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Effects of edible coatings and moringa extracts on postharvest quality of papaya fruits.

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Carica papaya L., known as papaya is a member of the small family Caricaceae. It is an important fruit for both fresh and processed products. It is a good source of vitamin A, lycopene, polysaccharides and proteins. High consumption of papaya is known to contribute to the prevention of the chronic diseases such as cardiovascular disease. About 30-50% of the harvested papaya is reported to never reach the consumers due to postharvest spoilage. Postharvest spoilage can be attributed to the fact that it is perishable after harvesting. The level of spoilage depends on the management of pre-harvest (environment and cultural practices) and postharvest factors (handling, environmental conditions). The factors contribute largely to papaya quality deterioration by stimulating physiological/biochemical processes (respiration, transpiration) and microbial growth. Also, some of the factors affect papaya fruit quality at maturity stage, time of harvest and the harvest method. Various fungicides have been used to reduce postharvest spoilage. However, the negative effects on human health and the environment, accompanied with high costs, residues in plants has encouraged development of alternative approaches. The development of new natural preservatives and antimicrobials has increased as alternatives for fruit quality preservation. Edible coatings are amongst the natural methods of fruit quality preservation and protecting perishable food products from deterioration by retarding dehydration, suppressing respiration, improving textural quality, helping retain volatile flavour compounds and reducing microbial growth. The study evaluated the effect of edible coatings on papaya fruit quality, and antifungal activity of plant extracts against fungal pathogens that affect postharvest quality of fruits. In the first section of the study, Moringa oleifera extracts (leaf and seed) incorporated with chitosan and CMC (MLE+CH, MSE+CH, MLE+CMC and MSE+CMC) were used as an alternative for synthetic fungicides. The quality parameters were measured to observe the effect of treatments. The quality parameters that were assessed under cold and ambient storage conditions included pH, total titratable acidity, total soluble sugars, weight loss, firmness, peel colour, vitamin C, total flavonoids, total phenols, antioxidants and soluble sugars. Inhibitory effects of Moringa oleifera aqueous and ethanolic leaf and seed extracts (MLWE, MSWE, MLEE and MSEE) was evaluated in-vitro. Treatments applied (MLE+CH, MSE+CH, MLE+CMC and MSE+CMC) maintained papaya fruit quality compared to the control under both ambient and cold storage conditions. Treatment MSE+CMC showed better fruit quality maintenance compared to other treatments. MLWE, MSWE, MLEE and MSEE had relatively high inhibitory potential in all tested concentrations (10%, 20% and 30%) compared to the control treatment. A 100% mycelial growth inhibition in PDA agar amended with moringa extracted with ethanol was observed.


Masters Degree. University of KwaZulu-Natal, Pietermaritzburg.