18A-17 |
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E. ADU-KWARTENG1, G. S. Ayernor2, E. O. Sakyi-Dawson1, V. D. Truong3, F. F. Shih4, and K. W. Daigle4. (1) Nutrition and Food Science Dept., Univ. of Ghana, P. O. Box LG 134, Legon, Accra, Ghana, (2) Nutrition and Food Science Dept., Univ. of Ghana, P. O. Box LG 134, Legon, Accra, Ghana, (3) USDA-ARS, SAA Food Science Research Unit, Dept. of Food Science, Box 7624, North Carolina State Univ., Raleigh, NC 27695, (4) Food Processing and Sensory Quality, Southern Regional Research Center, 1100 Robert E Lee Blvd, New Orleans, LA 70124 Sweetpotato, a nutritious and fast-growing crop, is also an important source of starch in some parts of Asia and Africa. Selection of sweetpotato cultivars with high dry matter and high starch contents and assessment of cultural practices affecting starch characteristics are important in commercial production of sweetpotato starches. The objective of this study was to characterize the physicochemical properties of sweetpotato starches from selected high dry matter cultivars as affected by harvest age. Starches were extracted from the roots of 4 sweetpotato cultivars harvested at 3, 4, and 5 months after planting (MAP) over 2 growing seasons. Amylose content was determined by the concavalin A precipitation method, pasting properties by rapid visco amylography (RVA), thermal properties by differential scanning calorimetry (DSC), particle size analysis by centrifugal method and granule morphology by scanning electron microscopy (SEM). Dry matter contents (30.3 to 47.0%) were generally higher at 4MAP. Extractable starch (10.4 to 21.0%, f.w.b.) decreased with increasing harvest age in two of the cultivars, but varied inconsistently in the other two. Amylose contents ranged from 14.0 to 18.4%. For both growing seasons, amylose levels significantly correlated with RVA peak viscosity (r >0.90) except one variety (r=0.57). Differences in RVA viscosity breakdown between harvest ages in the first season were significant (p <0.05). Granule size distribution ranged from 2-30 to 4-45 microns; SEM revealed surface markings on isolated granules for only 3MAP starches, but in the ‘Mogamba' cultivar markings were consistent across harvest ages. DSC onset and peak temperatures decreased with increasing harvest age for all four cultivars in the second season, but varied inconsistently in the first season. The obtained results would be useful to breeders, growers, and processors in their efforts in improving the efficiency of starch production, as well as tailoring specific functional properties of sweetpotato starch.
Session 18A, Carbohydrate: General
2005 IFT Annual Meeting, July 15-20 - New Orleans, Louisiana |