Association between Fruit Characteristics and Postharvest Stability of Different Pumpkin (Cucurbita) Species

This study aimed at understanding peel and flesh characteristics of Cucurbita maxima Duchesne subsp maxima, Cucurbita pepo L var. fastigata and Cucurbita moschata Decne pumpkin varieties and how the fruit characteristics relate to its postharvest stability. Mature fruits were stored at ambient conditions (28oC and 78% Relative humidity) for eight months. Cell microscopic structure, intercellular space size, sugars, starch, cellulose, hemicellulose, lignin, degree of esterification of pectin, polygalacturonase activity, and cumulative moisture lost were determined monthly. Sucrose, starch, cellulose and hemicellulose content and degree of esterification of pectin of different varieties decreased with storage. Glucose and fructose content increased to a maximum and then reduced. Polygalacturonase activity and lignin generally increased with storage time. Size of intercellular spaces, and cumulative moisture lost from both flesh and peel increased with storage. Sucrose breakdown was key during 0 to 3 months, while moisture loss was important at 4 months of storage. Polygalacturonase activity became paramount from 7th month of storage. Postharvest stability of pumpkins is determined by an interplay of factors. The deterministic factor changes with time. Pumpkin varieties with more lignified peel had lower rates of sucrose breakdown and moisture loss and tended to be more stable postharvest. Varieties with low level of hemicellulose had their cell walls degrade early, while deterioration of pumpkins with highly esterified pectin and closely packed cells was delayed.