MECHANICAL BEHAVIOR AND PHYSICAL PROPERTIES OF CHICKEN EGG AS AFFECTED BY DIFFERENT EGG WEIGHTS
Authors: ALTUNTAS EBUBEKIR , SEKEROGLU AHMET 
Published: July 2008

This study was carried out to determine the effect of egg weight on physical properties and mechanical behavior under compression of chicken eggs. Four different weights – including medium, large, extra large and jumbo – were used. Physical properties of chicken egg – such as size, geometric mean diameter, sphericity, volume, surface area, packaging coefficient of eggs, shape index, shell thickness and static coefficient of friction on various surfaces – were determined. The mechanical properties of chicken egg to compression as effected by egg weight were determined in terms of average rupture force, specific deformation and rupture energy along x‐ and z‐axes at different compression speeds. The length, width, geometric mean diameter, unit mass, surface area, egg volume and packaging coefficient increased as the egg weight increased. The average shape index and shell thickness values ranged from 78.37 to 79.56, and 0.400 to 0.387 mm for the eggs tested, respectively. The static coefficients of friction on various surfaces, namely, glass, plywood, galvanized metal, rubber and chipboard, increased linearly with increasing egg weight tested. The rubber surface presented the maximum friction followed by plywood, chipboard, galvanized metal and glass. The force required to initiate egg rupture on the z‐axis decreased as egg weight increased from medium to jumbo. The specific deformation and rupture energy values observed for chicken eggs compressed along the z‐axis were higher than the values obtained when testing eggs in the x‐back and x‐front orientations. The results indicated that the rupture force along all three axes is highly dependent on the egg weight over the compression speed ranges investigated.

PRACTICAL APPLICATIONS

The mechanical and physical properties of animal and plant materials are necessary considerations in the design and effective utilization of the equipment used in the transportation, processing, packaging and storage of agricultural products. Several factors – such as age, breed and weight of chicken – influence the size of an egg. Eggs are available in different sizes according to weight, including peewee, small, medium, large, extra large and jumbo. Even a slight shift in egg weight influences size classification which is one of the factors considered when eggs are priced. Egg size and the eggshell thickness are strongly related to each other. A chicken egg is a packaged food and an important quality aspect of the packaged egg material is the mechanical strength of the eggshell. Eggshell quality depends on egg size and weight. Egg properties such as shape index and shell thickness affect the proportion of damaged eggs during handling and transport. Eggshell strength has been described using various variables such as thickness of eggshell, shell stiffness and rupture force. Eggshells must be strong enough to prevent cracking in order to preserve the embryo until hatching. Shell strength is necessary to prevent damage from handling and to preserve eggs during transport from farm to market. As egg weight increases during the production period, eggshell thickness and breaking strength usually decrease. The rupture force of chicken eggs depend on various egg properties such as egg specific gravity, egg mass, egg volume, egg surface area, egg thickness, shell weight and compression speed. For this reason, egg production, processing and packaging systems must be designed while taking these criteria into consideration such as physical properties of eggs and their resistance to damage through mechanical shock.