Abstract: In this paper,purple yam was used as testing material.Anthocyanins from purple yam were extracted by acidic ethanol.The quadratic polynomial mathematical model of anthocyanins was set up and its extraction conditions were optimized by Box-behnken response surface method and Design-Expert 8.0.6 analysis software.On the basis of single-factor experiments,the relationships between main extraction conditions including extraction temperature (X₁),extraction time (X₂), ratio of solid to liquid (X₃), ethanol concentration (X₄) and hydrochloric concentration (X₅) were investigated.Results showed that their effects were in the order of X₅ > X₂ > X₄> X₃ > X₁.The optimal extraction conditions were obtained as follows:extraction temperature was 81 ℃,extraction time was 3.5 h,the ratio of solid to liquid was 1:25,ethanol concentration was 70%,hydrochloric concentration was 18‰.Under these conditions,the average yield of anthocyanins was 4.928 mg/g,the relative standard deviation was 0.31%,and the relative error was less than 1.0% compared with the mathematical model.

Key words: purple yam, anthocyanins, single-factor analysis, response surface method, extraction process