Study on technology of extracting soluble dietary fiber from peel of pitaya by ultrasonic wave

Soluble dietary fiber(SDF) from the peel of pitaya and main process conditions were optimized by single-factor experiments combined with response surface methodology. The yield of SDF were investigated with respect to extraction time,extraction temperature,extraction material-to-liquid ratio,p H,power of ultrasonic wave. The yield of SDF was 26.45%,when the extraction substance with a ratio of liquid to solid 20 ∶1(m L/g)and p H3.3 was processed by ultrasonic wave power 400 W at 67 ℃ for 50 min before precipitating 2 h using95% ethanol and centrifuging 20 min with 4000 r/min,then washing sediment by 75% ethanol. This indicated that soluble dietary fiber could be extracted from peel of pitaya effectively with this method.