Comparative analyses of functional, pasting andudmorphological characteristics of native andudmodified tigernut starches with their blends

摘要

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