Physicochemical Properties of Native and Modified Selected Tropical Root and Tuber Starches
D. I. Ifediba *
Federal University of Technology, Owerri, Imo State, Nigeria.
C. I. Owuamanam
Federal University of Technology, Owerri, Imo State, Nigeria.
G. C. Omeire
Federal University of Technology, Owerri, Imo State, Nigeria.
A. A. Nwakudu
Federal University of Technology, Owerri, Imo State, Nigeria.
*Author to whom correspondence should be addressed.
Abstract
Three tropical root and tuber crops, namely cassava (Manihot esculenta TME 419), white Guinea yam (Dioscorea rotundata Poir.) and sweet potato (Ipomoea batatas Lam.), were evaluated as starch sources and subjected to chemical modification. Native starch yields were 23.82%, 18.65% and 21.74% on a dry basis for cassava, sweet potato and white Guinea yam, respectively. The extracted starches were modified by acetylation, acid hydrolysis and oxidation, and were assessed for amylose and amylopectin contents, particle size, colour characteristics and flow-related properties, including Hausner’s ratio, bulk ratio, compressibility index, porosity, angle of repose and coefficient of static friction. Significant differences were observed among the native and modified starch samples for most measured parameters. Acetylation produced the most notable improvement in particle size, lightness and whiteness, while oxidation resulted in the highest amylose content, particularly in cassava starch. Acid hydrolysis showed favourable effects on selected flow properties, especially in yam starch, which had the lowest Hausner’s ratio and highest bulk ratio. The findings indicate that chemical modification altered the physicochemical and flow behaviour of the starches in ways that depended on botanical origin and treatment type. These results provide useful baseline information for further application-specific evaluation of modified tropical root and tuber starches.
Keywords: Starch modification, cassava starch, sweet potato starch, white Guinea yam starch, acetylation, acid hydrolysis, oxidation, amylose, amylopectin, powder flow properties, colour profile.