The Application of Ultrasound Pretreatment and Pulse-Spouted Bed Microwave Freeze Drying to Produce Desalted Duck Egg White Powders

Abstract

Fresh duck egg white (FDEW) powders and desalted duck egg white (DDEW) powders were produced by using a novel pulse-spouted bed microwave freeze dryer and a conventional freeze dryer. The desalting process of the salted egg white was carried out in the presence or absence of ultrasound pretreatment. The drying time, microstructure, apparent density, color, and functional properties (gelling, foaming, and emulsifying) of FDEW and DDEW powders obtained from both the pulse-spouted bed microwave freeze-drying (PSMFD) and a conventional freeze-drying (CFD) were studied in order to evaluate the physicochemical and functional properties of these powders. The results show that PSMFD produced FDEW powders with better color appeal (higher L* and lower b*), lower apparent density, as well as shorter drying time compared to the FDEW powders produced by the CFD. FDEW powders produced from PSMFD produced more transparent gels, emulsions with higher foam stability, and higher emulsifying activity index compared to the FDEW powders obtained from CFD. Regarding the powders obtained from DDEW by using PSMFD, the ultrasound pretreatment during the desalting process produced DDEW powders with higher gel strength, higher foaming capacity, higher foam stability, higher emulsion stability index, as well as shorter drying time compared to the DDEW powders in which ultrasound treatment was not carried out during the desalting process in the upstream.