Abstract:Ultrasonic-assisted extraction of walnut shell pigment was investigated.Response surface methodology was used to optimize the process conditions based on single factor experiments.The stability of pigment solution to metal ions，DPPH radical scavenging ability，and the reducing power were used to study the properties of the pigment，to provide an experimental basis for industrial production and application of walnut shell pigment.Single factor experiments confirmed that ethanol concentration，extraction time，and extraction temperature were the main influencing factors.Using response surface methodology combined with actual operation，the optimal conditions were determined to be ethanol concentration，47%；extraction temperature，51 ℃；and extraction time，55 min.Under optimal conditions，the extraction rate of pigment was 1.65%.The results showed that Mg2+，Na+，Al3+，Zn2+，Ca2+，and K+had no effect on the pigment solution，whereas Fe3+and Cu2+could precipitate the pigment solution.The DPPH radical scavenging rate of the pigment was 73% at a concentration of 12.5 μg/mL.It had a certain reduction ability，but it was weaker than vitamin C.