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 by-product. 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 75degreesC 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 c-PER. 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. (C) 2004 Society of Chemical Industry.