Comparative analyses of functional, pasting and morphological characteristics of native and modified tigernut starches with their blends

Abstract

The effect of some physical and chemical treatments on the functional and pasting characteristics of native tigernut starch (TNNS), native sweet potato starch (SPNS) and blends of tigernut-sweet potato starch were studied. Native tigernut and sweet potato starches were subjected to physical (annealing and heat-moisture) and chemical (acetylation) modifications and compared to tigernut (T)-sweet potato (S) starches blends (T75:S25, T50:S50, T25:S75). Only heat-moisture treatment (THMT) significantly (p ≤ 0.05) increased water absorption capacity of the TNNS while only acetylation significantly (p ≤ 0.05) increased the oil absorption capacity of the native tigernut starch. The bulk density was significantly (p ≤ 0.05) reduced by annealing and acetylation. In addition, TNAS, mixture of blends and SPNS had higher swelling capacity than TNNS. The final and peak viscosities of TNNS, SPNS and all the starch blends were between (217–280 RVU) and (214–395.3 RVU) respectively with SPNS having the highest values, followed by T75:S25 (75% tigernut starch: 25% sweet potato starch) and TNNS in that order. TNNS also had the highest setback viscosity. Samples THMT, TANN and TNAS significantly (p ≤ 0.05) reduced the breakdown viscosity and the pasting temperature. The scanning electron micrograph showed that the native and modified starches of tigernut were similar to those of other starches. Overall, the results showed that many of the pasting characteristics of TNNS were comparable to SPNS, while SPNS had with better functional characteristics.

Keywords

• functional
• modification
• pasting characteristics
• scanning electron micrograph
• starch
• sweet potato
• tigernut