Desenvolvimento de embalagens ativas absorvedoras de etileno utilizando nanofibras e fibras ultrafinas incorporadas de TiO2

Abstract

An emerging technology that aims to extend the shelf life of fruits and vegetables is the use of compounds with photocatalytic action against ethylene, promoting its complete conversion into carbon dioxide and water, as is the case of titanium dioxide (TiO2). As a result, the thesis is divided into two studies. Study 1 is addressed in Chapter 1, entitled “Photocatalytic action of zein-TiO2 nanofibers as ethylene absorbers in the storage of cherry tomatoes". electrospinning, and to evaluate its photocatalytic activity against ethylene during storage of cherry tomatoes.First, in experiment I, zein nanofibers were produced (30% zein (w/v) dissolved in 70% ethanol (v/v)), incorporated TiO2 at concentrations of 0, 1, 2, 3, 4 and 5% (w/w). The polymer solutions were evaluated for apparent viscosity and electrical conductivity. The nanofibers were characterized for morphology, size distribution, properties thermogravimetric measurements, functional groups, and contact angle. In experiment II, the nanofibers that presented the smallest average diameter (incorporated nanofibers of 5% TiO2, with 63 nm), were selected for the application tests in the form of a sachet and used in conservation of cherry tomatoes. The ethylene concentration inside the packages was periodically monitored by gas chromatography. The addition of TiO2 reduced the diameter of the nanofibers and altered their thermal properties. In the evaluation of functional groups, an interaction between zein and TiO2 was observed. In the application test, the packages containing the sachet of zein nanofiber membranes incorporated in TiO2 exhibited a lower concentration of ethylene, demonstrating the potential of the sachets as ethylene absorbers, for application as active packaging in the conservation of tomatoes. Study 2, discussed in Chapter 2, is entitled “Production and characterization of ultrafine fibers of germinated and non-germinated wheat starch incorporated with TiO2”. In this study, the objective was to produce and characterize ultrafine starch fibers incorporated with TiO2. For this purpose, ultrafine fibers of germinated and non-germinated wheat starch were produced, both at concentrations of 20 and 30% (w/v), incorporated with TiO2 at concentrations of 0, 3, and 5% (w/w). Polymeric solutions were evaluated for electrical conductivity and rheology. The ultrafine fibers were characterized according to morphology, size distribution, thermogravimetric analysis and functional groups. The electrical conductivity of polymeric solutions increased with the increase in TiO2 concentration. As for rheology, the polymeric solutions showed non-Newtonian pseudoplastic behavior. The ultrafine fibers presented homogeneous and cylindrical morphology, the addition of TiO2 reduced the diameter of the ultrafine fibers in relation to the samples without incorporation of this compound, and altered their thermal properties. Interactions between different starches and TiO2 were observed based on the infrared spectrum by evaluating the functional groups. From the data of these studies, it is expected to obtain an application of nanofibers and ultrafine fibers in the process of conservation of climacteric fruits, by ethylene photocatalysis, and thus, to extend their shelf life.