Ph.D

The present study entitled “Bionanocomposite edible coating for extending shelf life of banana and papaya” was carried out at the Department of Postharvest Management, College of Agriculture, Vellayani during the period of 2022-2024, with the objective of synthesis, characterization, and evaluation of bionanocomposite edible coating for shelf life and quality in banana and papaya. Chitosan nanoparticles (ChNPs) and Moringa leaf extract (MLE) loaded ChNPs were synthesized using the ionic gelation method with sodium tripolyphosphate as a crosslinking agent and Tween 80 as a surfactant. The size of the synthesized nanoparticles varied with the composition; ChNPs 0.5 % recorded a particle size of 77.47 nm, 0.3 % moringa leaf extract loaded chitosan nanoparticles were of 82.03 nm, 0.6 % moringa leaf extract loaded chitosan nanoparticles with 93.90 nm and 0.9 % moringa leaf extract loaded chitosan nanoparticles recorded a size of 95.36 nm as assessed by Scanning Electron Microscopy. The polydispersity index of the bionanocomposites ranged from 0.380 to 0.404 and the zeta potential varied between 27.40 to 46.60 mV. Fourier Transform Infrared Spectroscopy (FTIR) confirmed that moringa leaf extract was successfully loaded to chitosan nanoparticles. The antifungal in vitro and in vivo activity of bionanocomposites against Colletotrichum musae and Colletotrichum gloeosporioides that cause anthracnose in banana and papaya respectively was analyzed. In vitro evaluation of bionanocomposites by agar well diffusion assay against Colletotrichum musae was done at 750 ppm and 1000 ppm concentrations. Among the bionanocomposites, Ch 0.5% + 0.9 % MLE NPs showed the highest zone of inhibition after 4 days (1.03 cm) and 6 days (0.93 cm) of incubation at 1000 ppm concentration. In vitro evaluation of bionanocomposites against Colletotrichum gloeosporioides at 1000 ppm and 1250 ppm concentration was assessed and the bionanocomposites Ch 0.5% + 0.9 % MLE NPs recorded the highest zone of inhibition at 1250 ppm after 7 days (0.93 cm) and after 9 days (0.48 cm) of incubation. The moringa leaf extract of 0.3 %, 0.6 % concentration and 1 % acetic acid did not show inhibition against C. musae and C. gloeosporioides. The optimally ripened banana and papaya fruits were selected for conducting in vivo study. The fruits were sanitized by ozonization (2 ppm), and sprayed with bionanocomposite coatings. The treated fruits were inoculated with C. musae and C. gloeosporioides respectively and were kept for incubation. In vivo evaluation of bionanocomposites against C. musae in banana revealed that, the bionanocomposite of Ch 0.5% + 0.9 % MLE NPs at 1000 ppm recorded the lowest PLW (6.25 %), disease incidence (50.00 %) and disease index (36.33 %) after 9 days of incubation. It also delayed the days for symptom development (7.75 days) and showed the highest shelf life (8.50 days) compared to the pathogen-inoculated control (4.50 days). In C. gloeosporioides inoculated papaya fruits, Ch 0.5% + 0.9 % MLE NPs at 1250 ppm showed significant reduction in PLW (6.39 %), disease incidence (52.78 %) and disease index (35.63 %) after 8 days of incubation. Additionally, the treated papaya delayed the days taken for symptom development in papaya fruits (5.75 days) and recorded the highest shelf life (7.50 days) compared to the pathogen-inoculated control (4.00 days). Good quality banana fruits (cv. Nendran) of uniform size and maturity were de handed and sanitized with ozonization at 2 ppm. The sanitized fruits were subjected postharvest spraying of different bionanocomposite edible coating treatments viz., ChNPs 0.5%, Ch 0.5 % + 0.9 % MLE NPs (1000 ppm), MLE 0.9%, Chitosan 0.5%, and without any treatment (control). The treated fruits were packed in corrugated fibre board boxes, and stored at room temperature (27±1 °C) and refrigerated condition (15±1 °C). After 12 days of storage under room temperature, the fruits treated with Ch 0.5 % + 0.9 % MLE NPs recorded a pulp percentage of 66.72 % with a TSS of 22.70 °Brix, 0.44 % of acidity, 15.71 % of total sugars, 16.74 % of reducing sugars, 0.262 mg 100g-1 of carotenoids, 4.60 % of starch with minimum decay percentage (27.78 %), PLW (12.68 %) and maintained highest texture (10.42 N), total phenol (51.46 mg GAE 100g-1), total flavonoid (15.73 mg QUE 100g-1) and enhanced the shelf life to 11.67 days compared to control (6.67 days). Under refrigerated storage (15±1 °C) of bionanocomposite coated Nendran banana, fruits coated with Ch 0.5 % + 0.9 % MLE NPs showed a pulp percentage of 68.10 %, 20.90 °Brix of TSS, 0.36 % of acidity, 16.22 % of total sugars, 16.14 % of reducing sugars, 0.247 mg 100g-1 of carotenoid, 6.19 % of starch with minimum decay percentage (21.90 %), PLW (10.95 %) and maintained highest texture (19.62 N), total phenol (59.87 mg GAE 100g-1), total flavonoid (16.17 mg QUE 100g-1) after 35 days of storage, with enhanced shelf life of 34.67 days compared to fruits without any treatment (control) recorded a shelf life of 22.33 days. Papaya fruits (cv. Red lady) of uniform size, shape, maturity, at colour break stage were collected and sanitized (ozonization 2 ppm) followed by postharvest spraying with different bionanocomposite edible coating viz., ChNPs 0.5%, Ch 0.5 % + 0.9 % MLE NPs (1250 ppm), MLE 0.9%, chitosan 0.5% and control. The treated fruits were packed in corrugated fibre board boxes, and stored at room temperature (27±1 °C) and refrigerated condition (15±1 °C). Based on physical, physiological, biochemical, and sensory parameters, the fruits stored under room temperature with Ch 0.5 % + 0.9 % MLE NPs coating recorded the 12.93 °Brix of TSS, 0.24 % of acidity, 11.11 % of total sugars, 7.16 % of reducing sugars, 1.19 mg 100g-1 of carotenoids with minimum decay percentage (43.25 %), PLW (13.33 %) and maintained highest texture (16.06 N), total phenol (42.26 mg GAE 100g-1), total flavonoid (10.17 mg QUE 100g-1) after 13 days of storage, with enhanced shelf life of 12.50 days as compared to control (4.83 days). Under refrigerated condition (15±1 °C) after 35 days of storage, the treatment Ch 0.5 % + 0.9 % MLE NPs showed the 12.32 °Brix of TSS, 0.21 % of acidity, 10.75 % of total sugars, 6.41 % of reducing sugars, 1.17 mg 100g-1 of carotenoids with minimum decay percentage (17.78 %), PLW (12.16 %), and maintained the highest texture (15.23 N), total phenol (43.13 mg GAE 100g-1), total flavonoid (12.34 mg QUE 100g-1) with enhanced shelf life of 33.67 days compared to control (19.33 days). Chitosan nanoparticles and moringa leaf extract-loaded chitosan nanoparticles were synthesized by using the ionic gelation method with particle size below 100 nm as recorded by Scanning Electron Microscopy. In vitro evaluation of bionanocomposites revealed that Ch 0.5 % + MLE 0.9 % NPs exhibited the highest zone of inhibition against C. musae at 1000 ppm and C. gloeosporioides at 1250 ppm concentration. In vivo evaluation of bionanocomposites observed that Ch 0.5 % + MLE 0.9 % NPs was the most effective in controlling the C. musae at 1000 ppm concentration in banana and C. gloeosporioides at 1250 ppm concentration in papaya. Banana fruits (cv. Nendran) coated with bionanocomposites of Ch 0.5 % + MLE 0.9 % NPs (1000 ppm) maintained physical, physiological, biochemical, and sensory parameters throughout the storage under room temperature (27±1 °C) and refrigerated condition (15±1 °C) with an enhanced shelf life up to 11.67 days at room temperature and 34.67 days at refrigerated storage. Papaya (cv. Red lady) treated with Ch 0.5 % + MLE 0.9 % NPs (1250 ppm) maintained better physical, physiological, biochemical, and sensory parameters throughout the storage and recorded an extended shelf life of 12.50 days room temperature storage and 33.67 days under refrigerated storage.