Hard-to-cook defect in trifoliate yam Dioscorea dumetorum tubers after harvest

In an attempt to study the hard-to-cook defect in Dioscorea dumetorum tubers after harvest, yellow cultivars of trifoliate yam tubers were stored under range of temperatures (15, 30, 45 °C ) and relative humidity (59%, 75%, 86% RH), and then soaked and cooked in distilled water or 5% (w/v) aqueous solution of Na2 EDTA. The hard-to-cook defect was separated into reversible and irreversible components. Results of phytate and lignin analysis led to the conclusion that these components reflect the pectin-phytate mechanism or reversible hardening and the lignification mechanism or irreversible hardening. Modeling of the hardening process indicated that the rate of reversible and irreversible reaction was dependent on storage conditions, however, irreversible hardening rate was generally faster than reversible hardening and then represented the major component of D. dumetorum tubers hardening.