Tropical Sources of Starches

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3. Other starches

  1. Pulses

    1. Chick Pea, Cow Pea and Horse gram

      The starches from these have been studied by El Faki et al, 93. The starch granules had varying sizes, 8-54um for chick pea, 4-39um for cow pea and 15-85um for horsegram starches. The shape varies from large oval shape to small spherical and with smooth surfaces. Chick pea and horsegram starches had B XRD pattern while it was A for cow pea. The amylose content for the starches were in the range 32-34%. The gelatinisation temperature ranged from 60-75°C for chick and cowpea while it was 71-80°C for horse gram. The cow pea and horsegram starches had much higher viscosity compared to chick pea, the vales being around 1500 BU for horse gram and cowpea compared to 600 for chick pea at 10% level.

    2. Winged bean

      Umadevi and Wankhede 94 have studied the starch properties of winged bean starch. The starch granules are of two types : oval (25-36um) and round (10-12um). Under polarised light, they show strong centric crosses. The lipid content is 0.95% . The amylose content obtained by fractionation is 36% similar to other legume starches . The gelatinisation temperature ranged from 61-70°C . The swelling power increases with temperature reaching 18.5 at 100°C, the solubility being 15% at this temperature. The digestibility of the native starch by alpha amylase was very low (15%), but increased to 40% on gelatinisation. However glucoamylsase completely hydrolysed gelatinised starch.

    3. Baby Lima Bean

      The starch granules are oval in shape and size ranging from 10-52um, average being 18um. The starch has a fat content of 0.54% while amylose content is 32.7% similar to other bean starches. The gelatinisation temperature using > DSC was 75-87°C which can be considered high. The gel strength of the starch paste is quite high. The swelling power increased above 70°C and reached 19.9g/g at 90°C . while the solubility was 12% at 900C. The Brabender viscosity values were as follows: Peak Viscosity 668, VH 612, VC 850 indicating only low breakdown and setback. The starch showed high synerisis explained on basis of high amylose content in the starch. The starch properties show that it can be incorporated into baked and canned foods due to higher gelatinisation temperature and water absorption capacity, but use as thickening and gelling agent in frozen or refrigerated foods is limited due to high synerisis.95

    4. Velvet bean

      The starch granules are oval having size range of 15-30um. The fat content is 0.4% while amylose content is quite high at 39%. Gelatinisation temperature is 70-80°C microscopically. DSC data indicate the Tpeak at 75°C . The gel strength is good. The selling power is 17g/g at 90C while solubility is 15%. The Brabender viscosity did not show any maximum and viscosity values are lower compared to lima bean. Bentancur et al 96 conclude that the starch is good for products that require cooking at high temperatures during manufacture since it maintains good consistency during processing.

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