Salted egg is one of the most traditional and popular preserved
egg products in oriental countries. Orange color, oil exudation and
gritty texture are the desirable characteristics of salted egg yolk
(EY). During pickling, the yolk gradually becomes solidified and
hardened. The egg white (EW) loses viscosity and whipping capability
and becomes watery. The diffusion of salt into eggs and moisture
removal out of eggs happen simultaneously during pickling.
All changes occurring during pickling are most likely to determine
the preferential characteristics of salted egg. Conventionally, egg is
coated with a paste-like mixture consisting of red soil, salt, and
water or immersed into a solution containing salt for 20–30 days
at around 27 C (Chi and Tseng, 1998; Lai et al., 1999). The immersing
method is faster and more convenient for production of salted
egg. Differences in salt and nitrogen content, composition of lipids
and storage stability of salted EY of both conventional and immersion
methods have been compared (Peh et al., 1982). A higher salt
concentration in the immersion solution or coating paste results in
higher penetration rate of salt into EY. Dehydration and release of
lipids in EY increase as pickling time increasing and are more pronounced
than the paste coating method. Therefore, dehydration
and salt content could have been two major factors affecting the
properties of salted egg. The rate of pickling penetration into EW
and EY, and moisture reduction governed by pickling method
may have important influence on composition and characteristics
of egg, especially EY. Additionally, pickling time plays an important
role in the formation of salted egg during pickling. However, owing
to low energy efficiency, long processing time, quality deterioration
and environmental problems of present processing methods,
searching appropriate methods for treating eggs is still a challenge
to chemical and food process engineers