Changes in physical and gelling properties of freeze-dried egg white as a result of temperature and relative humidity

BACKGROUND: The quality of dried egg white with respect to functional properties can be affected by storage conditions. The effect of temperature and relative humidity (RH) on changes in colour and gelling properties in freeze-dried egg white (FDEW) during storage was investigated. RESULTS: The glass transition temperature (T-g) of FDEW decreased with increasing % RH. The colour of FDEW stored at 60 degrees C was darker yellow than those at 40 and 25 degrees C, particularly at high % RH. RH had no effect on hardness and water-holding capacity (WHC) of gels made from FDEW stored at 25 degrees C for 1 week. However, hardness and WHC of gels from FDEW stored at higher temperatures; 40 degrees C, 48% RH and 60 degrees C, 11% RH dramatically increased. These results related to the differential scanning calorimeter thermograms which showed a broadening peak with lower enthalpy of protein denaturation. Moreover, the protein's SDS-PAGE pattern in the samples stored at high temperatures or RH levels showed protein aggregation. CONCLUSION: Storage of FDEW at high temperature and RH levels induced protein conformation changes. These have contributed to protein aggregation which affected the gelling properties of FDEW. (C) 2016 Society of Chemical Industry