Physicochemical, thermal, morphological and pasting properties of starches from some Indian black gram (Phaseolus mungo L.) cultivars

The starches separated from thirteen different black gram cultivars were investigated for physicochemical, thermal, morphological and pasting properties. Amylose content, swelling power, solubility and water binding capacity of starches ranged between 30.2-34.6%, 16.0-22.3 g/g, 14.8-17.3% and 73.5-84.5%, respectively. The diameter of starch granules, measured using a laser-light scattering particle-size analyzer, varied from 12.8 to 14.3 mum in all black gram starches. The shape of starch granules varied from oval to elliptical. The transition temperatures (T-o, T-p and T-c) and enthalpy of gelatinization (DeltaH(gel)) determined using differential scanning calorimetry, ranged between 66.1-71.3, 71.0-76.2, 75.9-80.4 degreesC and 6.7-9.4 J/g, respectively. Pasting properties of starches measured using the Rapid Visco Analyser (RVA) also differed significantly. Pasting temperature, peak viscosity, trough, breakdown, final viscosity and setback were between 75.8-80.3 degreesC, 422-514, 180-311, 134-212, 400-439 and 102-151 Rapid Visco Units (RVU), respectively. Turbidity values of gelatinized starch pastes increased during refrigerated storage. The relationships between different properties were also determined using Pearson correlation coefficients. Amylose content showed a positive correlation with swelling power, turbidity and granule diameter. Swelling power showed a negative correlation with solubility and setback. T-o, T-p and T-c showed positive correlation with turbidity, pasting temperature and were negatively correlated to peak and breakdown viscosity.