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MATERIAL AND COMPRESSION PROPERTIES OF NATIVE AND MODIFIED PLANTAIN STARCHES

JOHN O. AYORINDE^1*, MICHEAL A. ODENIYI¹, YINKA J. OYENIYI²

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Native forms of starch lack certain properties such as viscosity and stability and this limits its use in pharmaceutical formulations. This limitation can be improved by physical and chemical modifications. Hence comparative evaluation of the properties of native and modified forms of plantain (Musa paradisiaca) starch was done with a view to assessing their usage in pharmaceutical formulations. Starch was modified by freeze drying and microwave irradiation. Properties of native (NAT) and modified starches were determined by measuring their projected mean diameter, Heywood constant and specific surface area. Densities and compressibility index of the starches were determined by standard methods. Volume reduction parameters were obtained using Kawakita and Gurnham equations. The angle of internal flow was evaluated by measuring porosity of the starch with increasing number of taps. Other physicochemical properties were determined using viscosity measurement and Fourier Transform Infrared (FTIR) spectrometry. There were differences in the properties of the native (NAT), microwave dried (MCD) and freeze dried (FRD) starches. MCD starch had the smallest mean granule diameter and the largest specific surface area while NAT starch had the largest mean granule diameter with the smallest surface area. The rank order in the bulk density and packing fraction of the starch was FRD > MCD > NAT and NAT > MCD > FRD respectively. The rank order for the angle of internal flow (θ) which is inversely related to powder flow was NAT > MCD > FRD (p < 0.05). The starch became more viscous after microwave drying than after freeze drying modification. FTIR spectra revealed that microwave and freeze drying had effects on the starch properties, however, there was no effect on basic chemical structure. MCD starch had higher maximum volume reduction with particles packing more, under tapping than FRD and NAT starches. Similar trend of volume reduction was obtained with both Kawakita and Gurnham equations. Microwave irradiation improved starch viscosity while freeze drying imparted closer packing of starch particles and better flow properties. The choice of modification method should be determined by the intended dosage form in which plantain starch will be used.