DEVELOPMENT OF EDIBLE COATING WITH ZNO NANOPARTICLES FOR INCREASING GUAVA POSTHARVEST SHELF LIFE

Fruits such as guava are perishable foods that result in high post-harvest losses, leading to an increasing search for alternatives to reduce fruit deterioration during the post-harvest period. Coatings are one of the most recent alternatives to help preserve food. So, this work aimed to develop nanocomposite coatings using chitosan (C), rosin resin (R), incorporated with zinc oxide (ZnO) nanoparticles for application in post-harvest conservation of guavas. The effect of coatings on physicochemical properties of fruits stored at room temperature was investigated. The coatings were applied to fruits randomly divided into four treatments, as following: NC (no coating), CR (1.2% chitosan +0.6% resin) and CRZn (1.2% chitosan + 0.6% resin +0.05% ZnO). The fruits were immersed in the coating solution. After a brush was used to remove the excess solution and then stored for 14 days at 22.47 ±1.34 °C and 82.02 ±8.73 %RH. The coatings with CR or CRZn improved the postharvest shelf life and stability of the guavas, minimizing weight loss, as well as changes in colour and texture, titratable acidity, pH, soluble solids compared to uncoated guavas. The coatings increased the shelf life of the guavas by four more days. No significant differences were observed between coatings with and without ZnO nanoparticles. After twelve days of storage, guavas coated with CR and CRZn showed the lowest weight loss (13.41% and 12.61%, respectively) when compared to the control (16.66%). The coated guavas had the highest values of luminosity (L*) (CR: 66.77±4.21 and CRZn: 68.41±3.19) and the lowest values of a* (CR: 18.23±6. 44 and CRZn: 17.58±3.40), which correspond to the red colour, indicating maintenance of quality and delay in ripening during storage. Overall, the results obtained in this study showed a potential for using biodegradable chitosan-based coatings added with rosin resin and ZnO nanoparticles for coating guavas.