Remember tofu? The bland, curdy stuff that looks like albino Jell-O, beloved by your vegetarian friends?

If you think that bean curd is only for Asians and health food fanatics, it's time to look again. Tofu is turning up at mainstream markets and top restaurants. My local supermarket recently began carrying tofu with Chinese spices and even one with French herbs.

There's good reason for tofu's new-found popularity. In this age of reduced meat consumption, tofu offers easily digestible protein without harmful fats or cholesterol. Tofu contains all eight essential amino acids. Its low calorie count (147 calories in an eight-ounce serving) is a boon to dieters. Tofu is an excellent source of calcium, but without the sodium and saturated fat of cheese. It's also an ecological food: an acre of soybeans provides 20 times as much usable protein as an acre used by cattle for grazing.

Tofu was invented in China, where it has been a dietary mainstay for 2,000 years. The Japanese are avid tofu consumers, as are Koreans and Southeast Asians. Once limited to Asian markets, tofu can now be found in the produce section of any major supermarket.

Tofu is also known as bean curd; the dairy metaphor is apt. To make it, fresh soybeans are soaked overnight, finely ground, and cooked with water to make soy milk. The soy milk is then separated into "curds" and "whey," using one of two natural coagulants: \o7 nigari \f7 (magnesium chloride extracted from sea water) or calcium sulfate (naturally mined gypsum). Tofu made with the latter is higher in calcium. The curds are then strained and pressed into the familiar ivory-colored, cobblestone-shaped cakes.

In the Orient there are literally dozens of types of tofu and tofu by-products, including malodorous fermented tofu and crepe-like bean curd skins. In this country, you'll find four basic types: extra-firm, firm, soft and silken. Extra-firm and firm tofu are intended for grilling, pan-frying, stir-frying and other preparations in which you want the bean curd to retain its shape. Soft tofu is great for cheese cakes and salad dressings, while silken tofu has a soft custardy consistency well suited to soups and desserts.

In the old days, buying tofu required fishing around in a water-filled tub at an Oriental market. (If you do buy it in bulk, be sure the packing liquid is clean and free of unpleasant odors.) Today, tofu is commonly sold in 1-pound blocks in convenient plastic containers. Refrigerate it until using and use by the date on the container. Once the package is opened, store the tofu in water to cover, changing the water daily. Use open bean curd within a week.