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Extraction and analysis of antioxidant capacity in eight edible beans

Biswas, Atanu, Sutivisedsak, Nongnuch, Cheng, Huai N., Willett, Julious L., Lesch, William C., Tangsrud, Robert R.
Journal of food, agriculture & environment 2012 v.10 no.1 pp. 89
antioxidant activity, antioxidants, beans, beta-carotene, bleaching, cotyledons, ethanol, foods, heat, hulls, microwave treatment, phenolic compounds, solvents, temperature
Beans are known to be a rich source of antioxidants in foods. In this work, we report our preliminary studies of the use of microwave as a fast method for the extraction of antioxidants from beans. Antioxidant capacities of the extracts from cotyledon and hull of eight common beans were determined, using the β-carotene bleaching method. Microwave-assisted extraction was achieved using two solvents, 50:50 ethanol/water or 100% ethanol. For comparison, conventional heat extractions were also done at 100ºC at 50:50 ethanol/water and 100% ethanol. The hull extracts exhibited more antioxidant activity than the cotyledon extracts. In most cases, the extraction with 50:50 ethanol:water tended to produce more antioxidants than extraction with 100% ethanol. The amount of extractables depends strongly on extraction temperature, with 150ºC giving better results. Although there was no correlation between the total phenolic content and antioxidant activity across the eight beans, within the data of each bean type the total phenolic content did correlate with antioxidant activity for most beans. The correlations were strongest for the extraction data on hull using 50:50 ethanol:water as the extraction solvent.