Abstract

Physicochemical properties of starches of two popular Nigerian sweet potato (NSP1 and 2) cultivars were studied using those from Chinese sweet potato (CSP), cassava (CC) and potato (CP) widely used for starch production, as references. Moisture, ash, protein, and phosphorus contents of the starches varied from 4.34 to 9.48%, 0.26 to 0.31%, 0.05 to 0.42% and 0.018 to 0.995%, respectively with NSP starches showing significantly (p < 0.05) higher protein and lower ash content. The starches differed in amylose content, granule shapes, mean granule sizes, particle size distribution, enzyme digestibility; swelling power and solubility pattern. Higher retrogradation tendency was observed in NSP1 and CP starch pastes compared to those of CSP and NSP2. Thermal properties varied in the various starches. NSP1 and 2 showed higher gelatinization temperatures (73.17, 71.64°C), lower peak viscosities (2269, 2295 cP) and lower stability ratios (0.49, 0.54), respectively compared to the Chinese starches. Mean granule size and phosphorus content of the starches had substantial effect on their pasting properties. However, variability observed in the properties of the various starches further projected their useful and comparative potentials in food and non-food applications.

Key words: Sweet potato, starch, pasting properties, thermal properties, retrogradation, digestibility.