Active polyvinyl alcohol films with enhanced strength, antioxidant and antibacterial properties by incorporating nanocellulose and tannin.

There is an increasing demand of food packaging materials from sustainable bio- polymers. In this study, tannin-cellulose nanocrystal (TCNCs) fillers were first prepared using dialdehyde cellulose nanocrystal (DACNCs) and tannin through the nucleophilic addition reaction, and then added to PVA matrix as reinforcement fillers to fabricate active food packaging films. FT-IR analysis confirmed the successful reaction between PVA and TCNCs. The incorporation of TCNCs imparted high antibacterial, UV blocking and antioxidant capabilities to the composite films, maximumly achieving a 75 % DPPH free radical scavenging rate while blocking all UV rays. The addition of TCNCs resulted in an increase in water contact angle, alongside decreases in swelling ratio and solubility, indicating the enhanced water resistance. The composite films exhibited a 66.7 % decrease in oxygen permeability (OP) compared to the PVA film, with a slight increase observed in water vapor permeability (WVP). The tensile strength increased from 49.65 MPa to 74.17 MPa by adding 15 % of TCNCs due to the chemical crosslinking between PVA and TCNCs. Wrapping cherry tomatoes with these films prolonged the postharvest life compared to using polyethylene (PE) and pure PVA films. Films derived from sustainable biopolymers show great potential for use in fresh produce packaging.

Qin J ，Huang X ，Xu Q ，Jin L ... -  《-》

Novel food preservation strategy using sprayed PVA/chitosan-based coatings activated by macroemulsions of chamomile essential oil adsorbed on activated carbon.

Active films based on polyvinyl alcohol (PVA) and chitosan (CS) were developed by encapsulating chamomile essential oil using an emulsification process, followed by adsorption onto activated carbon (AC) to stabilize the oil droplets. Microscopic analysis showed that the average size of the micelles was between 0.1 μm and 1.5 μm. The micelles obtained were incorporated into PVA/CS film formulations with different concentrations of chamomile essential oil (5 %, 10 %, 15 % w/w), and the optical, physical, mechanical, antibacterial, and antioxidant properties as well as the release rate of the encapsulated oil were studied to test their application in food packaging. The SEM images showed a homogeneous dispersion of the EO in the polymer matrix containing AC, due to the formation of hydrogen bonds, which is confirmed by the FTIR results and is accompanied by an increase in the viscosity of the film-forming solutions, a decrease in the crystallinity and an improvement in mechanical properties by an increase in elongation at break (15.95 ± 0.10 to 47.02 ± 0.06 %) of the films produced. In addition, some properties of the PVA/CS films were increased by the addition of EO-AC, notably thickness (0.097 ± 0.12 to 0.144 ± 0.01 mm) and opacity (1.632 ± 0.11 to 8.266 ± 0.12), while the water absorption rate and solubility of the films decreased. PVA/CS-EO-AC films exhibit good antioxidant and antibacterial activity against E. coli and S. aureus, high barrier properties (UV-blocking) and a controlled release of bioactive molecules contained in EO. The PVA/CS/EO-AC coating reduced the weight loss of the tested apples to (3.31 ± 0.29 %) compared to apples packaged in polyethylene film, and maintained their appearance after 3 weeks of storage. These results offer the possibility of reducing food waste through this new coating strategy based on the encapsulation of EO.

Bouftou A ，Aghmih K ，Belfadil D ，Rezzouq A ，Lakhdar F ，Lamine M ，Gmouh S ，Majid S ... -  《-》

Physicochemical and biological evaluation of 'click' synthesized vinyl epoxide-chitosan film for active food packaging.

Chitosan (Cs) being a natural biopolymer serves as an excellent template to construct active packaging materials for achieving sustainable development. In this study, Cs was chemically modified via epoxide ring opening click reaction using vinyl epoxide to obtain a novel chitosan vinyl epoxide (Cs-VE) derivative with hydroxyl and olefinic functional groups. The Cs-VE transparent film was fabricated through the eco-friendly solution casting technique. A meticulous investigation into the chemical structure and physicochemical properties of the synthesized films was conducted using FT-IR, 1H NMR and XRD analyses. The thermal stability and homogeneity of the film were verified by thermogram and FE-SEM images respectively. Improved mechanical properties (tensile strength of 24.64 MPa and 12.08 % elongation at break) and excellent UV-light blocking ability (9.3 % transmittance at 350 nm and 22.15 % transparency at 600 nm) were observed. Also, important parameters such as water vapor permeability (WVP), swelling degree, water solubility and UV-barrier properties were found to be adequate for food packaging application. Similarly, enhanced antioxidant activity with 27.2 % and 73.6 % radical scavenging against DPPH and ABTS radicals respectively was observed for the synthesized Cs-VE film. The film showed antimicrobial activity against both bacteria and fungi. These results along with food packaging studies on Grewia asiatica fruit established the developed Cs-VE film as a suitable candidate for active food packaging application.

D PM ，Chawla R ，Dutta PK 《-》

Improving the antibacterial properties of polyethylene food packaging films with Ajwain essential oil adsorbed on chitosan particles.

The aim of this research is to develop a composite antibacterial film for food packaging using low-density polyethylene (LDPE), linear low-density polyethylene (LLDPE), polyethylene-graft-maleic anhydride (PE-g-MA), and incorporating chitosan (CS) particles onto which ajwan essential oil (AEO) is adsorbed. The films were characterized using various techniques, including Fourier-transform infrared spectroscopy (FTIR), Gas chromatography/mass spectroscopy (GC-MS), X-ray diffraction (XRD), tensile testing, oxygen transmission rate (OTR), thermogravimetric analysis (TGA), scanning electron microscopy (SEM), and antibacterial assays. FTIR results confirmed the presence of CS and/or AEO in the films. Mechanical testing indicated a decrease in tensile strength and an increase in elongation at break with the addition of AEO, while CS reduced elongation. In the sample containing only 7.5% chitosan (PE-7.5-0), the oxygen permeability was reduced to 910 cm2/m2·day·bar due to the presence of CS. However, the inclusion of AEO in the sample (PE-0-10) increased the oxygen permeability to 2200 cm2/m2·day·bar, which is higher than that of the control sample (PE-0-0) with an oxygen permeability of 1680 cm2/m2·day·bar. The antibacterial activity results demonstrated a synergistic inhibitory effect of CS and AEO. Data from GC-MS and inhibition zone (IZ) tests indicated that while chitosan alone does not exhibit significant antibacterial activity due to its incorporation in the bulk of the film, its combination with AEO enhances antibacterial efficacy. This enhancement occurs as the oil is adsorbed and protected from evaporation during the film formation process. Overall, the findings from this research suggest that the composite film PE-7.5-10, which possesses suitable mechanical properties and significant antibacterial activity, could be an effective candidate for food packaging applications.

Shiva K ，Soleimani A ，Morshedian J ，Farahmandghavi F ，Shokrolahi F ... -  《Scientific Reports》

Development of polyvinyl alcohol/carboxymethylcellulose-based bio-packaging film with citric acid crosslinking and clove essential oil encapsulated chitosan nanoparticle pickering emulsion.

This study developed polyvinyl alcohol (PVA)/carboxymethylcellulose (CMC)-based films, using citric acid (CA) as a non-toxic crosslinking agent, to enhance the shelf life of water-soluble packaging films. Clove essential oil (CEO)-loaded chitosan nanoparticles (CSNPs) were prepared via Pickering emulsion and incorporated into PVA/CMC/CA composite films. The encapsulation of CEO was confirmed by FTIR and optical microscopy. Thermal properties were analyzed using thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC), revealing improved thermal stability and a decrease in glass transition temperature (Tg) upon crosslinking. The formation of ester bonds was confirmed by ATR-FTIR and 13CNMR. Water contact angle (WCA) measurements showed a decrease in hydrophilicity, enhancing the barrier properties of the films. SEM images demonstrated good dispersion of CSNP/CEO within the matrix, improving mechanical and barrier properties. The films exhibited a 30 % reduction in water vapor permeability and water solubility. Controlled release studies indicated that the composite films sustained CEO release, extending the shelf life of cherry tomatoes. Thus, these PVA/CMC/CA-CSNP/CEO composite films offer strong potential for food preservation applications.

Thungphotrakul N ，Prapainainar P 《-》