Comparative Evaluation of Some Properties of Native and Oxidized Cassava, Yam and Rice Starches
The study was designed to produce native starches from cassava, yam and rice, and to modify a portion of the native starches by oxidation and compare their properties. The modification process was carried out by treating the native starches with food grade sodium hypochlorite (NaOCl). The proximate, swelling index and pasting properties of native and oxidized starches were analyzed using standard methods and the mean values compared statistically. Some of the oxidized starches had varying degrees of improvement in their properties. The ash content of the oxidized starches was low when compared with the native starches. The fiber content was increased as the oxidized samples had significantly (p < 0.05) higher values than their native counterparts. The swelling index trend shows that oxidized rice starch had the highest peak while the native starches presented the lowest deep. Oxidized rice starch had the highest fiber while the native cassava starch had the least. Native rice starch had the highest peak viscosity (4922 cP) while the oxidized rice had the lowest peak viscosity (1223 cP). Sodium hypochlorite treatment improved the setback viscosity of the oxidized starches, which indicates that oxidized yam and cassava starches with high values acquired greater integrity to withstand retro-gradation. Thus, when the oxidized cassava and yam starches are used in food formulation, they might be able to withstand syneresis or weeping during freeze-thaw cycles. There is the need to explore more about starches from tropical roots and tuber crops and application of a variety of modifications in order to unlock their potentials for industrial applications.
Keywords: Native starch, hypochlorite, oxidized starch, swelling index, setback viscosity.