Quality Characteristics of Native Starch from Selected Improved Varieties of Sweetpotato (Ipomoea batatas)

2017

English

Sweetpotato (Ipomoea batatas L.) is a starchy root crop with a wide range of diversity in physical and compositional characteristics. Links between starch properties and processing characteristics are known to have an impact in utilization. Starches were extracted from six (6) improved varieties of sweetpotato harvested at 3, 4 and 5 months after planting. Starch granule morphologies were characterized at 4 months using Light Microscopy, and starch pasting properties were determined at all harvest times by Rapid Visco Analyzer. Granular shapes were generally heterogeneous and approximate size distributions varied from 2 to 15m to 8 to 40m. peak viscosity ranged from 4077 to 5260 centipoise, pasting temperature ranged from 77.95 to 82.45oC, setback ratio ranged from 1.25 to 1.61 and stability ratio ranged from 0.52 to 0.73. Starches with smaller granules had relatively low peak viscosities and high stability or resistance to breakdown while those with larger granule size ranges had lower setback ratio, indicating less retrogradation and better long-term cold paste stability. The influence of both variety and harvest maturity on all RVA pasting properties were significant at p<0.001. Small starch granule size varieties harvested at 4 and 5 months had the lowest peak viscosities and highest setback ratio; larger granule size varieties harvested at 4 months had the highest peak viscosities and lowest setback ratio. These results are relevant in understanding the processing and utilization quality of the varieties studied, and also in identifying potential niche applications for sweetpotato starch as food ingredients or in other applications.

E. Adu-Kwarteng, I. Oduro, W. O. Ellis, J.K Agbenorhevi