Optimization of Ultrasonic-Microwave Assisted Extraction of Procyanidins from Hops Residue

In order to optimize the extraction process of procyanidins from hops residue,the hops residue extracted from hops extract by supercritical CO₂ was used as the research object. Procyanidins were extracted by ultrasonic-microwave assisted ethanol extraction,and the content was determined by high performance liquid chromatography. Firstly,microwave power,microwave time,ethanol concentration,solid-liquid ratio,extraction temperature and extraction time were taken as single factors to study the effects of each factor on the extraction amount of procyanidins. On this basis,the extraction process was optimized by Plackett-Burman experimental design and Box-Behnken experimental design. The results showed that the optimal process for extracting procyanidins from hops residue by ultrasonic-microwave assisted was as follows:ultrasonic power 50 W,ultrasound-microwave treatment temperature 55 ℃,microwave power 540 W,microwave time 76 s,ethanol concentration 60%,extraction temperature 55 ℃,extraction time 1.0 h,material/liquid ratio 1:15 g/mL. Under this conditions,the extraction yield of procyanidins was 14.68 mg/g,at the same time,procyanidins were extracted by ultrasonic-microwave assisted was significantly higher than that of ultrasonic extraction and microwave extraction(P<0.05). This study can provide a theoretical reference for the comprehensive utilization of hop residue.