الملخص الإنجليزي
Bananas are one of the delicate fruit that suffer from mechanical damage and quality degradation during improper preharvest and postharvest practices. This study aimed to determine the effect of these practices on the quality changes of banana fruit in Oman. The study applied different experiments starting with a survey that assessed local banana fruit production at Farmgate based on key agricultural practices. Another experiment was carried out to evaluate the most common physicochemical quality attributes of the common banana fruit ‘Fard’ in Oman. A total of 4 different experiments were conducted to investigate the effect of mechanical damage using simulated handling practices and storage on banana quality. The effect of transport and packaging was also examined to determine the potential effects of these two practices on banana quality. The machine vision system was implemented in the majority of the studies to help identify the bruise damage intensity and quality attribute changes.
The results from the survey indicated that the banana fruit required a huge care by the farmers from the farm to the market. To provide bananas with high quality and quantity, the majority of farmers preferred to use flooding irrigation. Banana farmers used some specific practices to protect bananas from damage and to maintain the quality for longer periods during storage by using sponges, thick sheets, and proper packages. After harvest, the banana is subjected to different physiological changes when stored at ambient temperatures as indicated in the first laboratory experiment which lasted for a 20 days storage period. Storing banana ‘Fard’ at ambient conditions reduced the weight, transpiration rate, and firmness of the fruit. The study revealed a continuous change in skin color which was strongly correlated with the chemical attributes of bananas like total soluble solids, titratable acidity, sugar: acid ratio, and pH.
For the four simulated handling experiments, two techniques were used, including a pendulum impactor and a drop impact test. The first experiment investigated the effect of mechanical damage of different impact energies generated by a pendulum impactor and evaluated the bruise intensity and quality changes of bananas after 12 days of storage at different storage conditions. The findings of the study revealed that the bruise susceptibility and electrolyte leakage in the banana fruit significantly increased as impact damage increased. Regarding color measurements, the results of image processing emphasized that storage at 13°C exhibited the ideal color change in bruised fruit, which revealed a slow increment in lightness and yellowness until the last day of storage. Bananas conditioned at 22°C after being impacted by high damage recorded the highest total soluble solids and lower acidity.
The second experiment used the drop impact test to assess the fractal dimension, browning incidence, and grayscale values using machine vision to describe the bruise magnitude and quality of mechanically damaged ‘Fard’ bananas bruised from 20, 40, and 60 cm drop heights by 66, 98, and 110 g ball weights conditioned at different storage temperatures (5, 13, 22°C) after 48 hours. The results demonstrated that bananas bruised from the highest force and stored at 5 and 22°C reported the lowest fractal dimension and grayscale values and highest browning incidence and bruise susceptibility values after 48 hours of storage.
The third study related to simulated handling by drop impact test performed the machine vision system and image process analysis to measure the bruise parameters of the damage zone and external quality attributes of 18 treatments generated from bruised (30 cm and 60 cm drop heights) and non-bruised (control) ‘Fard’ and ‘Somali’ banana cultivars stored at 5, 13, and 22°C for 21 days. The results recorded that increasing impact damage from 30 cm to 60 cm in both banana cultivars could significantly influence susceptibility to bruising. Digital image analysis was effectively used to determine the surface area of both cultivars. It was also found that the fractal dimension of the bruised zone increased as impact damage and storage duration increased, particularly in high-impact (60 cm) ‘Fard’ banana fruit at 5 and 22°C, respectively.
The last experiment used a simulated impact drop test was carried out to determine the effect of repeated impact drops in different tested zones (top, middle, and bottom) of banana fruit at 13 and 22°C for 15 days. The study used the response surface methodology to evaluate the interaction and effects of the factors (storage days, storage temperature, repeated impact, banana zone) on several quality attributes. The results indicated that the majority of studied parameters like bruise area, weight loss, surface area reduction, vitamin content, and redness-greenness values were significantly affected by storage days, storage temperatures, and repeated impact. The results of the surface plot revealed that the storage temperature, storage days, and repeated damage should be reduced, controlled, and monitored to minimize bruise area, weight loss, and surface area loss, maximize vitamin content, and optimize the changes of color values.
The last experiment of the thesis which examined the effect of the package on the quality of banana fruit during transportation reported that the CB1 (one piece-single wall-3 ply) package design exhibited better protective performance than the CB2 (two piece-double wall-5 ply) package for banana transportation as CB1 showed less package transmissibility compared to CB2. The package as an independent variable showed the highest effect on the weight loss, lightness, and yellowness of the banana. The vibration increased the occurrence of surface area reduction, weight loss, and conversion of color from green to yellow during 10 days storage.
Generally, the fractal image analysis conducted in this work was highly effective in describing the bruising magnitude of bananas under different conditions. Careful handling to prevent mechanical damage and storage at lower or recommended storage temperature (13°C) for bananas can enhance the quality for a long period. Also, using the appropriate package design and structure is very important to avoid damage and quality degradation in fruit quality during transportation and distribution.
