Utilization of Amino Acids from Foods by the Rat III. Methionine

Abstract

The percentage of methionine utilized by the weanling rat and protein-depleted rat from various protein preparations, cereal, legume and animal protein foods, supplementing a diet limited only in methionine, has been studied. The ingested methionine that was utilized differed by 10% or less for 8 of the 13 products when tested with the weanling rat as compared to the protein-depleted rat, and by 15 to 22% for the other 5 products tested by the two methods. The percentage of methionine utilized from various foods ranged from 44 for unheated soybean flakes to 79 for beef round, determined as the average of the two methods. The amount of methionine excreted in the feces (digestibility) was also determined and the percentage of the ingested methionine that was excreted ranged from 1.5 for beef rib to 19.4 for rolled oats. The significance of these studies for measurement of protein (amino acid) quality of foods is discussed.