Isolation and Characterization of Lima Bean (Phaseolus Lunatus) Starch

Starch from large lima beans (Phaseolus lunatus) was isolated and some of the important characteristics determined. The yield of starch was 22% on a whole seed basis. The shape of the starch granules was round to oval to elliptical, with granules 15–36 μm diameter. Scanning electron micrographs revealed presence of smooth surfaces. Gelatinization temperature range was 70–75–80°C and amylose content was 34.5%. The starch exhibited high single stage swelling and moderate solubility in water. The x-ray diffraction pattern was of the C-type. The viscoamylographic examination on starch paste (6%, w/v) showed the absence of a peak viscosity, a high 95°C viscosity (700 BU) and a breakdown in consistency (60 BU) during the 95°C holding cycle. Scanning electron microscopy showed that native starch granules were very resistant to attack by porcine pancreatic α-amylase. However, defatting slightly increased the extent of hydrolysis. The gel showed poor stability towards refrigerated storage and freeze-thaw cycling. The starch granules were highly resistant to acidic hydrolysis.