Physicochemical properties of cross linked acha (digitaria exilis) starch with citric acid

S. Isah, A. A. Oshodi and V. N. Atasie

Abstract

Acha (Digitaria exilis) starch was isolated and crosslinked using citric acid. Physicochemical properties including solubility, water and oil absorption capacities, bulk density, foam capacity, pasting viscosity and granule morphology were determined. Decrease in these properties, except for the emulsion capacity (from 36 to 38%) and least gelation concentration (LGC) which increased from 6% to 8% were observed with modified derivative. General decline was observed
with water absorption capacity (488% to 465%); oil absorption capacity (122 to 116%); pH of starch slurry (6.85 to 6.45); bulk density (0.5 to 0.41g/ml) and foam capacity (4.0 to 3.0%).The starch granule morphology was investigated using scanning electron microscopy (SEM). Cross linking may not have affected the shape but appearance and structural arrangements of the starch granules differ upon modification. The starch granules retain its polygonal shape and the granule size ranges between 6um to 8.57 um. The infrared spectra of native acha starch and chemically modified derivative shown similar peaks, except for the additional peak in the cross-linked sample at 1614 cm-1 indicating the carbonyl bands stretching vibrations. Starch utilization as a food or feed relates to its physical and chemical properties. Cross linking altered these functional characteristics. Thus cross linking of Acha starch may find potential applications as good emulsifying agents, pharmaceutical excipients, disintegrants and drug carrier formulation.