A Comparison of the Nutritional Value of Protein from Several Soybean Fractions

Fractions studied were the following: full-fat soy flour (dehulled soybeans), soymilk (water-extract of soybeans), residue from water extraction, acid-precipitated curd from soymilk and whey protein left from the alcohol precipitation of the whey. All fractions were heated for one hour at 100°C and a series of protein concentrations in the diets (10, 20 and 30%) were tested to determine the quality of protein found in the various fractions. The residue contained the highest quality of protein as measured by growth and protein efficiency ratio. Diets containing residue were very acceptable to growing rats. Soymilk and curd protein were inferior to the residue and to the dehulled soybean protein. Poor growth was obtained with whey protein.