Tannia starch: structural and functional characterisation

Tannia starch (Xanthosoma sagittifolium) is less characterised than other tropical tuber starches. This study analysed the compositional, structural, thermal, and functional characteristics of crude and purified tannia starch to assess the impact of purification. Starches were examined using X-ray diffraction (XRD), proximate and particle size distribution analysis, scanning electron (SEM) and polarised light microscopy (PLM), pasting profile analysis, and differential scanning calorimetry (DSC). Proximate analysis showed minor differences between crude (CS) and purified (PS) starch preparations, indicating that tannia starch is fairly pure even in its crude form. Distinct differences were observed in pasting properties; CS (22% amylose), exhibited lower peak viscosity and setback, reflecting limited swelling and weaker retrogradation, whereas PS (28.5% amylose) displayed higher peak viscosity (2573 cP), greater breakdown, and a higher setback (820 cP), indicative of stronger swelling but reduced shear resistance. Both starch preparations had a mean granule size of ~3 μm, and showed increased particle aggregation following extraction. XRD patterns revealed A-type crystallinity, while PLM indicated the loss of birefringence upon heating. Both starches exhibited similar gelatinisation temperature (~83 °C) as determined by DSC and pasting analysis. In conclusion, native-crystalline CS and PS provide pastes of enhanced viscosity and gel strength for functional applications.