Gas chromatographic analysis of shell membrane amino acids from hard-shelled, soft-shelled, and shell-less eggs

The amino acid composition of shell membranes from hard-shelled (HS), soft-shelled (SS), and shell-less (SL) eggs produced by 62-wk-old hens was analyzed by gas chromatography using N-acetyl n-propyl ester derivatives. This technique succeeded in identifying tryptophane and ornithine as shell membrane components. There were no significant differences in the concentrations of any of the 17 amino acids analyzed among HS and SS eggs, HS and SL eggs, or SS and SL eggs. Stepwise discriminant analysis of the amino acid ratios correctly classified all of the amino acid chromatograms of shell membranes from HS/SL and SS/SL egg pairs, and 92.9% of the HS/SS and 90.0% of the HS/SS/SL amino acid chromatograms were classified correctly (F = 1.0). Higher F values reduced the percentage of correct classifications to 75.0%, 85.0%, and 67.5% (F = 2.0) for the HS/SL, SS/SL, and HS/SS/SL egg groups, respectively, and to 78.6% (F = 3.0) for the HS/SS egg group. Stepwise discriminant analysis also identified specific amino acid ratios that were most efficient at classifying the amino acid chromatograms according to shell type. This process identified three amino acid ratios for the HS/SS egg group (F = 3.0), two ratios for the HS/SL egg group, four ratios for the SS/SL egg group, and four ratios for the HS/SS/SL egg group (F = 2.0). Based on the number of times they appeared as efficient discriminating variables at higher F values, alanine, proline, and isoleucine seemed to be the most important amino acids for correctly classifying shell membranes by egg type.