Changes in rheological properties and amylase activities of trifoliate yam, Dioscorea dumetorum, starch after harvest

Abstract

Changes in rheological properties and amylase activities occurring in trifoliate yam, Dioscorea dumetorum, starch after harvest were investigated. Trifoliate yam tubers were harvested and stored under tropical ambient (28°C) and cold room conditions (4°C) for 12, 24 and 36 h. The D. dumetorum starches were extracted from the tubers under study and samples were evaluated for changes in their rheological properties (paste characteristics) during storage and to study the action of amylases on D. dumetorum starch after harvesting. The post-harvest activities of α and β-amylases were also studied to evaluate their rate of action on D. dumetorum starch. Storage caused decreases in the rheological properties (paste characteristics) of the tubers within 36 h of harvest. Similarly, α and β-amylase activities in the tubers more than doubled within 24 h after harvesting. Blanching, however, effectively decreased the action of amylases on D. dumetorum starch during storage, with subsequential increase in the paste viscosities of the stored tubers. Low temperature storage of the tubers also slowed down the rates of decrease in both the rheological properties and amylase activities during the 36-h storage period. © 2002 Published by Elsevier Science Ltd.