Detoxification of velvet bean (Mucuna pruriens) by water extraction of L-dopa
2003
Teixeira, A.A. | Rich, E.C.
Water extraction studies were carried out on velvet (Mucuna) beans to determine extraction rate of L-dopa as a function of bean particle size, temperature, and pH. Samples from which L-dopa had been successfully extracted were also assayed for total protein content to determine associated protein loss. Extraction with room temperature tap water was feasible only with the smallest particle size studied (1 mm). At this size, a safe level (0.1%) could be reached within approximately 55 h (2.5 days) of soaking in a minimum of 40/1 parts water/bean. Extraction rates increased dramatically with increased water temperature, allowing safe levels to be reached within 13 h at 40 degrees C and 3 h at 66 degrees C, suggesting, only 40 min would be required in boiling water. Extraction rates increased further with decreasing pH at any temperature. Acidifying water at room temperature to pH 3 allowed extraction to safe levels in less than 8 h. However, increasing water pH into the alkaline range appeared to induce chemical conversion of L-dopa to melanin. No significant loss of protein was found in any of the samples assayed. It appeared that optimum conditions for water extraction of L-dopa from Mucuna bean are similar to those required for brewing of coffee. Beans must first be ground to small particle size and then extracted with hot water.
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