Widely used in Indian cooking, authentic Indian curry powder is freshly ground each day and can vary dramatically depending on the region and the cook. Curry powder is actually a pulverized blend of up to 20 spices, herbs and seeds. Among those most commonly used are cardamom, chiles, cinnamon, cloves, coriander, cumin, fennel seed, fenugreek, mace, nutmeg, red and black pepper, poppy and sesame seeds, saffron, tamarind and turmeric (the latter is what gives curried dishes their characteristic yellow color). Commercial curry powder (which bears little resemblance to the freshly ground blends of southern India) comes in two basic styles: standard and, the hotter of the two, Madras. Since curry powder quickly loses its pungency, it should be stored, airtight, no longer than two months.
From The Food Lover's Companion, Fourth edition by Sharon Tyler Herbst and Ron Herbst. Copyright © 2007, 2001, 1995, 1990 by Barron's Educational Series, Inc.