Physical, Chemical and Functional Characterization of a Novel Starch from Dioscorea sagittifolia and its Synergetic Studies with Terminalia mantalys Gum

Abstract

A novel starch extracted from Dioscorea sagittifolia and its composite blends with gum from Terminalia mantalys were studied. The starch/gum blends were prepared in the following ratio: 3.0:0.0, 3.0:0.25, 3.0:0.50, 3.0:0.75 and 3.0:1.0. The proximate and functional properties of the novel starch were determined using standard procedures. The proximate analysis of the starch gave values of 14.37%, 84.63%, 2.30%, 1.92%, 1.34%, 0.56% and 93.88% for moisture, dry matter, crude protein, ash, crude fibre, crude fat and carbohydrate respectively. The energy value was 389.76 Kcal/100 g. The amylose and amylopectin contents of the novel starch were 23.65 and 76.35% respectively. There were significant differences in the solubility index, bulk/particle density, least gelation concentration and foaming capacity of the free starch and its blends while there were no significant differences in their water absorption capacity and swelling power. The peak and trough viscosities ranged from 26.17 (starch/gum ratio of 3.0:0.25) to 246.75 RVU (starch/gum ratio of 3.0:1.0) and 19.00 (starch/gum ratio of 3.0:0.25) to 221.75 RVU (starch/gum ratio of 3.0:1.0) respectively. Final viscosity ranged from 73.25 (starch/gum ratio of 3.0:0.25) to 290.67 RVU (starch/gum ratio of 3.0:1.0) while the pasting temperature and time ranged from 88.05 to 95.00 and 6.87 to 7.0 min, respectively. The morphology of the starch granules (size and shape) was studied with scanning electron microscope (SEM), which revealed cylindrical, rod-like or oblong and oval shaped granules that are symmetrical with smooth surfaces and with lengths between 134 and 179􀀀􀀁m. There were no appreciable change in shapes and sizes of the starch granules after modification with T. mantalys gum. Generally, there were improvements in the functional properties of the starch after modification. The nutritional properties of the novel starch have also been revealed. Keywords: Dioscorea sagittifolia, Terminalia mantalys, Starch, Gum, Functional properties