There are four soy proteins used when making soy products. Some of these proteins are available in powder, flake or pill form while others are added during production itself. The four main protein forms are:

• Hydrolyzed soy protein. The soy protein is broken down into amino acids in a chemical process called hydrolysis. Hydrolyzed soy protein also contains other substances such as monosodium glutamate MSG (MSG). Food products made with hydrolyzed soy protein are not required to list MSG on their nutrition labels. It is a popular taste enhancer in the food industry. It is not considered to be the best source for soy protein or nutrients.

• Soy protein concentrates. Made from defatted soybean flakes, this concentrate is commonly found in frozen soy “burgers.” It contains mainly soy protein (70 percent protein), along with some soy fiber.
  
  
• Soy protein isolate. Manufactured by removing the soy protein from defatted soybean flakes. It contains nearly 90 percent soy protein and is the most highly refined source of soy protein. Soy protein isolate is most commonly used as an ingredient in soy protein bars, soy protein shakes and other soy beverages.
  
  
• Textured soy protein. Products made from textured soy flour, which is manufactured by processing defatted soy flour in an extrusion cooker. Methods for making textured soy protein may vary.