Protein quality and the cost of selected commercial protein supplements.

The biologic value and the cost of three commercial protein supplements were compared using casein as the control. Each product was fed to rats as the sole protein source supplying 10 percent of the energy in a semipurified diet. Nonfat dry milk was equal to casein in PER, but the PERs of low-fat soy powder and high-protein supplement were significantly lower than the PER of casein. Nitrogen balance was positive for all protein supplements, but low-fat soy powder was significantly lower than the others. cost comparison per gram of protein showed low-fat soy powder to be the least expensive, nonfat dry milk to be slightly higher in cost, and the high-protein supplement to be the most expensive.