Physicochemical characterization of mung bean starch

Abstract

Starch from mung bean (Vigna radiata) was isolated and some of the important characteristics determined. The yield of starch was 31.1% on a whole-seed basis. The shape of the starch granule was oval to round to bean shaped, with granules 7–26 μm in diameter. Scanning electron micrographs revealed the presence of smooth surfaces. The gelatinization temperature range was 58–67–82°C and the enthalpy of gelatinization was 18.5 J/g. The total amylose content was 45.3%, of which 12.1% was complexed by native lipids. The X-ray diffraction pattern was of the ‘C’ type and the X-ray intensities were much stronger than in other legume starches. The starch exhibited a high swelling factor ( 43.6 at 95°C) in water. The viscoamylographic examination of the starch paste (6% w/v) showed the absence of a peak viscosity, a low 95°C viscosity [200 Brabender units (BU)], an increase in consistency ( 140 BU) during the holding cycle at 95°C and a set-back of 220 BU. Native granules were readily hydrolyzed by porcine pancreatic α-amylase (76.4% in 72 h). Retrogradation of mung bean starch (as measured by changes in syneresis, gel strength, enthalpy and X-ray diffraction intensities) appeared to be more severe than in other legume starches.