Optimization of extraction technology for insoluble dietary fiber from peel of Pitaya by response surface methodology

The sequential treatment with alkaline followed by acid was applied to extract insoluble dietary fiber( IDF)from the peel of pitaya and main process conditions were optimized by single- factor experiments combined with response surface methodology. The extraction rate and purity of IDF were investigated with respect to Na OH concentration,alkaline extraction time,alkaline extraction temperature,alkaline extraction liquid- to- material ratio,acid extraction temperature,acid extraction time and acid extraction liquid- to- material ratio. The results showed that the optimal extraction conditions were Na OH concentration of 4.3%( g / g),alkaline extraction temperature46.5 ℃,alkaline extraction time 60 min,alkaline extraction material- to- liquid ratio 15 ∶ 1( m L / g),acid extraction temperature 77.4 ℃,acid extraction time 1.5 h and acid extraction material- to- liquid ratio 15∶1( m L / g).Under the optimal extraction conditions,the yield and purity of IDF were 30.29% and 94.78%,respectively.