Patent ID: 7393659

Claim:
A method for determining the digestibility of proteins in a nutritional product comprising the steps of: a) providing a sample of a nutritional product that contains protein and a reagent blank; b) separately digesting the sample of a nutritional product and the reagent blank with at least one protein-degrading enzyme; c) terminating each said digestion process to obtain a digested sample and a digested reagent blank; d) removing a first portion from each of said digested sample and said digested reagent blank in step c); e) determining the concentrations of at least 18 different amino acids, including tryptophan, for each of said first portions obtained from said digested sample and said digested blank in step d); f) removing a second portion from each of said digested sample and said digested reagent blank in step c); g) separating each of said second portions from step f) into a liquid phase and a solid phase; h) determining the concentrations of said at least 18 different amino acids, including tryptophan, soluble in the liquid phases obtained from said second portions of said digested sample and said digested reagent blank in step g); i) calculating the percent digestibility of the protein in the nutritional sample by: 1) adding the concentrations of said at least 18 different amino acids, for each of said first portions obtained from said digested sample and said digested reagent blank in step e) to provide a sum that is the total amino acid concentration in each of said digested sample and said digested blank; 2) determining the difference between the total amino acid concentrations of the first portions of each of digested sample and the digested reagent blank in step 1; 3) adding the concentrations of said at least 18 different amino acids soluble in each of the liquid phases obtained from said second portions of said digested sample and said digested reagent blank in step h); to provide a sum that is the soluble amino acid concentration in each of said second portions of said digested sample and said digested blank; 4) determining the difference between the soluble amino acid concentrations of the said second portions from said digested sample and the digested reagent blank; 5) dividing the difference between the soluble amino acid concentrations of step 4) by the difference between the total amino acid concentrations of step 2) to obtain a quotient; 6) multiplying the quotient by 100, thereby determining the protein digestibility of a nutritional sample.