Μελέτη της επίδρασης διαφόρων παραγόντων που επηρεάζουν την μετασυλλεκτική συμπεριφορά και ποιότητα της μπάμιας (Hibiscus esculentus)

Abstract

In the present study, the postharvest behaviour of small okra pods of cv Boyiatiou was evaluated in relation to the duration of storage, the storage temperature and packing. The main aim was to prolong the length of storage of the pods at good marketable quality. The susceptibility of pods to chilling injury during cold storage was also studied, as well as the effects of nitrogen concentration during cultivation on the postharvest life of the pods. The storage behaviour of the small pods was compared with that of the large-fruiting cv Clemson Spineless. According to the results, okra pods of cv Boyiatiou may be stored satisfactorily for up to 10 days only if they are enclosed in plastic. Unenclosed pods rapidly lose weight and shrivel. The optimum temperature for the storage of pods enclosed in plastic was 7°C, which permitted storage for a period of 10 days followed by 3 days shelf life at room temperature (22°C). Although weight loss was high, particularly during the shelf life period, the visual quality of the pods remained unaffected even when the weight reduction was 15-20%. The pods of Clemson Spineless stored well at 10°C for 10 days, followed by 3 days shelf life and weight loss was less compared to Boyiatiou. The small pods of Boyiatiou proved less prone to discoloration and the occurrence of spots and decay than Clemson Spineless, specifically when enclosed in plastic. Despite high weight loss the unenclosed pods of Clemson Spineless exhibited a better optical appearance than those that were enclosed in plastic. Hence, while packaging is essential for storage of the small pods of Boyiatiou the larger pods of Clemson Spineless may be stored satisfactorily without packing. Among the different packing materials used for Boyiatiou, the best seemed to be the plastic box due to the lower humidity within the package in comparison with the films. Although okra pods are known to exhibit a high rate of respiration during storage, the rate of respiration of the small pods of cv. Boyiatiou was similar to that of the larger pods of cv. Clemson Spineless at the same storage temperature. Ethylene release during storage was similar in both cultivars at the same temperature, but was higher in Clemson Spineless during the subsequent shelf life period. During storage pods of Boyiatiou showed a progressive loss of starch and sucrose (as well as glucose at 15 days storage), whereas the concentrations of fructose and rafinose remained stable. Although an increase in fibre content was observed during storage, pod firmness decreased. From the experiment to determine the susceptibility of cv. Boyiatiou to low temperature (chilling) injury, it was found that chilling injury developed in pods stored at 2°C, and to a lesser extent in pods stored at 4 and 6°C over a 10 days period. The symptoms of chilling injury developed when pods were transferred to room temperature (22°C) for 3 days shelf life. Pods that were enclosed in plastic during storage showed fewer chilling injury symptoms than unenclosed pods. For the production of small pods of cv. Boyiatiou, as demanded within the Greek market, the nitrogen concentration used for fertilization during crop cultivation should not exceed 300 ppm. Though the N-level did not significantly affect the storage behaviour of the pods, increasing N rates caused an increase in NO₃ concentration within the pods and also affected pod colour and firmness. In conclusion, the present study defines the optimal storage conditions for small pods characteristic of the Greek cv. Boyiatiou, the susceptibility of these pods to chilling injury and nitrogen application during crop cultivation. The major compositional components of the pods (starch, sugars, fibre), the optical quality parameters (colour and optical assessment) plus firmness, and some physiological parameters (respiration and ethylene release) during storage are described. The storage requirements of Boyiatiou are compared with those of the large-fruiting cv. Clemson Spineless, the postharvest behaviour of which is generally referred to in the literature as characteristic of okra.