Rheological and structural properties of modified starches from the young shoots of Borassus aethiopium

• Starch from the young shoots of Borasus aethiopium was chemically modified.
• The native starch and derivatives exhibited viscoelastic behaviour.
• The gelatinization of starch was retained in the derivatives.
• Syneresis experienced by native starch was inhibited by acetylation.
• Some derivatives may be preferable to native starch in liquid dosage formulations.

Starch from the young shoots of Borassus aethiopium was chemically modified by acetylation, oxidation and a combination of acetylation and oxidation. The modification was confirmed by Fourier Transform Infra-Red (FTIR) and the crystal structure by X-Ray Diffractometry (XRD). The effect of the chemical modification on starch syneresis was evaluated while the effects on rheological properties of 10%w/v dispersion of the starches or their gels were evaluated on Bohlin Gemini rheometer. The FT-IR confirmed the presence of acetyl groups at 1720 cm−1 with associated increase in intensity of the peak at 1228 cm−1, while the oxidized showed a slight increase in intensity of the peak at 1380 cm−1. All the starch samples exhibited a crystalline region with three prominent XRD peaks, centred on 2ϴ = 15.3, 17.2 and 23.1°. Heating scan of all the starch samples showed transitions due to gelatinization and the temperature at peak elastic modulus (TG′) were 76.9 ± 0.14, 67.2 ± 0.14, 75.4 ± 0.64 and 71.5 ± 0.14 for the native starch, acetylated starch, oxidized starch and acetylated/oxidized starch respectively. The native starch undergoes syneresis which was reduced by oxidation, whereas the acetylated starches did not undergo syneresis. The present study showed that the modified products did not exhibit superior rheological properties when compared to the native starch but displayed the advantage of reducing or totally preventing syneresis of the native starch upon acetylation.

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