An HPLC system was used in the determination of amino acid pro-files after hydrolysis of samples with 6 M HCl as described by Bidlingmeyer, Cohen, and Tarvin (1984). The cysteine and methionine
contents were determined after performic acid oxidation (Gehrke, Gehrke, Wall, Absheer, & Kaiser, 1985) and tryptophan content was determined after alkaline hydrolysis with the procedure of Landry and Delhaye (1992).