Evaluation of Protein in Foods. X. Effects of Source and Concentration of Dietary Fat on Protein Efficiency Ratio (PER) Values

Abstract

Abstract Studies were conducted on the effects of the concentration and source of dietary fat on PER values. At the 20% level, degummed rapeseed oil depressed PER of isolated soybean protein or casein, whereas corn oil, lard, or margarine had no effect. In contrast to results with these proteins, 20% rapeseed oil had no effect on PER of fish flour. Covariance analysis and paired feeding studies showed that the effects of rapeseed oil on PER could be explained by its influence in reducing food consumption. The high level of rapeseed oil had no effect on efficiency of nitrogen retention, as measured by net protein utilization. Substitution of 10% rapeseed oil for 10% corn oil in standardized PER assays had no significant effect on PER values of peas, casein, or whole wheat flour. This finding provides assurance that in standardized assays, in which the level of dietary fat is set at 10%, PER values are not influenced by the composition of the dietary fat.