The invention discloses a color-protecting
processing method of
freeze drying onion, wherein the method comprises the following steps of: immersing onion materials in an
alkaline water solution firstly; then bleaching slightly in an alkaline
warm water, cleaning, soaking by using a natural
reducing sugar solution and draining; then freezing the onion materials by adopting a
slow freezing mode; finally, freezing,
drying, dehydrating and
processing the frozen onion materials, wherein the
slow freezing mode is that the total freezing time is not less than 5 hours, and the central temperature of the onion materials after freezing is less than and equal to minus 22 DEG C. After the scheme is adopted, according to the invention, the acid degree is regulated through the
alkaline water solution firstly, and
chlorophyll is prevented from being subjected to de-magging to lead to the defect of green
fading of the materials, thus the green of the onion materials is kept to be stable, and the problem that the
metal content of the materials in the prior art exceeds the standard is overcome. Moreover, according to the invention, a non-toxic natural
reducing sugar solution is utilized as a
processing auxiliary material for protecting the color, the problem that the
sulfite residual quantity of the product after color-protection of the
freeze drying onion exceeds the standard is overcome, and the product safety is ensured.