The chicken eggshell comprises calcified shell and shell
membranes including inner and outer membranes. These
membranes retain albumen and prevent penetration of
bacteria. Shell membranes are also essential for the formation
of eggshell. The organic matter of eggshell and shell
membranes contain proteins as major constituents with
small amounts of carbohydrates and lipids (Burley and
Vadehra, 1989). Bronsch and Diamantstein (1965) analyzed
uronic acid in eggshells and reported a significant
correlation between the uronic acid content and the breaking
strength of the shell. Uronic acid is a constituent sugar
of glycosaminoglycan. We have shown that the organic
matter of eggshell contains two glycosaminoglycans including
hyaluronic acid and chondroitin sulfate-dermatan
sulfate copolymer. Sialic acid is another carbohydrate
found in eggshell membranes (Itoh et al., 1990; Nakano
et al., 1994). However, little is known about the difference
in concentrations of sialic acid between the inner and
outer eggshell membranes. There is also limited information
available concerning variations in nitrogen concentrations
and amino acid composition among the organic
matter of eggshell and shell membranes. Eggshell and
shell membranes are non-edible by-products with little
saleable value. However, they may contain biologically active compounds. Better understanding of chemical
composition of these by-products is of basic importance.
Such knowledge may also be important for investigating
the biological role of eggshell and shell membranes. This
study was undertaken to analyze uronic acid, sialic acid,
nitrogen, and amino acids in the organic matter of eggshell
and the inner and outer shell membranes and to
compare analytical data among these samples.