Dong Huaqun;Yuehua Wang;Dong HuaQiang;Gao Saiwe

Department of Food Science,Foshan University,Dali,Nanhai,Foshan,Guangdong 528231,China;Department of Food Science,Foshan University,Dali,Nanhai,Foshan,Guangdong 528231,Chin

melanin;prurients;seed coat;alkaline extraction;acid precipitation;assiste

[Objective] To research the extraction technology of melanin from the episperm of Mucuna prurients(L.) by microwave-assisted alkaline extraction and acid precipitation.[Method] Melanin was extracted from the seed coat of M.prurients by the method of microwave-assisted alkaline extraction-acid precipitation and the method of alkaline extraction-acid precipitation.Content of melanin in M.prurients was detected by UV spectrophotometry.[Result] The content of melanin in M.prurients seed coat was 2.41%.The optimal conditions for alkaline extraction-acid precipitation were 1.0 mol/L NaOH solution,1:20 g/ml solid-liquid ratio,4-6 h extraction time,and pH=2 for the precipitation of melanin.Under these conditions,the yield of melanin crude extracts was(91.2±2.0)%,and its purity reached(36.5±2.1)%.In addition,the optimal technology of microwave-assisted alkaline extraction-acid precipitation was as follows:in accordance with the ratio of solid to liquid 1:20 g/ml,the seed coat and 1.0 mol/L NaOH solution were together exposed to high power ultrasonic for 25 min,with which the maximal yield of melanin was obtained,that is to say,the yield of melanin crude extracts was(95.3±1.5)%,and its purity reached(37.4±1.5)%.[Conclusion] The seed coat of M.prurients was rich in melanin,which deserved further research and development.Microwave assistance could significantly enhance the extraction rate of the crude extracts of melanin and greatly shortened extraction time remarkably.