Microwave-assisted extraction of phenolics from bean (Phaseolus vulgaris L.)

Phenolic phytochemicals are associated with many health benefits, and it would be useful to develop improved methods for their extraction from bean. In this work, we showed that microwave-assisted extraction was an effective method. Eight bean types important in the Northarvest region of North America, which includes North Dakota and Minnesota, were chosen for this study. Four temperatures (25, 50, 100 and 150 °C) and three solvents (water, 50% ethanol in water and 100% ethanol) were investigated. As expected, colored beans contained higher concentrations of extractable phenolics, and in most cases the concentration of phenolics was much higher in the hull (testa) than in the cotyledon. Extraction efficiency was superior at higher extraction temperatures. The most effective extraction was achieved at a temperature of 150 °C using 50% ethanol. Total phenolics contents determined by microwave-assisted extraction with water at 100 °C were two to three times those determined by conventional extraction with water at the same temperature.