title: Changes in physical and gelling properties of freeze-dried egg white as a result of temperature and relative humidity.
abstract: 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 (Tg ) of FDEW decreased with increasing % RH. The colour of FDEW stored at 60 °C was darker yellow than those at 40 and 25 °C, particularly at high % RH. RH had no effect on hardness and water-holding capacity (WHC) of gels made from FDEW stored at 25 °C for 1 week. However, hardness and WHC of gels from FDEW stored at higher temperatures; 40 °C, 48% RH and 60 °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.
  
  
  CONCLUSIONS
  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. © 2016 Society of Chemical Industry.
authors: Department of Food Science and Technology, Faculty of Agro-Industry, Kasetsart University, Bangkok 10900, Thailand.
authors: Wattinee
authors: W
authors: Katekhong
authors: Department of Food Science and Technology, Faculty of Agro-Industry, Kasetsart University, Bangkok 10900, Thailand.
authors: Sanguansri
authors: S
authors: Charoenrein
mesh_terms: D003116:Color; D015387:Egg Proteins, Dietary / Q000032:analysis / Q000737:chemistry*; D004529:Egg White / Q000737:chemistry* / Q000191:economics; D063427:Food Quality; D061353:Food Storage / Q000379:methods*; D057141:Food, Preserved / Q000032:analysis*; D005612:Freeze Drying; D005782:Gels; D006244:Hardness; D006358:Hot Temperature / Q000009:adverse effects; D006813:Humidity; D015416:Maillard Reaction; D055585:Physical Phenomena; D066329:Protein Aggregates; D011487:Protein Conformation; D011489:Protein Denaturation; D013785:Thailand; D044366:Transition Temperature; D014867:Water / Q000032:analysis
chemical_list: D015387:Egg Proteins, Dietary; D005782:Gels; D066329:Protein Aggregates; D014867:Water
keywords: colour, storage; freeze-dried egg white; gelling properties; relative humidity; temperature