RELATIONSHIP OF EGGSHELL ULTRASTRUCTURE AND SHELL STRENGTH TO THE SOUNDNESS OF SHELL EGGS

Factors affecting the soundness of shell eggs are of primary concern t o egg processors due to substantial financial losses from cracked and leaker eggs. Ultrastructural analyses were used to examine the palisad e layer width and mammillary knob layer thickness of sound, cracked, a nd leaker eggshells. Subjective observations were also made. There was no significant difference (P > 0.05) in the width of the palisade lay er or the mammillary knob layer among sound, cracked, and leaker eggsh ells. The eggshell strengths of sound, cracked, and leaker eggs were e valuated using puncture force and shell thickness measurements. Sound eggshells were found to have a significantly (P < 0.05) higher mean pu ncture force (35.3 N) than cracked (30.4 N) and leaker (28.4 N) eggshe lls. The mean puncture force values for cracked and leaker eggshells w ere not significantly different from each other (P > 0.05). Regression and correlation analyses indicated a significant correlation (P < 0.0 1; r = 0.61) between palisade layer width and puncture force. The mean shell thickness values for cracked (0.36 mm) and leaker (0.35 mm) egg s were significantly lower (P < 0.05) than those of sound eggs (0.38 m m), although cracked and leaker eggshell thickness did not differ sign ificantly (P > 0.05). The correlation coefficient between puncture for ce and shell thickness was significant (P < 0.01; r = 0.56), indicatin g a possible relationship.