Moringa leaf extracts coating on postharvest of Avocado fruit quality and its biofungicidal effect
Moringa leaf extracts coating on postharvest of Avocado fruit quality and its biofungicidal effect
Investigated the efficacy of edible gum arabic (GA) and carboxymethyl cellulose (CMC) containing moringa (M) leaf extract as postharvest treatments for maintaining organoleptic quality and controlling Colletotrichum gloeosporioides on ‘Maluma’ avocado fruit. For the quality study, after the fruit was dipped into the treatments: GA 10% + M, GA 15% + M, and CMC 1% + M and uncoated fruit served as control, the fruit were then stored at 5.5 8 °C [95% relative humidity (RH)] for 21 days, and moved to ambient conditions at 21 ± 18 °C (60% RH) for 7 days to simulate retail condition. Fruit quality study results showed fruit coated with GA 15% + M and CMC 1% + M had lower mass loss (3.66%) and retained firmness (62.37 N) compared with other treatments. In this biofungicidal study on antimicrobial properties of extracts, treatments against fungi strains using an in vitro test were investigated, which showed treatments of moringa leaf extract, GA 10% + M, and GA 15% + M suppressed radial mycelial growth of C. gloeosporioides by 30%, 28%, and 33%, respectively.GA 15% + M and CMC 1% + M retained fruit firmness and lowered weight loss and suppressed mycelial growth of C. gloeosporioides on ‘Maluma’ avocado fruit. These edible coatings could therefore be an alternative organic postharvest coating treatment and could potentially be commercialized as a new organic biofungicide for the avocado fruit industry.
A total of 180 avocado fruit (Maluma cultivar) used in this study ‘Maluma’ avocado fruit were being washed with distilled water. They were then assigned to postharvest treatments: Control (untreated), GA 10% + moringa 10%, GA 15% + moringa 10%, and CMC 1% + moringa 10%. Fruit were dipped in treatment solutions, and air-dried on a laboratory bench at room temperature (21 ± 1 °C) for 30 to 45 min. After drying, fruit were packed into commercial boxes and transferred to a cold room which had a delivery air temperature set at 5.5 °C and RH set at 90% ± 2% for 3 weeks, simulating shipping conditions. After 3 weeks of cold storage, fruit were transferred to ambient conditions (21 ± 1 °C, RH 60%) for 7 d, simulating ripening and retail conditions.
Moringa tissue extraction process ten grams of moringa plant tissue was extracted with 1 L of ethanol 70% (v/v) for 2 h with constant agitation at 4 °C. Extracts were concentrated in a rotary evaporator, and 20 mL distilled water was added. Finally, crude extract was subjected to sequential liquid-liquid extraction with hexane, chloroform, and finally ethyl acetate.
The firmness of ‘Maluma’ avocado fruit was significantly affected by the interaction between storage time and coatings. This could be explained by the sharp decline of firmness in control fruit in comparison with the steady decline in coated fruit. Loss of firmness gradually increased with storage time for both coated and control fruit. At the end of storage time, uncoated fruit clearly had the lowest firmness (22.20 N). On the other hand, GA 15% + M (62.37 N), CMC 1% + M (59.93 N), and GA 10% + M (59.48 N) maintained higher firmness throughout the study. A similar trend was also observed in mass loss, in which minimal change was observed in fruit coated with the previously mentioned coatings. It can be argued that the restriction of moisture loss was the major factor why coatings retained higher firmness than uncoated fruit.
In this study, it could be argued that coating fruit with GA 15% + M, CMC 1%+M, and GA 10%+M resulted in a modified atmosphere with reduced O2 and increased CO2 levels, causing a reduction of enzymatic activities in coated avocados compared with uncoated avocados.Fruit colour is the primary and most used perception parameter in determining the quality of fresh horticultural produce.The lightness (L*) gradually decreased during storage in both coated and uncoated fruit. The fruit coated with 15%, 10% GA +M, and CMC 1% + M retained their lightness values at the end of the experiment.Thus, the performance of the coating may be improved because of its good adherence and compatibility with fruit peel of high lipid content, as bilayer, enhances the fruit appearance and attractiveness.The ability of these coatings to retain avocado green colour suggest that coatings were able to delay fruit ripening.
The colour change in uncoated fruit was enhanced and they attained purple to black colour during shelf life compared with the coated fruit. Although the fruit coated with GA 15% + M, GA 10% + M, and CMC 1% + M remained green even after 28 d of storage, it is possible that GA and CMC provided a thick barrier against ethylene production and gas exchange between inner and outer environments, and therefore delayed the ripening of the fruit during storage. In this study, coating of avocados with GA and CMC delayed colour change, which was probably due to an increase in CO2 and decrease in O2 levels. This makes sensory evaluation an important factor in the development of edible coatings. The fruit coated with GA 10% +M, GA 15% +M, or CMC 1% +M had the highest scores in all parameters after 28 d of storage, whereas those coated with control and GA 15% developed poor taste, mouthfeel, and odor and had lower scores of overall acceptability. GA 15% + M were the least effective treatment in sensory fruit quality, as the treatment attained lower scores during sensory evaluation.Overall, the results suggest that GA 10% + M, GA 15% + M, and CMC 1% +M can be used successfully as an edible coating for prolonging the shelf life and improving avocado fruit quality. A maximum inhibition (33%) in mycelial growth was observed in GA 15% + M. This result evident that the incorporation of moringa leaf extract with edible coatings improved the antimicrobial activity.
In conclusion, the results showed that GA 15%+M, followed by GA10%+M and CMC 1% + M, were the most effective treatments in reducing mass loss and firmness loss, delaying colour changes as well as in inhibiting the growth of C. gleosporioides (33%). Overall, the study demonstrated that edible coatings incorporated with moringa leaf extract reduced mass loss, retained firmness, and delayed colour changes, as well as antifungal properties against C. gleosporioides compared with the control in ‘Maluma’ avocado. These edible coatings could therefore be an alternative organic postharvest treatment to be used by avocado industries in future.
Kubheka, S.F., Tesfay, S.Z., Mditshwa, A. and Magwaza, L.S., 2020. Evaluating the efficacy of edible coatings incorporated with moringa leaf extract on postharvest of ‘Maluma’avocado fruit quality and its biofungicidal effect. HortScience, 55(4), pp.410-415.
