Abstract: The extraction conditions of red pigment from Portunus trituberculatus shell were optimized by single factor test and orthogonal test,and the stability of the red pigment was analyzed.Results showed that the optimal extraction conditions are as follows:raw material size 80 mesh,ethanol concentration 60%,ratio of liquid to material 10:1(ml/g),extraction temperature 70℃ and extraction time 105 min.Under these conditions,the yield of the red pigment is 10.28%,and the color value is 13.1.The red pigment is stable to heat below 75 ℃,dark,sunlight and acid,it is decomposed easily by oxidant,reductant,and UV light,but alkaline condition,sugar and metal ions,such as K+ and Na+ can fortify its color;Fe3+ and Cu2+ can change its color.Ca2+,Mg2+,Al3+,Zn2+ and common food additives,such as citric acid,potassium sorbate can not affect it at all.High concentration of VC can make the red pigment precipitate.

Key words: Portunus trituberculatus, pigment, extraction, stability