Amylolytic Activity in Selected Sweetpotato (Ipomoea batatas Lam) Varieties during Development and in Storage

Agnes Nabubuya, Agnes Namutebi, Yusuf Byaruhanga, Judith Narvhus, Yngve Stenstrøm, Trude Wicklund

Department of Chemistry, Biotechnology and Food Science, Norwegian University of Life Sciences, Aas, Norway.
Department of Food Technology and Nutrition, Makerere University, Kampala, Uganda.

DOI: 10.4236/fns.2012.35090                

Abstract

Sweetpotato varieties (five) were investigated for changes in α- and β-amylase activities during root development and on subjection of harvested roots to different postharvest handling and storage conditions. Changes in α- and β-amylase activities in development were monitored from 10 weeks after planting. At physiological maturity, sweetpotato roots were harvested and subjected to various conditions: freshly harvested roots and cured roots (spread under the sun for four days at 29℃ - 31℃ and 63% - 65% relative humidity), stored at ambient conditions (23℃ - 26℃ and 70% - 80% relative humidity) and in a semi-underground pit (19℃ - 21℃ and 90% - 95% relative humidity). Generally α- and β-amylase activities increased during development with NASPOT 9 and 10 consistently registering the highest activities and NASPOT 1 the lowest activity. Generally, maximum α-amylase activities were achieved at week 3 in ambient stores for NASPOT 9 and NASPOT 10 at 0.930 and 0.897 CU/g, respectively. Maximum β-amylase activity was achieved in ambient stores at week 3 and 4 for fresh and cured NASPOT 9 at 806 and 782 BU/g, respectively. Generally, curing and storing sweetpotatoes in ambient conditions registered the highest amylase activity. Maximum α- and β-amylase activities were registered at 67℃ - 68℃ and 58℃ - 60℃, respectively. These findings provide information for controlled modification of amylase activities of these sweetpotato varieties for product development efforts and monitoring the shelf life of the roots during storage.

Keywords

Sweetpotato; α-Amylase; β-Amylase; Development; Postharvest Handling; Storage

Conflicts of Interest

The authors declare no conflicts of interest.

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