Wet-fractionation of Phaseolus lunatus seeds: partial characterization of starch and protein

The optimum extraction conditions for integral use of Phaseolus lunatus seed, in alkaline medium, are 1:6 (w/v) flour:water ratio, pH 11 and a 1 h extraction time. Three main fractions were produced under these conditions: starch; protein isolate and fibrous residue byproduct. The yield is 288.4 g kg^-1 starch, 188.2 g kg^-1 protein isolate and the remaining quantity, fibrous residue. The starch has 98.4% purity, a 75 °C gelatinization temperature and high syneresis even at high concentrations. It also has high viscosity, good stability and middle retrogradation during the heating-cooling cycle. The protein isolate contains 711.3 g kg^-1 protein as well as 75.5 g lysine kg^-1 protein, 10.1 g methionine kg-1 protein and 12.2 g tryptophan kg^-1 protein. Its in vitro digestibility is 79% with a 2.5 cPER. The fibrous residue contains 63 g kg^-1 of protein, 328.4 g kg^-1 of crude fiber and 567.3 g kg^-1 of NFE.