature the tamarind, the darker and sweeter the pulp. It is also sold in blocks of compressed pulp, the Indian version very dark and dry, the Thai, moister and lighter. A third option is the commercial tamarind extract from Thailand and India. The Thai varieties, which I prefer, are thinner and fresher-tasting; the Indian ones are darker, thicker, and sometimes almost tarry.
To extract tamarind pulp from whole fruit, break the brittle covering off the whole seedpods and tear off the fibrous net around the pulp. (If you’re using compressed tamarind, simply break off the amount called for by the particular recipe.) Cover the tamarind with boiling water and let it steep for at least 30 minutes and up to a few hours. Or put it in a nonreactive pan, cover with water, and simmer over low heat for 15 to 20 minutes; then let it steep until it’s cool enough to handle. Break up the tamarind with your fingers and rub it through a stainless steel or nylon strainer into a bowl, scraping the bottom of the strainer to collect the pulp as you go. Moisten the residue with a little warm water and rub and push it through the strainer again.
Freshly extracted tamarind pulp keeps for at least a week in the refrigerator. Tamarind residue is used in many Indian households to clean brass and copper. Coarse salt and tamarind residue are particularly successful with copper.