Optimization of Extraction Technology of Eggplant Peel Pigment by Response Surface Analysis and Research on Its Stability

4% citric acid is selected as extraction solvent of eggplant peel red pigment from the alternative extraction solvents in the experiment,the absorbance value is measured at 530nm.On the basis of single factor experiment,60℃is selected as temperature;the material granularity,material-liquid ratio and extraction time are taken as the independent variables and response surface methodology is used to optimize the extraction technology of red pigments from fresh eggplant peels.The optimal extraction conditions are as follows:70 meshes of material granularity,1∶33.47(g/mL)of material-liquid ratio and 2.38h of extraction time.Under these conditions,the predicted and experimental absorbance values of extracts are 0.687 and 0.681respectively.Stability experiment shows that red pigment is stable in acidic solvent(pH3),but unstable in high temperature and with the existence of oxidant and reductant.Low-concentration food additive has little effect on the pigment,while highconcentration sodium benzoate and sucrose have great effect on the pigment.