Mode of action of chitosan coating on anthracnose disease control in papaya

The effect of a chitosan coating on antifungal activity and rate of respiration, chitinase and β,1-3 glucanase activities with reference to papaya variety 'Rathna' was investigated. One percent chitosan, extracted from locally available prawn waste, was selected as the effective concentration to inhibit spore germination via a series of experiments on potato dextrose agar. Rate of respiration and the concentration of CO in the internal cavity of chitosan-treated and untreated papaya were tested via gas chromatography. Chitinase and β,1-3 glucanase activities were tested in peel samples using gel diffusion and spectrophotometric assays, respectively. Complete inhibition of spore germination was observed in-vitro at treatments of 1% chitosan and above. This concentration significantly (P < 0.05) reduced both disease incidence and severity on inoculated fresh papaya. Significant (P < 0.05) decrease was observed in rate of respiration while internal CO concentration of the fruit increased (P < 0.05) with the chitosan treatment. Chitinase and β,1-3 glucanase activities of papaya variety Rathna subjected to chitosan treatment were much higher than in the untreated control. Chitosan shows antifungal activity to the anthracnose disease causing fungus and stimulates the defense response on the papaya peel by increasing the chitinase and β,1-3 glucanase activities. The antifungal activity of chitosan could be attributed to the induction of elicitation activity due to these defense enzymes. It also forms a semi-permeable coating around the fruit and extends storage life of papaya by reducing the rate of respiration and delaying ripening

Double Layer Coatings: A New Technique for Maintaining Physico-Chemical Characteristics and Antioxidant Properties of Dragon Fruit During Storage

A double layer coating was evaluated for maintenance of quality of dragon fruit during storage at 10 ± 2 °C and 80 ± 5 % RH for 28 days. Significant differences (p < 0.05) were observed between control and the treated fruit. However, a double layer coating with 600 nm droplet size + 1.0 % conventional chitosan showed promising results in all the tested parameters, while the fruit treated with 1,000 nm droplet size + 1.0 % conventional chitosan showed some negative effects on fruit surface. Increase in weight loss was 12.0 % in fruit treated with 600 nm droplet size and 1.0 % conventional chitosan as compared to the control. Antioxidants and gaseous analysis also proved the efficacy of double layer coatings with 600 nm droplet size + 1.0 % conventional chitosan. Thus it can be concluded from the present investigation that double layer coating could be used for maintaining quality in dragon fruit for up to 28 days without any off-flavours