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The native starches isolated from pigeon pea (Cajanus cajan L.), lima bean (Phaseolus lunatus L.) and jack bean (Canavalia ensiformis) were pregelatinized at 50 and 55 oC. The native starches and their derivatives were studied for their flow and thermal behaviours. Both the native and pregelatinized starches possessed pseudoplastic flow behaviours (n<1). Flow behaviour indices, n of the starch samples ranged from 0.62 to 0.86, consistency coefficient (Pa.sn), K, from 0.01 to 0.83, and yield stresses (Pa), σo, from 0.18 to 2.86. The native starches possess higher shear viscosities than their pregelatinized derivatives, except for PPS. The values of the gelatinization temperatures were higher than the temperatures of pregelatinization of the native starches. After storage for 7 days at 4 oC, the values of transition temperatures of the starches were lowered, having undergone retrogradation. However, the native starch granules were more homogeneously distributed than their pregelatinized derivatives. These starches could be possible alternative sources of starch in meeting its ever-increasing demand in food and non-food applications such as bakery products, desserts, baby formulations and disintegrants for tablets.
Keywords: Pregelatinized starch, flow behaviour, thermal properties