EFFECT OF PACKAGING MATERIALS AND STORAGE CONDITIONS ON THE MOISTURE SORPTION ISOTHERM OF SOLAR DRIED TABLE EGG POWDER

Kenawi, M.A., Zaghlul, M.M.A., Abdel-Hameed, S.M.

Abstract
    Moisture sorption isotherms of solar dried whole egg, egg white and egg yolk stored in different packaging materials at 25°C and relative humidity (RH) range from 22.50 to 92.50%were investigated. The water vapour transmission rate (WVTR) of the packaging materials was also determined at the same storage conditions. The data showed an increase in the (WVTR) values along with increasing the RH levels. The values were slightly high for the LDPE, whereas, there was no marked difference in the WVTR values for both HDPE and laminated polyethylene / nylon bags. The equilibrium moisture content (EMC) values for all samples were slightly high in the egg white, followed by whole egg and egg yolk. The (EMC) values for the samples increased with increasing the storage relative humidity. However, an inverse relationship was observed between the storage relative humidity and the time required to reach equilibration for all samples. The isotherm curves had sigmoidal shapes typical for food and all curves followed similar patterns. The data also showed that the appropriate RH for storage of solar dried egg samples under the previous storage conditions should be below 33% using suitable packaging materials with low water vapour transmission rate such as HDPE or laminated polyethylene / nylon bags.

Key words: Packaging materials, table egg, sorption isotherm, storage