Essential oils loaded-chitosan nanocapsules incorporation in biodegradable starch films: A strategy to improve fruits shelf life

Thermoplastic starch (TPS) films filled with chitosan nanocapsules (CN) containing essential oils (EO) were prepared aiming active packaging. Two different EOs were studied: Ho wood (H) and Cinnamon (C). Besides, different capsules concentrations were investigated (1, 3, and 5 wt%), and the films were evaluated by chemical structure, thermal stability, crystallinity, water vapor permeability, antimicrobial assays, and potential application for strawberry packaging. The TPS/CN-Ho wood films showed a strong interaction between chitosan-starch, mainly for 3 and 5 wt%, confirmed by XRD. The FT-Raman spectra of TPS/CN-Cinnamon film indicated that Cinnamon EO quickly migrated to starch films, probably due to the new crystal structure, named C-type, affecting the film's water permeability. The addition of 1 and 3 wt% CN loaded with Ho wood or Cinnamon EO to the films decreased the water permeability. 3 wt% CN was the optimum concentration to inhibit the Escherichia coli or Bacillus subtillis growth on the films, confirming their biological activity. The films' preservation properties were evaluated using strawberries, and films with 1 or 3 wt% loaded-CN could extend the strawberries' shelf life without fungi contamination. The developed TPS films can be used as active food packaging or other films for biomedical or pharmaceutical applications.

Biodegradable gelatin composite hydrogels filled with cellulose for chromium (VI) adsorption from contaminated water

Biopolymers are promising materials for water treatment applications due to their abundance, low cost, expandability, and chemical structure. In this work, gelatin hydrogels filled with cellulose in the form of pristine eucalyptus residues (PER) or treated eucalyptus residues (TER) were prepared for adsorption and chromium removal in contaminated water. PER is a lignocellulosic compound, with cellulose, hemicellulose, and lignin, while TER has cellulose as a major component. FT-Raman Spectroscopy and FTIR analysis confirmed the crosslink reaction with glutaraldehyde and indicated that fillers altered the gelatin molecular vibrations and formed new hydrogen bonds, impacting the hydrogels' crystalline structure. The hydrogen bond energy was altered by the cellulosic fillers' addition and resulted in higher thermal stability (~10 °C). Hydrogels presented a Fickian diffusion, where gelatin hydrogel showed the highest swelling ability (466%), and composites showed lower values with the filler content increase. The chromium adsorption capacity presented values between 12 and 13 mg/g, i.e., featuring an excellent removal capacity which is related with hydrogel crosslinked structure and fibers surface hydroxyl groups, highlighting gelatin hydrogel TER 5% with better removal capacity. The developed hydrogels were produced from biomacromolecules with low-cost and potential application in contaminated water.

Eco-friendly composites of polyurethane and sheath palm residues

This work prepared eco-friendly biocomposites of polyurethane (PU) and sheath palm residues, using castor oil as a polyol. PU composites filled with natural fibers were prepared at different loading rates: 0 to 20 wt.%. Results indicated that the sheath palm was hydrogen-bonded to PU chains and increased the foams' density. Pore size decreased with an increase in fiber content, from 256 to 116 µm. The fiber's addition improved the ductility of PU foams (compressive modulus from 4.74 to 0.26 MPa) and the foams' crystallinity index (from 5.4 to 15.4%). Compared to pristine PU, the composites showed high hydrophobicity (reaching 123° of contact angle for PU-15%) and thermal stability (Tonset from 96 to 96.3°), and high density (from 41 to 60 kg.m−3), making the developed composites an excellent option for environmental applications, such as oil removal and contaminant adsorption.