Changes in cell wall constituents and mechanical properties during post-harvest hardening of trifoliate yam Dioscorea dumetorum (Kunth) pax tubers

In an attempt to investigate the changes leading to the rapid post-harvest hardening of the white cultivars of Dioscorea dumetorum tubers, alterations in the plant cell wall constituents and mechanical properties of the tubers were monitored. A 4 x 2 factorial experiment with storage time (0, 24, 48 and 72 h) and storage conditions [cold room (4 C, 85-100% RH) and tropical ambient (28 degreesC, 62-100% RH)] as variables were performed. Harvested tubers were stored for 24, 48 and 72 h under 4 and 28 degreesC. Changes in mechanical properties, acid and neutral detergent fibres, lignin, cellulose and hemicellulose contents were monitored. Mechanical properties comprising peak force (hardness) and curve areas (adhesiveness) increased rapidly from 1203.0-5816.5 g and 12.4214-29.2612 g, respectively, during the 72 h of storage at ambient conditions. Similarly, all the plant cell wall constituents evaluated increased to significant levels (P less than or equal to 0.05) within the period. Peak force (hardness) values correlated positively (r=0.78290.9367, P less than or equal to 0.05) with all the cell wall constituents investigated. Hardening of D. dumetorurn was characterized by increased fibre levels and cell walls of the tuber. However, the rate of cell wall thickening varies with the storage time and storage temperature. (C) 2002 Elsevier Science Ltd. All rights reserved.