Management of post harvest ridge blackening of okra (abelmoschus esculentus (l.) moench) pods
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Okra (Hibiscus esculentus) has become a potential non-traditional agricultural export for Uganda since 1993. However, quality is still the biggest constraint and needs to be improved to successfully expand Uganda’s export market. Ridge blackening is the most common quality problem of okra in Uganda. In an effort to manage ridge blackening of okra, three experiments were set up in 2003/2004 to develop a reliable method for determining the severity of ridge blackening on okra pods, to establish the relationship between frequency of handling of pods and severity of ridge blackening and to evaluate field packing as a feasible method for management of the problem. An ordinal rating scale for determination of severity of ridge blackening was developed and its accuracy and precision was compared with the visual estimation scale based on Horsfall-Barratt. Using this scale, seven varieties of okra (“Pure luck”, “Lucky five”, “Greenie”, “Nirali”, “Pusa sawani”, “Clemson Spineless” and “Ever lucky”) were screened for varietal resistance/ tolerance to ridge blackening and two methods of postharvest handling of okra were investigated. Under the conventional (pack-house) method, okra pods were harvested and transported to a pack-house facility where sorting, grading, packing and cooling were carried out, while field packing involved sorting, grading and packing in the field, and transporting of the products to the pack-house cooling facility. The number of times the pods were handled, the severity of ridge blackening, weight loss of pods and microbial load on pods were recorded for the two handling methods. The results of the study showed that the ordinal rating scale was more accurate in measuring ridge blackening of okra at all levels of severity (1-100%) compared to Horsfall-Barratt (1945) visual method which tended to overestimate severity below 25 %. Okra variety significantly (P<0.05) affected the severity of ridge blackening. Variety ‘Pusa sawani” showed the lowest severity while variety ‘Clemson spineless’ and ‘Nirali’ showed horizontal resistance as a high incidence of ridge blackening but low severity. Variety ‘Pure luck’ and ‘Ever lucky’ showed very high severities of ridge blackening figures 3 a. and b). Field packing led to less handling of pods (35 times) compared to conventional packing (48-59 times). This resulted in significantly (P<0.01) lower severity of ridge blackening, lower microbial load and lower rates of weight loss during storage. It is recommended that growers adopt varieties with relatively higher resistance to ridge blackening and minimize the number of times the pods are handled and should consider field packing where applicable.