For more than 2,000 years, rice producers in India and Pakistan have parboiled nonaromatic varieties before they remove the hull and mill them to white rice. They steep the freshly harvested grain in water, boil or steam it, and then dry it again before hulling and milling. This precooking brings several advantages. It improves the nutritional quality of the milled grain by causing vitamins in the bran and germ to diffuse into the endosperm, and causing the aleurone layer to adhere to the grain. Precooking the starch also hardens the grain and makes its surface less sticky, so when cooked again, parboiled rice produces separate firm intact grains. Parboiled rice also has a distinctive nutty flavor; the soaking activates enzymes that generate sugars and amino acids that then participate in browning reactions during drying; and partial breakdown of lignin in the attached hull provides vanillin and related compounds. Parboiled rice takes longer to cook than ordinary white rice, a third to half again the time, and its texture is so firm that it can seem coarse.