Whey protein hydrolysate (WPH) is now considered as an important and special dairy protein ingredient for its nutritional and functional properties. The objectives of the present study were to investigate the effect of environmental relative humidity (RH) and storage temperature on the physicochemical stability of three WPH powders with hydrolysis degrees (DH) of 5.2%, 8.8% and 14.9%, respectively. The water sorption isotherms of the three WPH powders fitted the Guggenheim-Andersson-DeBoer model well. An increase in water content leaded to a decrease in glass transition temperature (Tg), following a linear Tg vs log water content relationship. Moreover, an increase in DH caused the decrease in Tg at the same water content. Changes in microstructure and colour occurred significantly when the WPH powders were stored at high environmental RH or temperature, especially for those with high DH.
Bibliographical noteFunding Information:
This research was supported by the National Natural Science Foundation of China ( 31071492 ), the Program for New Century Excellent Talents in University ( NCET-11-0666 ), the Research Project of Chinese Ministry of Education ( 113032A ), the Fok Ying Tung Education Foundation ( 121033 ), and the 111 project-B07029. The authors would like to thank Davisco Foods International, Inc. for supplying WPH powders, and appreciation is also extended to Gilbert Ahlstrand at University of Minnesota for technical assistance on SEM.
- Glass transition
- Water content
- Whey protein hydrolysate