The invention discloses a method for preventing
yolk of salted duck eggs from generating black circles. The method comprises the following steps of starting controlling the freshness of raw duck eggsfundamentally, so that the breeding of microorganisms can be reduced, and the
adverse effect caused by that the microorganisms
breed when being preserved and stored subsequently is reduced; then reasonably controlling the
salinity of preserving liquid, and preserving temperature, and under the assistance of ultrasonic
waves, performing preserving, so that the preserving time is greatly shortened,and the possibility that the
yolk of the duck eggs generates black circles is reduced; performing cooperation with the addition of a chelating agent, wherein when the preserving liquid penetrates intothe duck eggs, iron ions in the
yolk can be chelated, the condition that
hydrogen sulphide generated by
sulfur-containing amino acids in
egg white generates
ferrous sulfite to form the black circlesis avoided; finally, after heating for sterilizing in a water bath,
coating a layer of protecting liquid on the surfaces of duck egg shells, wherein the protecting liquid comprises
chitosan and
triethanolamine, so that the protecting liquid has good fresh keeping effect on the salted duck eggs, and the speed of generating the
hydrogen sulphide in the coated duck eggs is reduced or the condition ofgenerating the
hydrogen sulphide in the coated duck eggs is even avoided, the
grease oxidation is slowed down, the speed of breeding
bacteria is reduced, and the black circles are further restrained.