Efficacy Of Waxing Innovations To Extend Shelf Life And Preserve Postharvest Quality Of Mango Fruits

Abstract

Mango (Mangifera Indica L.) is one of the major fruits produced in Kenya mostly for the domestic market, and to a small extend for export markets. Mango is widely adapted to different Agro-Ecological Zones and its production is mainly by smallholder farmers who depend on it for their livelihoods. However, there are many challenges which have inhibited realization of the full potential of mango in Kenya. High postharvest losses estimated to be 40 – 50% is one of the challenges facing mango value chain actors. The high losses result from various factors including poor harvesting practices, pest and diseases, lack of postharvest technologies, among others. Various postharvest technologies such as controlled atmosphere storage, refrigeration, modified atmospheric packaging, among others have been used with great success, but are out of reach for small holder farmers who are resource constrained. Waxing of fruits is an old practice which has been demonstrated to have benefits on various fresh commodities such as avocados, mangos, citrus, apples, loquats, among others. However, application of waxing technologies in mango fruit has not been tried commercially in Kenya. This study was conducted to evaluate the efficacy of two waxing options on prolonging the shelf life of two popular mango varieties in Kenya under different storage conditions. Fruits for the study were harvested from 6 – 10-year-old trees on commercial farms in Machakos County. In the first experiment, ‘ngowe’ and ‘apple’ mango fruits were harvested at mature green stage and transported in padded crates to the postharvest laboratory where they were sorted for uniformity, washed with disinfected water, brushed gently with Decco Clear (food brush sanitizer), dipped in hot water (45-55C) and placed on wire shelves for air drying. Each variety was then batched into five groups for different treatments. The treatments included Shellac wax (3% and 5%, w/w), Mango wax, Mango wax+prochloraz (fungicide) and x untreated (control). The fruits were then packed in open carton boxes and stored in different storage conditions including ambient (25C) and simulated commercial cold storage (12C). A random sample of three fruits was taken from the different treatments and storage environment for analysis of attributes associated with ripening. The ripening attributes measured included physiological (respiration and weight loss) and physical (peel/flesh firmness and peel/pulp color). In the second experiment, the best performing treatment(s) from each storage option in experiment 1 was selected and applied on the mango fruits (‘ngowe’ and ‘apple’) to establish their effect on postharvest quality attributes. The parameters measured included total titratable acidity (TTA), total soluble solids (TSS), total sugars, beta carotene and vitamin C. Completely Randomized Design with factorial arrangement was used as the study design. Results from the study showed waxing to have a significant (p<0.05) effect on shelf life of mango fruits. Waxed fruits had an extended shelf life of 3 and 4 days at ambient storage conditions for ‘ngowe’ and ‘apple’ mango fruits respectively and for 6 days under cold storage (12C) for both varieties. Waxing suppressed the rate of respiration for both mango varieties in the different storage conditions compared to the control. Under ambient storage conditions, untreated ‘apple’ mango fruits had a high respiratory peak of 85.09ml/kg hr (day 10) compared to a low average peak of 51.55ml/kg hr (day 14) for the treated fruits. Weight loss was significantly reduced by waxing. Control ‘apple’ mango fruits under ambient storage conditions lost 12.4% of the initial weight compared to an average of 7.75% weight loss for the treated fruits by end of the storage period. Similarly, in the case of cold-stored fruits, untreated ‘apple’ mango lost 5.5% compared to an average of 3.7% for the treated fruits by end of storage period. Other ripening related physiological and physical changes followed a trend that correlated positively with water loss and respiratory activity. Wax treated fruits maintained relatively higher hue angles (peel and pulp) and higher firmness (peel and pulp) throughout the storage period compared to control fruits. In the second experiment, results showed waxing to be effective in delaying the rate of loss of the fruit’s quality attributes for both ‘ngowe’ and ‘apple’ mango fruits. Brix levels for the treated fruits remained relatively low especially for the fruits in the cold storage. Control ‘apple’ mango fruits had a high brix level of 20.88 ºbrix by day 15 compared to a lower average level of 19.05ºbrix for the treated fruits, by end of storage period (day 28). The other parameters (total titratable acidity, vitamin C, beta carotene and sugars) for the waxed fruits were also retained longer, showing a positive correlation with water loss and respiration. The results from this study show that waxing is an effective postharvest technology which can be used as an alternative technology to extend shelf life and maintain postharvest quality of mango fruits during storage, transportation or marketing. Key words: Cold storage, Ambient, Mango wax, Shellac wax, Shelf life, Postharvest quality.