Effect of egg shape index on mechanical properties of chicken eggs

Eggs are available in different shapes. These shapes can be differentiated using a shape index (SI). The shapes most often encountered are sharp, normal (standard), and round eggs which are enumerated on the SI as <72, 72-76, and >76, respectively. In this study, the effect of egg shape on the mechanical behaviour of chicken eggs under a compression load was investigated. The resistance of chicken eggs (Lohmann) to damage was determined by measuring the average rupture force, specific deformation, rupture energy and firmness along the X-front (X-f), X-back (X-b) and Z-axes at different compression speeds (0.33, 0.66 and 0.99 mm/s). The greatest amount of force required to break the eggs was required when eggs were loaded along the X-f-axis and the least compression force was required along the Z-axis. The specific deformation and rupture energy required for the eggs tested was lower along the X-f-axis than the X-b- or Z-axes. The highest measure of firmness in the eggs tested was found to be along their X-f-axis. The results indicated that when testing the effects of compression speed the rupture force is highly dependent on SI. The greatest force needed to rupture eggs was found in eggs with high SI values that were tested at low compression speeds. (c) 2007 Elsevier Ltd. All rights reserved.