Novas abordagens para otimizar a funcionalidade de recobrimentos à base de amido para manter a qualidade e conservação pós-colheita de frutos tropicais.

Abstract

This work was aimed at optimizing the functionality of starch-based coatings for maintaining quality and improving postharvest conservation of tropical fruits. The coatings studied were based on cassava flour (starch). Four experimental approaches were carried out: I – Propose a method to estimate the proportion of the surface with starch-based coatings, using digital processing of iodine-stained fruit images, and optimize the potential of the coating to adhere to the surface of different fruits; II – Develop a non-destructive method to estimate the diffusion of gases through a coated fruit surface, and study the impact of the coating-epidermis/gas exchange resistance on the composition of the coated papaya's internal atmosphere (atmi

); III – Monitor the internal O2 and CO2 concentrations in coated banana in relation to the proportion of the coated surface and the atmi

composition; IV – To evaluate the effects of combined coating with deep eutectic solvent (NADES) of ascorbic acid /choline chloride as a plasticizer on postharvest quality of mango. The main results were: I – Coatings ability to adhere on different fruit surfaces were improved by adding surfactant and increasing starch concentration in the dispersions. Adding Tween 40 in a cooled (18 oC) dispersion resulted in coating with high ability to adhere to the surface of different fruits (mandarin, pepper, banana and papaya), leading to a blockage of the pores, which may be due to the increased adsorption of the coating to the fruit’ surfaces without decreasing amylose-amylose interactions. II – The quantification of the resistance to the diffusion of gases through the fruit’ surface can be useful in defining the target atmi

in coated fruits, especially considering the interaction between the coating and the peel. In defining changes in the composition of the atmi

, the resistance to gas diffusion was the most appropriate variable than the respiratory rate. III – A 3.0%-starch coated the entire banana surface and resulted in anaerobiosis, indicated by a too low P i O2 and a burst in P i CO2 and increased respiratory quotient.

The P i O2 of 6 kPa in chambers attached on the fruit skin was the indicative of an adequate atmi was set for starch coated bananas, at which respiratory rate was minimized without development of anaerobiosis. Based on that, 1.5 and 2.0% starch coatings might be effective for delaying ripening, maintaining qualities, and extend shelf life of bananas. A proportion of 75% of coated surface was estimated as the limit for secure modified atmosphere for bananas. IV – The P i O2 immediately beneath the coated skin was much lower in mangoes coated with starch + NADES compared to those with starch + glycerol and those not coated. The atmi

ensured by starch + NADES coating was effective in delaying mango ripening and maintaining the superior quality in relation to the other coatings. In addition, mangos with starch + NADES prevented and / or reduced the damage induced by ROS, maintaining a higher content of ascorbic acid and balanced SOD, POD and APX activities compared to those with starch + glycerol and those not coated during storage.