Detection of incubator reject eggs by differential scanning calorimetry

Abstract

A method to detect the presence of incubator reject (IR) eggs in fresh egg white by differential scanning calorimetry (DSC) was described. The transition temperature of denaturation (Td) of ovalbumin of fresh shell egg white was observed by DSC to be 83°C. After eggs had been in an incubator (38°C) for at least 4 days, the ovalbumin changed to S-ovalbumin and the denaturation temperature (Td) of the endotherm peak increased to 91°C. Incubation for two days resulted in the transformation of ovalbumin (Td 83°C) into an intermediate state (Td 87°C). In processed egg white (EW), thermograms showed only partial transformation of ovalbumin to the intermediate state which appeared as a split peak or shoulder with a Td of 87°C. In IR eggs, the ovalbumin was completely transformed into S-ovalbumin. In mixtures of egg white from fresh and incubator reject eggs, DSC could detect the two species as a split ovalbumin peak with Td 83°C and Td 91°C. Adulteration of egg-white products with as little as 7% incubator rejects can be detected by DSC. © 1992.