Microwave Assisted Extraction of Anthocyanins from Red Cabbage and Evaluation of Freeze Dried Extract

Lim, Grace Kar Yee (2019) Microwave Assisted Extraction of Anthocyanins from Red Cabbage and Evaluation of Freeze Dried Extract. Final Year Project (Bachelor), Tunku Abdul Rahman University College.

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Abstract

Anthocyanins are one of the phenolic compounds that often used as a natural food colourant which also possess unique antioxidant effect. An efficient extraction method is needed to increase the quality of the extracted anthocyanins while downstream preservation is important to maintain its stability. This research works on the investigation of microwave assisted extraction of anthocyanins from red cabbage and evaluation the properties of freeze dried red cabbage extract powder. The effects on microwave power from 80 to 500 W and extraction time from 30 to 120 seconds on yield, total anthocyanins concentration and colours of red cabbage were investigated. The evaluation of freeze dried extract on yield, total anthocyanins concentration, physico-chemical properties, 2, 2,-diphenyl-1-picrylhydrazyl (DPPH) free radical scavenging activity and total phenolic content (TPC) of freeze dried powder was performed. The physico-chemical properties of freeze dried powder were conducted on colour, pH, solubility, water activity, bulk density and moisture content. Increase in both microwave power and extraction time, both increased the total anthocyanins concentration. The optimized microwave assisted extraction of red cabbage extracts was determined at 400 W and 120 seconds with significantly highest total anthocyanins concentration at 75.37 mg/L with p < 0.05 and a low colour difference at 2.00. In comparison between freeze dried red cabbage extract powder obtained after treated with control (without treatment), conventional extraction (45 °C, 120 seconds) and microwave assisted extraction utilizing the optimized parameters (400 W, 120 seconds), the freeze dried red cabbage extract powder enhanced by microwave showed significantly highest total anthocyanins concentration at 41.75 mg/L, antioxidant activity in DPPH (2.81mg AAE/g) and TPC (7.38 mg GAE/g) with p < 0.05. Microwave is potential to enhance the extraction of anthocyanins from red cabbage in producing natural food colourant.