The mechanical properties of the thick white of the hen's egg

Abstract

1. 1. The thick white fraction of the egg consists of a gel in which a transparent phase is separated by a series of parallel bands of microscopic fibres. Its mechanical properties have been studied by measuring in a magnetic field the displacement of a minute nickel sphere inserted into the gel. 2. 2. The values of the rigidity in arbitrary units obtained in this way were converted indirectly into absolute units by means of parallel measurements on gelatin gels using, on the one hand, the magnetic particle method, and on the other, a method that measured rigidity in c.g.s. units. 3. 3. For stresses of short duration, the displacement of the particle was elastic in character in both the transparent phase of the thick white and in the bands. The thick white, therefore, is a weak gel interpenetrated by a system of microscopic, elastic fibres and not, as is usually believed, merely an entanglement network. 4. 4. The rigidities of the two types of structure in the thick white were different but both of them were related quantitatively to the proportion of thick white in the total white of the egg irrespective of whether the differences in this proportion were the result of the natural variation between newly-laid eggs or were caused by the effects of time and temperature after laying. 5. 5. It is concluded that the relation between rigidity and the proportion of thick white cannot be explained by the depolymerization of a simple ovomucin network.