Comparison Between Chitosan Nanoparticles and Cellulose Nanofibers as Reinforcement Fillers in Papaya Puree Films: Effects on Mechanical, Water Vapor Barrier, and Thermal Properties

Chitosan nanoparticles (Np) were prepared by ionic gelation method, with particle size of 58.54 ± 16.99 nm. Cellulose nanofibers (Nf) were extracted from soybean straws by a combined process of mechanical grinding and enzymatic hydrolysis, with diameters between 40 and 120 nm and variable length. The puree was prepared by using over‐ripe papayas and fillers (Np and Nf) incorporated separately at a concentration of 0.1% and 0.2% (% of filler to puree mass in dry bases) and subsequently cast into films. Mechanical characterization, both tensile strength and strain at break, were found to have significantly improved for those films reinforced with Nf. Values of tensile of 2.79 ± 1.20 MPa for chitosan and 7.30 ± 1.27 MPa for cellulose were measured for 0.2% additions. The presence of cellulose fibers (elongation of 9.33% ± 0.72%) had a greater effect on film plasticity than for chitosan Np (6.86% ± 2.17%) at 0.2% addition. About 0.2% of Nf also performed better than Np in reducing the water vapor permeation rate. Calorimetric analysis (TGA and DSC) indicated thermal stability of the composite films at temperatures above 100°C, with similar behavior between samples. POLYM. ENG. SCI., 59:E287–E292, 2019.