Formulation and application of poly lactic acid, gum, and cellulose-based ternary bioplastic for smart food packaging: A review

In future, global demand for low-cost-sustainable materials possessing good strength is going to increase tremendously, to replace synthetic plastic materials, thus motivating scientists towards green composites. The PLA has been the most promising sustainable bio composites, due to its inherent antibacterial property, biodegradability, eco-friendliness, and good thermal and mechanical characteristics. However, PLA has certain demerits such as poor water and gas barrier properties, and low glass transition temperature, which restricts its use in food packaging applications. To overcome this, PLA is blended with polysaccharides such as gum and cellulose to enhance the water barrier, thermal, crystallization, degradability, and mechanical properties. Moreover, the addition of these polysaccharides not only reduces the production cost but also helps in manufacturing packaging material with superior quality. Hence this review focuses on various fabrication techniques, degradation of the ternary composite, and its application in the food sector. Moreover, this review discusses the enhanced barrier and mechanical properties of the ternary blend packaging material. Incorporation of gum enhanced flexibility, while the reinforcement of cellulose improved the structural integrity of the ternary composite. The unique properties of this ternary composite make it suitable for extending the shelf life of food packaging, specifically for fruits, vegetables, and fried products. Future studies must be conducted to investigate the optimization of formulations for specific food types, explore scalability for industrial applications, and integrate these composites with emerging technologies (3D/4D printing).

Preparation and characterization of a novel high barrier mulching film with tunicate cellulose nanocrystals/sodium alginate/alkali lignin

In this study, the base film (CSL) was prepared by blending tunicate cellulose nanocrystals (TCNCs) extracted from tunicate shells, with sodium alginate (SA) and alkali lignin (AL). Then, the mulching film (CSL-WK) was prepared using water-borne polyurethane (WPU) as binder to install low-energy Kaolin on the surface of CSL film. The influences of composition with different concentrations on mechanical properties were studied. The tensile strength and elongation at break of CSL-WK film could reach 86.58 MPa and 50.49 %, respectively. The mulching films were characterized by degradability test, SEM, FTIR, and TGA. TCNCs had good compatibility with SA and AL, and a rough structure was formed on the surface of the film to improve the hydrophobicity. The barrier properties, including ultraviolet resistance, water contact angle, water vapor permeability, water retention, and flame retardancy, were tested. The results showed that CSL-WK films could block 97 % of ultraviolet light, reduce about 25 % of soil water loss, and self-extinguish within 7 s of open flame ignition. Note that the secondary spraying method significantly improved the barrier property of films. This study lays a foundation for the preparation of ecologically friendly, biodegradable, and high barrier mulching film, and expands the application of marine resources.

Exopolysaccharide riclin and anthocyanin-based composite colorimetric indicator film for food freshness monitoring

Food freshness monitoring is vital to ensure food safety. Recently, packaging materials incorporating pH-sensitive films have been employed to monitor the freshness of food products in real time. The film-forming matrix of the pH-sensitive film is essential to maintain the desired physicochemical functions of the packaging. Conventional film-forming matrices, such as polyvinyl alcohol (PVA), have drawbacks of low water resistance, poor mechanical properties, and weak antioxidant ability. In this study, we successfully synthesise PVA/riclin (P/R) biodegradable polymer films to overcome these limitations. The films feature riclin, an agrobacterium-derived exopolysaccharide. The uniformly dispersed riclin conferred outstanding antioxidant activity to the PVA film and significantly improved its tensile strength and barrier properties by forming hydrogen bonds. Purple sweet potato anthocyanin (PSPA) was used as a pH indicator. The intelligent film with added PSPA provided robust surveillance of volatile ammonia and changed its color within 30 s in the pH range of 2-12. This multifunctional colorimetric film also engendered discernible color changes when the quality of shrimp deteriorated, demonstrating its great potential as an intelligent packaging material to monitor food freshness.

Preparation, compatibility and barrier properties of attapulgite/poly (lactic acid)/thermoplastic starch composites

In this study, AT (attapulgite)/PLA/TPS biocomposites and films were prepared by melt blending technique using PLA and TPS as matrix, polyethylene glycol (PEG) as plasticizing modifier of PLA and AT clay as additive. The effect of AT content on the performance of AT/PLA/TPS composites was investigated. The results showed that, as the AT concentration increased, the fracture surface of the composite showed a bicontinuous phase structure when the AT content was 3 wt%. The rheological properties showed that the addition of AT resulted in more significant deformation of the minor phase, which reduced the phase size and led to lower complex viscosity, and more processability from the industrial perspective. The mechanical properties showed that the addition of AT nanoparticles could simultaneously improve the tensile strength and elongation at break of the composites, reaching a maximum at 3 wt% load. The water vapor barrier performance results showed that AT significantly improved the WVP of the film, and the moisture resistance performance was increased by 254 % compared with the PLA/TPS composite film within 5 h. In conclusion, the obtained AT/PLA/TPS biocomposites showed potential in packaging engineering and injection molding products, especially when renewability and full biodegradability of the material are required.

Preparation of robust and fully bio-based modified paper via mussel-inspired layer-by-layer assembly of chitosan and carboxymethyl cellulose for food packaging

A green and facile method was proposed to prepare robust and fully bio-based modified paper in this study, which involved in layer-by-layer deposition of chitosan (CS) and mussel adhesive protein-mimetic polymer (dopamine-grafted carboxymethyl cellulose, CMC-g-DA) on paper surface and subsequent oxidative cross-linking by sodium periodate. The mechanical, barrier and antibacterial properties of the cross-linked multilayer-modified paper significantly improved with the increased bilayer numbers. Compared with unmodified paper, cross-linked (CS/CMC-g-DA)₆ multilayer-modified paper exhibited 71.6 % improvement in tensile strength, 69.2 % and 56.3 % decline in air and water vapor permeability, as well as above 90 % antibacterial efficiency against S. aureus and E. coli. Particularly, the cross-linked multilayer-modified paper maintained outstanding functional stability even after suffering from vigorously corrosive treatment. The obtained functional paper effectively extended the shelf-life of Agaricus bisporus to 6 days under ambient conditions. We believed that the prepared robust functional paper in this study will have promising application prospect in food packaging field.

Functionalized cellulose nanocrystal embedded into citrus pectin coating improves its barrier, antioxidant properties and potential application in food

Due to the hydrophilic of the pectin material, the coating has poor barrier properties and a negative preservation effect on fresh fruits. In this study, citrus pectin coating with improved barrier and antioxidant properties was prepared by embedding with functional cellulose nanocrystals (CNC). It was assessed that cellulose nanocrystals grafted with p-coumaric acid (CNC-P) were uniformly dispersed in the pectin matrix to improve coating barrier properties. The addition of 8 % CNC-P to the pectin coating led to a decrease in water vapor and oxygen permeability from the coating by 12.6 % and 22.3 %, respectively. Additionally, the grafted p-coumaric acid (PA) introduced antioxidant properties to the cellulose nanocrystals. The fresh-cut fruits preservation assay showed that the coating containing CNC-P exerted a stronger inhibition effect of the browning process within 8 h than other coatings. This study suggests that pectin coating embedded with CNC-P has the potential to be used in food packaging.

Engineering cellulose nanopaper with water resistant, antibacterial, and improved barrier properties by impregnation of chitosan and the followed halogenation

This work demonstrated a facile and sustainable approach to functionalize cellulose nanopaper (CNP) by impregnation of chitosan (CS) and the followed halogenation. It was found that the tensile strength of the functionalized CNP (CNP/CS-Cl) was enhanced by 38.3% and 512.6% at dry and wet conditions, respectively. Meanwhile, the total transmittance (at 550 nm) of CNP/CS-Cl was increased from 75% of pure CNP to 85%, with 35% decrease in optical haze. Moreover, the CNP/CS-Cl exhibited significant enhancement in barrier properties. Importantly, part of the amino groups on CS were transformed into N-halamines during the halogenation process, which endowed the CNP/CS-Cl with excellent antibacterial performance against both S. aureus and E. coli with 100% bacterial reduction after 10 min of contact. Thus, this work provides a simple and efficient approach to functionalize CNP with water resistance, high transparency, excellent antibacterial and barrier properties, which will expand the potential applications of CNP.

Development and characterization of a novel edible film based on Althaea rosea flower gum: Investigating the reinforcing effects of bacterial nanocrystalline cellulose

Althaea rosea flowers were used to procure the gum (ARG) needed for film preparation. Pretest studies suggested 1.5% ARG + 50% glycerol as optimum for film preparation. The reinforcement impact of 3, 5, and 8 wt% bacterial nanocrystalline cellulose (BNC) incorporation (based on the dry weight of ARG) was investigated on the structural, mechanical, physical, thermal, optical, morphological, and barrier properties of films. The Results suggested that increasing the BNC concentration until a certain level (5 wt% BNC) could improve the latter properties. However, at higher concentration (8 wt% BNC), cellulose nanoparticles tended to agglomerate, which led to the impairment of some of those properties, especially barrier properties. According to AFM and SEM results, BNC addition increased surface roughness and coarseness. All BNC-loaded films showed better functions compared to control sample (0 wt% BNC) and the film containing 5 wt% BNC was suggested as the optimum film.

Developing chitin nanocrystals for flexible packaging coatings

This study assessed the applicability of chitin nanocrystals employed in combination with an existing coating material intended for flexible packaging. The 2,2,6,6-tetramethylpiperidine 1-oxyl (TEMPO) oxidized chitin nanocrystals (TOCNs) were applied 1) as an additive in a water-based acrylic resin (WBAR) that was then coated onto the surface of a biaxially oriented polypropylene (BOPP) film, and 2) as a neat layer in multilayered BOPP laminates bonded by a WBAR adhesive layer. The results indicated that the flow behavior and shear viscosity of the TOCN/WBAR system were dependent on TOCN contents. The TOCNs as a dispersed phase in the acrylic resin matrix did not improve the oxygen barrier property of the resulting coated BOPP. By contrast, the neat continuous TOCN coating layer improved the oxygen barrier property of the laminates of BOPP and TOCNs bonded by the acrylic resin, a 44% oxygen transmission rate reduction for a laminate with a 8.33-μm TOCN layer compared to the laminate without a TOCN layer. The inclusion of the TOCNs maintained the optical transparency of the resulting films.

Polylactic acid/zinc oxide biocomposite films for food packaging application

Although PLA is much more expensive than polyolefins, such as PP and PE, there is a great interest to propose PLA based material as alternative films for food packaging being PLA derivable from natural source, compostable and biodegradable. For this purpose the research has the task to investigate and propose PLA materials with enhanced properties to be effectively and efficiently alternative to polyolefin films for food packaging application. In this contribution, biocomposite films of PLA with 1, 3 and 5wt% of ZnO have been investigated to determine mechanical, barrier and antimicrobial (against Escherichia coli) properties. It is found that the biocomposite films are characterized by a good dispersion of the ZnO particles in PLA matrix, although no previous treatment was performed on ZnO particles, such as silanization, to decrease its incompatibility with the polymer. The biocomposite films have shown good mechanical properties, decrease of permeability to CO2 and O2, and only a slight increase to water vapour. Particularly important is that, for the biocomposite with 5wt% of ZnO, the % Reduction for E. Coli test reached the value of 99.99 already after 24h.