Firm, extra firm, soft. I'm not taking about mattresses; I'm talking about varieties of tofu. If you want to try tofu as an alternative to meat, how do you choose, and what do you do with it?

Tofu (Chinese for dou fu or bean curd) has been around for a long time, but tofu has gone mainstream, and the choices are limitless. Tofu is made by adding a curdling agent to soy milk, in a process similar to making cheese from milk.

CHRIS ROSENBLOOM FIT TO EAT Have a question of general interest? E-mail Rosenbloom Related: • More on food and drink • Restaurant reviews and search More Rosenbloom You can work '101 Foods' into your diet  Know your nutrition: A quick quiz for fall  Three to be careful with in healthy diet  Grapefruit, cancer link considered preliminary  Beta carotene powers orange fruits, veggies  Our levels of the 'sunshine' vitamin decrease as we age  'Repair' muscles after long-distance running  Food-drug interaction an important issue  • Chris Rosenbloom, Ph.D., R.D., is a member of the nutrition faculty in the College of Health and Human Sciences at Georgia State University.

The curd that results comes in three varieties: firm, soft and silken. The difference is the ratio of water to soybeans and the type and amount of coagulants used in processing.

Firm and extra-firm tofu are best for stir-frying and grilling or dishes where you want tofu to maintain its shape. Soft tofu is good for recipes that call for blended ingredients, like dips, salad dressings or soups. Silken tofu has a custardlike texture and is used in foods that are pureed, like shakes, smoothies and desserts.

Tofu is bland and takes on the flavor of what it's paired with, making it very versatile. You can also find flavored tofu — I've seen barbecue, teriyaki and smoked tofu in my grocery store.

Most tofu is sold in the refrigerated section and is highly perishable, just like milk. Check the use-by date (just as you do when you buy milk) and store it in the refrigerator. Tofu usually comes in a 12- or 14-ounce tub, and once opened it should be covered in water and stored in a resealable container; the water should be replaced every day.

It can be stored for about five days, but frozen tofu will last about five months. You might find it more convenient to use an entire package in a recipe to avoid the hassle of storing leftovers. Tofu is also sold in aseptic packages, or freeze-dried, and doesn't require refrigeration, but once open it should be handled the same as tofu purchased in the refrigerated section.

To use tofu, squeeze out all the water. Restaurants often freeze tofu and then thaw and squeeze out the water; freezing gives the tofu a chewy texture. A half cup of tofu has 85 calories, 5 grams fat, 10 grams protein, 2 grams carbohydrates, 15 milligrams sodium and no cholesterol.

Most tofu is processed with calcium, and it has about 25 percent of the daily value of calcium per serving based on a 2,000-calorie diet. Tofu also contains plant chemicals known as isoflavones that act as weak estrogens. Don't be afraid to eat a serving of tofu if you have had estrogen-positive breast cancer, but don't take isoflavone supplements that contain more of these compounds than a serving of tofu.

The soy protein in tofu has been touted to reduce heart disease, but the effect of soy on cholesterol levels is modest. Eating tofu as a substitute for foods high in saturated fat and cholesterol is a better defense against heart disease than adding soy cheese to a greasy burger.

The soy foods organization (www.soyfoods.com) has some great suggestions for using tofu:

• Add chunks to soups and stews.

• Mash with cottage cheese for a sandwich spread.

• Marinate in barbecue sauce and grill.

• Stir silken tofu into low-fat sour cream for a topping for baked potatoes.

Another helpful Web site is www.soybean.org. Download a copy of the Soyfoods Guide for more information and great recipes for tofu.

Easy Lasagna
9 servings

Hand on: 30 minutes

Total time: 1 1/2 hours

1 (8-ounce) can mushrooms, chopped
1 1/2 cups zucchini, chopped
1 (14-ounce) package water-packed, firm tofu, drained
1 tablespoon lemon juice
1 tablespoon dried parsley flakes
1 teaspoon Italian herb seasoning
1/4 teaspoon black pepper
3/4 cup water
4 cups low-fat marinara sauce
1 (8-ounce) package lasagna noodles, uncooked
1 (8-ounce) package mozzarella-style soy cheese, grated
1/4 cup Parmesan-style soy cheese

Preheat oven to 350 degrees. Cook the mushrooms and zucchini in a nonstick skillet until tender, adding a little water if needed. Set aside. Mash the tofu in a small mixing bowl. Add the lemon juice, dried parsley flakes, Italian herb seasoning and pepper. Mix well. Combine the water and marinara sauce. (The extra water will be absorbed by the uncooked noodles.)

To assemble the lasagna: Put about one-third of the sauce on the bottom of a 9-by-13-inch baking dish. Top with half the uncooked noodles, half the tofu mixture, half the mozzarella-style soy cheese and all the mushrooms and zucchini. Put another third of the sauce on top, the remaining noodles, remaining tofu and the last third of the sauce. Top with the remaining mozzarella-style cheese and the Parmesan-style soy cheese. Cover the dish with foil. Bake at 350 for 1 hour. Remove from oven and let sit 10 to 15 minutes to make serving easier.

— www.soyfoods.com (Click on recipes)