No abstract

The organic matrix from normal and pimpled calcified chicken eggshells were dissociated into acid-insoluble, water-insoluble, and facultative-soluble (both acid- and water-soluble) components, to understand the influence of shell matrix on eggshell qualities. A linear correlation was shown among these 3 matrix components in normal eggshells but was not observed in pimpled eggshells. In pimpled eggshells, the percentage contents of all 4 groups of matrix (the total matrix, acid-insoluble matrix, water-insoluble matrix, and facultative-soluble matrix) were significantly higher than that in normal eggshells. The amounts of both total matrix and acid-insoluble matrix in individual pimpled calcified shells were high, even though their weight was much lower than a normal eggshell. In both normal and pimpled eggshells, the calcified eggshell weight and shell thickness significantly and positively correlated with the amounts of all 4 groups of matrix in an individual calcified shell. In normal eggshells, the calcified shell thickness and shell breaking strength showed no significant correlations with the percentage contents of all 4 groups of matrix. In normal eggshells, only the shell membrane weight significantly correlated with the constituent ratios of both acid-insoluble matrix and facultative-soluble matrix in the whole matrix. In pimpled eggshells, 3 variables (calcified shell weight, shell thickness, and breaking strength) were significantly correlated with the constituent proportions of both acid-insoluble matrix and facultative-matrix. This study suggests that mechanical properties of normal eggshells may not linearly depend on the organic matrix content in the calcified eggshells and that pimpled eggshells might result by the disequilibrium enrichment of some proteins with negative effects.

Glycosaminoglycans (GAG) are linear, highly negatively charged polysaccharides that may perform an important role in biomineralization. GAG were isolated from chicken eggshell membranes and calcified shells. Disaccharide compositional analysis was performed using liquid chromatography-mass spectrometry. All 4 groups of GAG -hyaluronan (HA), keratan sulfate (KS), chondroitin sulfate (CS), and heparan sulfate (HS) -were detected in shell membranes and in calcified shells. HA was the most plentiful GAG in shell membranes, and CS was the most abundant in calcified shells. The CS present, in both membranes and calcified shells, consisted primarily of 6S CS-C , 4S CS-A , and 0S CS-0 disaccharides. Neither 4S6S CS-E nor 2S CS was detectable in shell components. Small amounts of 2S4S CS-B were detected in membranes and TriS CS , and 2S4S CS-B and 2S6S CS-D were detected in calcified shells. HS in calcified shells contained all disaccharides except for 2S6S. In shell membranes, HS contained primarily NS and 0S as well as small amounts of TriS, NS2S, NS6S HS , and 6S, but neither 2S6S nor 2S was detectable. The disaccharide composition of membrane CS, as well as membrane and calcified shell HS, were very similar in all eggshells. In contrast, the composition of calcified shell CS disaccharides was highly variable. In membranes, both HA and KS content showed a correlation with egg shape index. The 4S CS-A content correlated with eggshell strength, and 0S CS-0 correlated with eggshell strength and calcified shell thickness. HS content and its disaccharide composition showed no apparent correlation to properties of calcified shells. In calcified shells, only HS 6S correlated with egg shape index. This study suggests that GAG content and disaccharide composition of shell membranes might impact the quality of chicken eggshells.