Abstract: In order to optimize the extraction of pectin from citrus peel as an agricultural waste by simultaneous hydrolysis with cellulase and hemicellulase, the effects of three key factors including extraction time, temperature and total enzyme amount on the extraction rate of pectin were explored by Box-Behnken experimental design based on Placket-Burman design, by which the optimal initial pH, mass ratio of cellulase and hemicellulase, ratio of solid to liquid and material granularity were determined to be 4.5, 1:1, 1:20, 60 mesh, respectively. As a result, a mathematical model describing the relationship between the above three factors and the extraction rate of pectin was established. Based on canonical analysis of the model, the optimal extraction conditions were determined to be 0.46% total enzyme amount, 5.1 h extraction time and 41 ℃ extraction temperature. Under the optimal extraction conditions, the predicted maximum yield of pectin was 12.35%, which was close to the actual value of 12.22%. Meanwhile, each tested physical and chemical index of obtained pectin reached or even exceeded the requirements of the national standards.

Key words: citrus peel, pectin, double enzymatic extraction, Placket-Burman experimental design, response surface methodology, mathematical model