Structure and physicochemical properties of starches from kidney bean seeds at immature, premature and mature stages of development

Starches from kidney bean (Phaseolus vulgaris L. cv. Toramame) seeds at the immature, premature, mature stages of development were examined. The starch content increased from 94, 219 to 265 mg per seed. Starches showed the Ca-crystalline type composed of small (<5 μm) and large (10–35 μm) granules, with the large granules largely increasing with maturity. The amylose content increased from 21, 26 to 27%, and rapid viscograms and DSC thermograms suggested that the mature-stage starch was gelatinized with ease. The amylose increased in size from DPn 820, 1000 to 1080 and a number of chains per molecule (NC) from 3.3, 4.2 to 4.5. The branched amylose was a minor component (11–18% by mole) with NC 20–22. The amylopectin was similar in CL (23), β-amylolysis limit (59%), and chain-length distribution, but reduced in size (DPn 17,100–5270) and increased in content of phosphorus (114–174 ppm) with an increase in the amount of phosphorus linked to C-6 of the glucose residue (8–66%).