September 2011 Issue
Soyfoods Made Easy — A Soy Primer
By Densie Webb, PhD, RD
Today’s Dietitian
Vol. 13 No. 9 P. 52
According to the Soyfoods Association, the U.S. market for soyfoods reached upwards of $4.5 billion in 2009. Yes, that’s billion with a “B.”
This number could climb even higher thanks to the message from the 2010 U.S. Dietary Guidelines to include more plant foods in the diet. But U.S. soy use is low compared with consumption in Asian countries, where entire shops are devoted to all things soy.
Years ago, the term “soyfoods” conjured up less-than-tasty meat analogues, blubbery blocks of tofu, and bitter-tasting soymilk. Today, the variety seems endless and far more appealing. While that’s good for your patients and clients, it can leave you scratching your head trying to answer questions about the difference between soy protein isolate and soy protein concentrate. Not to mention knowing about okara and yuba or which soyfood contains the most isoflavones—the naturally occurring phytonutrients found almost exclusively in soy, which research suggests may provide a variety of health benefits.
The evidence linking soy protein and coronary heart disease prevention is strong enough that the FDA approved a food labeling health claim for soy in 1999. Any product that is low in fat, saturated fat, and cholesterol and contains at least 6.25 g of soy protein is qualified to carry the claim. The heart benefit is believed to be due to the soy protein rather than soy’s isoflavone content. Isoflavones alone haven’t proven to be beneficial to heart health.
Today’s Dietitian has put together a soy primer to guide you through the increasingly complicated maze of soy and soy products.
Soyfoods
Edamame
These are larger soybeans that are harvested while the beans are still green and sweet tasting. They’re sold frozen, either still in the pod or shelled, and can be rinsed and boiled or steamed and seasoned to taste. Edamame works well as an appetizer or a snack. If prepared in the pod, simply squeeze the beans from the pod and eat with your hands.
Edamame is an excellent source of folate; a good source of protein, potassium, and choline; and low in calories. According to the USDA nutrient database, a 1/2 cup of edamame provides 6 g of protein, but check Nutrition Facts panels. Some brands contain as much as 10 g of protein per 1/2-cup serving. Because edamame is the whole soybean, it’s a rich source of isoflavones.
Natto
This product is made from small, fermented, cooked whole soybeans. It has a sticky, almost slimy coating and a cheesy texture. It’s typically found in Asian and natural food stores and sold in individual serving containers. Because of the thick, stringy texture of the coating on the beans, natto is usually stirred before serving. In Asian cultures, natto often is served as a breakfast food with rice.
Natto is rich in isoflavones and fiber; a good source of potassium, iron, calcium, vitamin C, and zinc; and low in calories and sodium.
One-half cup of natto provides 15 g of protein.
Miso
Miso is a thick, smooth paste made from soybeans; a grain such as rice, barley, or rye; salt; and a mold culture. The mixture is aged in cedar vats for one to three years. It’s used as a condiment and is a staple in Japanese cooking. Miso paste can be found in jars and plastic delilike containers or packages.
Miso can be used to flavor soups, sauces, dressings, and marinades or in place of anchovy paste, salt, and soy sauce in recipes. Miso should be refrigerated after opening.
Because it’s used in small amounts, it contributes little nutritionally. However, it’s extremely high in sodium: A mere 1/8 cup contains 1,282 mg of sodium.
As far as protein, miso provides 4 g. It’s a source of isoflavones, though it provides less than edamame or natto.
Okara
Okara is a dried pulp fiber with a texture similar to shredded coconut that’s a by-product of the processing of soymilk. By itself, it’s relatively bland and can be added to cookies or muffins to add fiber. It’s also available “wet” but is harder to find in this preparation. You won’t find okara in the supermarket; it’s most likely to be found in Asian food markets and online.
Okara has less protein than whole soybeans but is still protein rich, providing about 27 g of protein per 31/2 oz dried. It’s also extremely high in fiber but low in isoflavones.
Soymilk
To produce soymilk, soybeans are soaked, finely ground, and then strained. Soymilk comes in a variety of flavors, including vanilla, chocolate, coffee, chai, green tea, and, over the holidays, soy nog (as in egg nog). There are also light varieties with fewer calories.
Soymilk can be used in place of milk in cereal or coffee. It can be substituted equally in recipes in which milk isn’t a major ingredient, but there likely will be a taste difference. The taste of soymilk varies from one brand to the next, with some being sweeter than others.
Soymilk isn’t nutritionally equivalent to cow’s milk, though soymilk fortified with vitamins B12 and D and calcium comes close. If it’s fortified with other nutrients, it can provide even more nutrition than cow’s milk.
A 1-cup serving provides about 6 to 7 g of protein. Flavored soymilks will contain added sugar at about 21/2 tsp per 1-cup serving. Plain soymilk contains the equivalent of only 11/2 teaspoons of sugar, which is naturally present in the product.
Soymilk contains very little isoflavones but is low in saturated fat and, like all soyfoods, is cholesterol free.
Soynuts
Soynuts are whole soybeans that have been soaked in water and then baked until brown. They are similar in taste and texture to peanuts and available in a wide range of flavors, from barbecue to jalapeño and cheddar to chocolate and cherry. They are available in large supermarkets as well as health foods stores and online.
Like roasted nuts, no preparation is needed. Soynuts can be eaten as a snack or chopped up and used in recipes. But as with any nut, portion control is key. When eaten as a snack straight from the bag, the fat and calories can add up.
A 1/2 cup of soynuts provides 34 g of protein. Calories, fat, and sodium vary depending on the flavor. A 1/2 cup of plain roasted soynuts is also an excellent source of folate, potassium, and vitamin K; a good source of iron and zinc; and a source of calcium. Among the soyfoods, it’s one of the richest sources of isoflavones.
Soy Sauce (Tamari, Shoyu, Teriyaki)
Soy sauce is a dark-brown liquid made from fermented soybeans. Tamari, shoyu, and teriyaki are types of soy sauce. Shoyu is a blend of soybeans and wheat, and tamari is a by-product of making miso. Teriyaki often contains other ingredients, such as sugar, vinegar, and spices, and, as a result, is thicker.
Soy sauce is readily available in most supermarkets as well as in Asian markets. Look for low-sodium versions, which contain about 50% less than the regular versions.
A common ingredient in many Asian dishes, soy sauce should be used sparingly because of its high sodium content.
Despite being a soy product, soy sauce contains no isoflavones and virtually no protein. It’s low in calories (about 8 to 11 per tablespoon) but provides 900 to 1,000 mg of sodium per tablespoon.
Soy Sprouts
Soy sprouts are similar to bean sprouts or alfalfa sprouts but aren’t as readily available. They’re likely to be found in health foods stores or Asian stores.
Soy sprouts should be washed well before being used to top salads or in sandwiches because they can be contaminated with Listeria.
They’re rich in vitamin C and protein, providing 9 g per cup. One cup of soy sprouts also provides 90 kcals, of which more than 40% comes from fat.
Tofu
Tofu is a soft, cheeselike food that’s also known as soybean curd. It’s made by curdling fresh, hot soymilk with a coagulant. It comes in aseptic brick packages in several consistencies—extra firm, firm, soft, or silken.
Firm tofu is dense and solid and holds up well in stir-fry dishes, soups, or on the grill—anywhere you want the tofu to maintain its shape. Soft tofu is a good choice for recipes that call for blended tofu or in Oriental soups. Silken tofu is a creamy, custardlike product that works well in puréed or blended dishes and smoothies and as a replacement for sour cream in dips.
When a calcium salt is used as the curdling agent, tofu is an excellent source of calcium, providing as much as 200 mg per 4-oz serving. Extra firm and firm tofu are higher in protein, fat, and calcium than other forms. Generally, the softer the tofu, the lower the fat content. All tofu is a rich source of protein and isoflavones.
Tempeh
Whole soybeans are sometimes mixed with a grain such as rice or millet and fermented to form a chunky, tender soybean cake with a smoky or nutty flavor called tempeh. Traditionally an Indonesian food, it should be kept refrigerated and can be marinated and grilled; added to soups, casseroles, and chilis; or sliced and put on sandwiches.
Tempeh is easiest to find in Asian markets or health foods stores. While most tempeh is plain, flavors such as basil, red pepper, and curry are also available when ordered online.
Tempeh is rich in protein (10 grams per 2 oz) and isoflavones and low in sodium. It provides about 110 kcals per 2-oz serving.
Yuba
Yuba, also known as “foo jook” and considered a luxury in China and Japan, is fresh or dried thin layers of the translucent skin of soybean milk made by lifting and drying the layer formed on the surface of soymilk that has been heated and then cooled. It’s usually available only in Asian markets and sold as fresh or dried sheets, sticks, or chips.
Fresh yuba is sometimes used with other ingredients to make yuba rolls or it can be folded and dipped in soy sauce and eaten as is. If dried, it must first be reconstituted, which alters the texture compared with the fresh version.
Yuba is rich in protein and, when cooked, has an isoflavone content similar to tofu.
Soy Ingredients
Soy Flour
Made from roasted soybeans ground into a fine powder, there are three types of soy flour: full fat; low fat, which contains about one-third the amount of fat as full fat; and defatted. It comes in small bags and can be found in the baking or natural foods section of the supermarket.
Because it’s gluten free and higher in fat than wheat flour, it can’t fully replace the wheat or rye flour called for in recipes. Even recipes specifically developed to use soy flour may call for only 30% soy flour and the rest as wheat flour.
Full-fat soy flour is 40% protein, low-fat soy flour is 52% protein, and defatted soy flour is 55% protein compared with enriched white flour, which is 12% protein, and whole wheat flour, which is 16% protein.
Soy flour is rich in protein (30 to 40 g per cup), dietary fiber, and isoflavones. It’s also a good source of folate, potassium, and phosphorus.
Soy Protein Isolate
Soy protein isolate is protein removed from defatted soy flakes. It’s bland in flavor and added to processed foods such as shakes, energy bars, and cereals to boost the protein content. It’s available as a plain powder sold in canisters in health foods stores and natural supermarkets.
Soy protein isolate is rich in protein (23 g per ounce, or 90% protein) and phosphorus and is a good source of isoflavones.
Soy Protein Concentrate
Like soy protein isolate, soy protein concentrate comes from defatted soy flakes. It contains 70% protein and is higher in fiber than soy protein isolate. Available in a powder or as flakes, it’s often an ingredient in snack or energy bars, breakfast cereals, and protein shakes.
The isoflavone content depends on how the concentrate is processed. Concentrate processed with water is rich in isoflavones; concentrate processed with alcohol is low in isoflavones.
Soy protein concentrate is rich in protein, though it provides less than soy protein isolate. It’s rich in folate and a source of fiber, calcium, iron, and magnesium.
— Densie Webb, PhD, RD, is a freelance writer, editor, and industry consultant based in Austin, Tex.
Creamy Pumpkin Curry Soup
Ingredients
1 tablespoon soybean oil
1 small onion, diced
16 ounces silken tofu (1 package)
15 ounces pumpkin puree (1 can)
1 medium apple, peeled, cored and sliced
2 cups low sodium vegetable or chicken broth
1 teaspoon curry powder
3/4 teaspoon ground black pepper
3/4 teaspoon salt
1/4 cup toasted pumpkin seeds (optional)
Instructions
Heat soybean oil in medium saucepan over medium heat. Add onion and cook for 2 to 3 minutes until soft. Place onion, tofu, pumpkin, apple, broth, curry powder, pepper and salt in blender. Puree for 1 minute until smooth. Return mixture to saucepan. Heat over medium heat, stirring occasionally, until soup begins to gently simmer. Do not boil. Ladle into bowls; top with pumpkin seeds, if desired.
Nutrition Per Serving (1-cup serving)
90 Calories, 5 g Protein, 11 g Carbohydrate, 3 g Fiber, 3.5 g Fat, 0 g Sat. Fat, 0 g Trans Fat, 0 mg Cholesterol, 360 mg Sodium
Edamame Hummus
Ingredients
2 cups frozen edamame (shelled), cooked according to package directions (10 oz package)
1/4 cup soybean oil
3 tbsp lemon juice
2 tsp garlic, chopped
3/4 tsp cumin, ground
1/2 tsp salt
Instructions
Puree edamame, oil, lemon juice, garlic, cumin and salt in food processor for 30 seconds, scraping sides twice, until almost smooth. Cover and refrigerate until ready to serve. Serve with pita triangles, crackers, baguette or raw vegetables.
Nutrition Per Serving (2 tbsp serving)
60 Calories, 2 g Protein, 3 g Carbohydrate, 1 g Fiber, 5 g Fat, 0 g Sat. Fat, 0 g Trans Fat, 0 mg Cholesterol, 90 mg Sodium
Party-Perfect Tofu Skewers
Ingredients
1 package extra firm tofu (20 oz), drained and cut into 42, 1-inch cubes
2 tbsp lime juice
1 tbsp soybean oil*
1 tbsp reduced sodium soy sauce
14 bamboo skewers
1 cup Soynut Satay Dipping Sauce (recipe follows)
Additional soy sauce and oil for brushing
Instructions
Place tofu, lime juice, oil and soy sauce in large bowl; gently stir to coat. Cover and refrigerate, stirring occasionally, for 2 hours or overnight. Assemble 3 tofu cubes on each skewer. Brush grill with oil. Preheat grill to medium. Grill over medium heat for 3 minutes, turning frequently and brushing with soy sauce and oil, until golden brown. Serve with Soynut Satay Dipping Sauce.
Nutrition Analysis per Serving (1 satay and 1 tbsp sauce)
100 Calories, 7 g Protein, 3 g Carbohydrate, 2 g Fiber, 8 g Fat, 1 g Sat. Fat, 0 g Trans Fat, 0 mg Cholesterol, 115 mg Sodium
Soynut Satay Dipping Sauce
Ingredients
1/2 cup soynut butter
1/4 cup fresh lime juice
1 tbsp soybean oil*
1/4 cup rice vinegar
1/4 cup water
2 tbsp reduced sodium soy sauce
1/4 cup fresh green onion, chopped
1 1/2 tsp fresh ginger, grated
1 tsp fresh garlic, chopped
To prepare Soynut Satay Dipping Sauce: Pulse all ingredients in food processor until smooth. Place in small bowl. Cover and refrigerate.
* Often labeled “vegetable oil”
Nutrition Analysis per Serving (1 tbsp sauce)
60 Calories, 2 g Protein, 2 g Carbohydrate, 1 g Fiber, 4.5 g Fat, 0.5 g Sat. Fat, 0 g Trans Fat, 0 mg Cholesterol, 75 mg Sodium
Recipes reprinted with permission of the United Soybean Board