Comparison of Polyphenol Extraction Methods from Yam Peel and its Antioxidant Activities
Objective:This study compared the extraction process of yam peel polyphenols(YPP),and evaluated the in vitro antioxidant activity.Methods:Ultrasonic-assisted enzymatic hydrolysis and microwave-assisted enzymatic hydrolysis extraction process of YPP were optimized by single factor tests and orthogonal tests,the antioxidant capacity of YPP extracts obtained by two methods was compared.Results:The results showed that ultrasound-assisted enzymatic hydrolysis was superior to microwave-assisted enzymatic hydrolysis,optimal extraction conditions of ultrasound-assisted enzymatic hydrolysis were as follows:solid-liquid ratio 1∶15 g/mL,enzymatic temperature 60 ℃,ultrasonic time 30 min,ultrasonic power 300 W,enzyme hydrolysis concentration 20 mg/g,ethanol concentration 75％,pH5,The YPP extraction yield was 2.3865 mg/g,which was 1.33 times higher than that of the microwave-assisted enzymatic hydrolysis method and 2.34 times higher than the traditional ethanol static extraction method.Scanning electron microscopy(SEM)of the extracted residues showed that the ultrasonic-assisted enzymatic method caused more significant structural damage compared to the traditional static extraction and microwave-assisted enzymatic hydrolysis methods,facilitating better YPP release.In vitro antioxidant studies have shown,the removal rates of 1,1-diphenyl-2-picrylhydrazyl(DPPH)radical and 2,2'-azino-bis(3-ethylbenzthiazoline-6-sulfonic acid)(ABTS)radical cation,hydroxyl and superoxide anion radical of YPP extracted by ultrasound-assisted enzymatic hydrolysis were significantly higher than those obtained by microwave-assisted enzymatic hydrolysis method.Conclusion:The ultrasonic-assisted enzymatic hydrolysis method yielded a higher extraction rate of YPP,and the extracts exhibited strong antioxidant activity,making it a superior extraction method for YPP.
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