Abstract: In order to improve the comprehensive utilization of walnut resource, the extraction of brown pigment from walnut shell was explored. On the basis of one-factor-at-a-time experiments, a three-variable quadratic equation was established by orthogonal regression design to describe the effects of ethanol concentration, temperature, extraction time and material-to-liquid ratio on the extraction rate of brown pigment. Through resolving the equation, the optimal conditions for extracting brown pigment from walnut shell were identified to be ethanol concentration of 52%, extraction time of 4.8 h, extraction temperature of 70 ℃, and material-to-liquid ratio of 1:5. Under the optimal conditions, the extraction rate of brown pigment was 5.0496%.

Key words: walnut shell, brown pigment, extraction technology, orthogonal regression design