Multilayer surface construction for enhancing barrier properties of cellulose-based packaging

Functional barrier and recyclable packaging materials through microfibrillated cellulose bilayer composite coatings

Although microfibrillated cellulose (MFC) offers high barrier properties against air, oxygen, and oil, its limited water resistance restricts industrial applications. An innovative bilayer composite coating (BCC) has therefore been developed in response, consisting of a top layer providing water resistance and the MFC layer contributing to the gas & oil barrier and recyclability. The top coating integrates styrene-butadiene copolymer for its non-polar characteristics and nanoclay to create a hydrophobic surface that resists moisture with enhanced tortuosity. Scanning electron microscopy confirmed a stable interface between the paper substrate and the BCC. X-ray photoelectron spectroscopy (XPS) and Time-of-Flight Secondary Ion Mass Spectroscopy (ToF-SIMS) show that the BCC prevents intermixing between layers, enhancing barrier performance and fiber recovery with reduced stickies during recycling. The BCC significantly improved barrier properties, achieving a 56 % reduction in water vapor transmission rate, a ∼ 630-fold decrease in air permeability, an oil & grease resistance of kit rating 12, and < 5 % weight gain from the hot oil test. These improvements highlight the efficacy of the BCC system for enhanced barrier and recyclability, especially in stickies reduction. This research demonstrates that the strategic combination of conventional and novel MFC materials can provide sustainable packaging with functional barriers and recyclability for a circular economy.

Development of multifunctional quaternary ammonium cellulose coating for fruit preservation

Due to the lack of preservation technology and cold chain logistics, the decay loss rate of fruits and vegetables is surprisingly high. To meet the demands of environmental protection and food preservation, sustainable coating materials that fabricated by biowaste to wealth approach can efficiently cover the challenges. Hence, quaternary ammonium lotus root residue celluloses (QACs) were homogeneously synthesized by reacting cellulose with 3-chloro-2-hydroxypropyltrimethylammonium chloride for 24 h. In terms of the chemical structure, morphology, rheological property and biocompatibility as well as antimicrobial ability, QACs were characterized. The antibacterial mechanism was investigated at cellular level via disruption of membrane integrity, metabolic inactivation, destruction of antioxidant system. Meanwhile, due to the nature source of cellulose, QACs exhibited inherent outstanding biocompatibility. QACs could extend preservation time of strawberry for least 3 d by decreasing the weight loss and maintaining the hardness and springiness, as well as inhibit the growth of pathogenic bacteria. The residual amount of QACs coating on the surface of strawberries was <0.1 mg kg-1, featuring with easy cleaning and safety. This biowaste-derived coating for strawberry preservation not only provides a new strategy for fruit preservation platforms but also expands the high-value application of biowaste resources in the agro-industry.

Development of hydrophobic sodium carboxymethyl cellulose/polyvinyl alcohol/chitosan paper-based antimicrobial indicator cards based on a non-fluorinated silane coating for monitoring carp freshness

The United Nations Sustainable Development Goals (SDGs) have led to a notable increase in the use of paper-based packaging. But the poor water resistance significantly limits the application scenarios for paper-based packaging. This study was designed to improve the hydrophobic properties of paper-based antimicrobial indicator cards by surface coating with methyltrichlorosilane (MTS) and octadecyltrichlorosilane (OTS). The results indicated that all treated antimicrobial indicator cards changed from hydrophilic to hydrophobic, with the MTS/OTS (1:1) treated antimicrobial indicator cards (M/OTS@Paper) showing the highest hydrophobicity (119.38°) and strong hydrophobic stability. Fourier-transform infrared spectroscopy (FT-IR) analysis indicated that the increase in hydrophobicity was attributable to the decrease in hydrogen bonding within the hydroxyl groups. X-ray diffraction (XRD) results substantiated that the hydroxyl groups present in the paper and polyvinyl alcohol (PVA) reacted with the hydrophobicizing agent, which was consistent with the phenomenon observed in scanning electron microscope (SEM). The hydrophobically treated antimicrobial indicator cards showed varying degrees of mechanical degradation due to hydrogen bond disruption. Antimicrobial indicator cards still retain excellent antimicrobial activity, pH response, and ammonia sensitivity after hydrophobic treatment. When using the antimicrobial indicator cards to monitor carp freshness, the cards' color changed significantly from purple-red to purple-black, and the fish's shelf life was extended by 2 days compared to the control group without antimicrobial indicator card. According to the comprehensive evaluation, M/OTS@Paper has the best hydrophobicity and has good application prospects in freshness indication packaging.

Streamlining electrospun shellac coatings on paper for high moisture strength and barrier food packaging film: Tailoring the processing parameters for accelerated coating

Coated paper with bio-based components has sparked attention as a food packaging alternative to plastic. This study focusses on development of environmentally friendly packaging solution by electrospraying shellac over paper's surface. The goal of the study is to reduce the time of fabrication, by optimising the process parameters, concentration; 20, 30, and 40%w/v, flow rate; 10, 20, and 30 ml/h, and coating time; 100, 200, and 300 s (Concentration (% w/v))/ Flow rate (ml/h)/ time (sec)), in order to get better GSM (grams per square meter), COBB (grams of water absorbed per square meter), KIT (oil resistance ability), and WVTR (water vapor transmission rate). The developed material shows tensile strength >20 MPa with a 90 % drop in water absorption. Furthermore, when exposed to 100 % relative humidity for 48 h, the sample absorbs only 7-9 % moisture and showing minimal reduction in tensile strength of 3-5 %, indicating superior moisture resistance compared to paper. Cherry tomato (CT) freshness was tested and found to be maintained for up to 28 days, which was comparable to polyethylene packaging with mass loss during storage of 7, 4, and 20 %, respectively. In 28 days, the developed films decomposed similarly to paper in soil (23.67 %) and water (5.44 %), with no significant change in quality of water.

The potential of nanofibrillated cellulose from Hevea brasiliensis to produce films for bio-based packaging

Cellulose micro/nanofibril (MNFC) films are an interesting alternative to plastic-based films for application in biodegradable packaging. In this study, we aimed to produce and characterize MNFC films obtained from alkaline-pretreated rubberwood (Hevea brasiliensis) waste and Eucalyptus sp. commercial pulp. MNFC and films were evaluated regarding microstructure; crystallinity; stability; and physical, optical, mechanical, and barrier properties. A combined quality index (QI) was also calculated. Eucalyptus MNFC suspensions were more stable than H. brasiliensis. Both films had a hydrophobic surface (>90°) and high grease resistance (oil kit 12). H. brasiliensis films had lower transparency (26.4 %) and high crystallinity (∼89 %), while Eucalyptus films had lower permeability and higher mechanical strength. The QI of MNFC was 51 ± 5 for H. brasiliensis and 55 ± 4 for Eucalyptus, showing that both types of raw material have potential for application in the packaging industry and in the reinforcement of composites, as well as for high value-added applications in products made from special materials.

Cellulose nanocrystals in the development of biodegradable materials: A review on CNC resources, modification, and their hybridization

The escalating demand for sustainable materials has propelled cellulose into the spotlight as a promising alternative to petroleum-based products. As the most abundant organic polymer on Earth, cellulose is ubiquitous, found in plants, bacteria, and even a unique marine animal-the tunicate. Cellulose polymers naturally give rise to microscale semi-crystalline fibers and nanoscale crystalline regions known as cellulose nanocrystals (CNCs). Exhibiting rod-like structures with widths spanning 3 to 50 nm and lengths ranging from 50 nm to several microns, CNC characteristics vary based on the cellulose source. The degree of crystallinity, crucial for CNC properties, fluctuates between 49 and 95 % depending on the source and synthesis method. CNCs, with their exceptional properties such as high aspect ratio, relatively low density (≈1.6 g cm-3), high axial elastic modulus (≈150 GPa), significant tensile strength, and birefringence, emerge as ideal candidates for biodegradable fillers in nanocomposites and functional materials. The percolation threshold, a mathematical concept defining long-range connectivity between filler and polymer, governs the effectiveness of reinforcement in nanocomposites. This threshold is intricately influenced by the aspect ratio and molecular interaction strength, impacting CNC performance in polymeric and pure nanocomposite materials. This comprehensive review explores diverse aspects of CNCs, encompassing their derivation from various sources, methods of modification (both physical and chemical), and hybridization with heterogeneous fillers. Special attention is devoted to the hybridization of CNCs derived from tunicates (TCNC) with those from wood (WCNC), leveraging the distinct advantages of each. The overarching objective is to demonstrate how this hybridization strategy mitigates the limitations of WCNC in composite materials, offering improved interaction and enhanced percolation. This, in turn, is anticipated to elevate the reinforcing effects and pave the way for the development of nanocomposites with tunable viscoelastic, physicochemical, and mechanical properties.

Enhancing Paper Packaging's Wet Strength Using the Synergy between Chitosan and Nanofibrillated Cellulose Additives

The demand for eco-friendly packaging materials has urged researchers to look for alternatives to petroleum-based polymers. In this regard, paper-based products have turned out to be a promising choice; however, their weak resistance to water has limited their application. The use of various additives to enhance paper's moisture resistance is a common practice. However, considering the growing global agenda for sustainable development, the search for new bio-based paper additives has become increasingly important. This study investigated the potential synergistic impact of the addition of nanofibrillated cellulose (NFC) and chitosan additives (CHIT) to different fiber combinations to improve paper's properties, in particular, their wet strength. The efficacy of the additive application order was examined and was found to be crucial in achieving the desired outcomes. The results showed that incorporating CHIT after NFC enhanced the paper's tensile and burst indicators, as well as the paper stretch in the dry state, by 35-70%, 35-55%, and 20-35%, respectively. In addition, the tensile index and stretch in the wet state improved 9-13 times and 2.5-5.5 times over, respectively. The air permeability decreased 2.5-12 times over. These findings demonstrate that the sequential addition of the NFC and CHIT additives yield a greater enhancement of paper's properties than using each additive separately.

Robust and versatile superhydrophobic cellulose-based composite film with superior UV shielding and heat-barrier performances for sustainable packaging

Replacing single-use plastic delivery bags (SPDBs) with cellulose-based materials is an effective strategy to reduce environmental pollution. However, the inherent hydrophilicity and ultralow mechanical strength of cellulose materials limit its development. In this study, zinc oxide (ZnO)-cellulose composite films were successfully prepared through "two-step strategy" of lotus leaves structure simulation, including deposition of micro-nano ZnO particles and stearic acid (STA) modification. Well-dispersed micro-nano ZnO particles with stick-like structure were anchored in the ZnO-cellulose composite film prepared at 90 °C (CF-90). Due to the special structural design and strong interaction between the cellulose and micro-nano ZnO particles, the CF-90 showed higher mechanical property (a 47.8 % improvement in the tensile strength). Impressively, CF-90 also exhibited great UV shielding properties with larger UPF value of 1603.98 and superhigh heat-barrier performance. Moreover, CF-90 obtained excellent superhydrophobicity with a water contact angle of 163.6° by further modification. Consequently, the versatile cellulose-based material bringing a dawn on application of sustainable packaging materials for express delivery industry.

Development and characterization of novel emulsified nanocomposite coatings incorporating different loadings of nanoclay and beeswax for paper packaging

Paper coated with poly (vinyl alcohol) (PVA)-based films incorporating varying amounts of halloysite nanotubes (HNTs) and/or beeswax (BW) were developed. The applied PVA/HNTs nanocomposite films, PVA/BW emulsified films, and PVA/HNTs/BW emulsified nanocomposite films were characterized in terms of FTIR, TGA, DSC, and XRD analyses. The effects of HNTs and/or BW at different loadings on the functional properties of coated paper were investigated. HNTs and BW co-incorporation significantly improved the water vapor permeability of the resulting PVA/HNTs/BW coated paper samples, and reduced their Cobb60 values, respectively, by more than 50, 24, and 18% as compared to the uncoated paper, paper coated with pristine PVA and paper coated with PVA/HNTs nanocomposite-based coatings. While increasing their contact angle values in the range of 10-20%. Likewise, HNTs and BW co-incorporation increased the mechanical strength of PVA/HNTs/BW coated paper in the range of 20.54-29.80% as compared to the uncoated paper, while increasing their flexibility up to 32.50%. Such enhancement in the functional properties of PVA/HNTs/BW coated paper is most likely due to the establishment of interactions between PVA, BW, and HNTs. Our results demonstrate the ability of PVA/HNTs/BW emulsified nanocomposite coatings to improve paper barrier and mechanical properties owing to the prominent reinforcement effects of HNTs and the good moisture-barrier properties of BW.

Lignin self-assembly and auto-adhesion for hydrophobic cellulose/lignin composite film fabrication

Large amounts of lignin are produced as a by-product of paper pulping, resulting in a tremendous waste of natural resources with potential uses across various areas. To achieve the value-added utilization of agricultural waste and lignin, we developed a method for the fabrication of a lignin structure-designed hydrophobic film (LSHF) directly through solvent/anti-solvent self-assembly (acetic acid aqueous solution/n-hexane) and auto-adhesion of acetic acid lignin (AL) on the surface of a lignocellulose film (LCF). As the morphology structure revealed, the LSHF had a rough surface composed of lignin colloidal spheres, which significantly improved the water contact angle (WCA) from ~80° to ~130°. Furthermore, benefiting from the auto-adhesion of lignin, the WCA was more stable in 240 s, demonstrating that the LSHF had a lower WCA decrease (15.53 % - 25.55 % decrease) than the LCF (41.97 % - 61.11 % decrease) and the sample without auto-adhesion (100 % decrease). Simultaneously, auto-adhesion endowed the LSHF with a ~50 % increase in tensile strength. This work provides a novel strategy for the fabrication of hydrophobic cellulose/lignin composite films via lignin self-assembly and auto-adhesion.

Biodegradable Nanofibrillated Cellulose/Poly-(butylene adipate-co-terephthalate) Composite Film with Enhanced Barrier Properties for Food Packaging

Biodegradable composites consisting of Poly-(butylene adipate-co-terephthalate) (PBAT), thermoplastic starch, hydrophobically modified nanofibrillated cellulose (HMNC), and green surfactant (sucrose fatty acid ester) were prepared via the melt-mixing and film-blowing process (PBAT-HMNC). The composites were characterized using the Fourier transform infrared spectroscope (FT-IR), scanning electron microscope (SEM), and thermogravimetric analyzer (TGA). The mechanical and barrier properties were systematically studied. The results indicated that PBAT-HMNC composites exhibited excellent mechanical and barrier properties. The tensile strength reached the maximum value (over 13 MPa) when the HMNC content was 0.6% and the thermal decomposition temperature decreased by 1 to 2 °C. The lowest values of the water vapor transmission rate (WVTR) and the oxygen transmission rate (OTR) were obtained from the composite with 0.6 wt% HMNC, prepared via the film-bowing process with the values of 389 g/(m2·day) and 782 cc/(m2·day), which decreased by 51.3% and 42.1%, respectively. The Agaricus mushrooms still had a commodity value after 11 days of preservation using the film with 0.6 wt% HMNC. PBAT-HMNC composites have been proven to be promising nanocomposite materials for packaging.

Solventless Photopolymerizable Paper Coating Formulation for Packaging Applications

Nowadays, packaging applications require the use of advanced materials as well as production methods that have a low environmental impact. In this study, a solvent-free photopolymerizable paper coating was developed using two acrylic monomers (2-ethylhexyl acrylate and isobornyl methacrylate). A copolymer, with a molar ratio of 2-ethylhexyl acrylate/isobornyl methacrylate of 0.64/0.36, was prepared and used as the main component of the coating formulations (50 and 60 wt%). A mixture of the monomers with the same proportion was used as a reactive solvent, yielding formulations with 100% solids. The coated papers showed an increase in the pick-up values from 6.7 to 32 g/m² depending on the formulation used and the number of coating layers (up to two). The coated papers maintained their mechanical properties and presented improved air barrier properties (Gurley's air resistivity of ≈25 s for the higher pick-up values). All the formulations promoted a significant increase in the paper's water contact angle (all higher than 120 °) and a remarkable decrease in their water absorption (Cobb values decrease from 108 to 11 g/m²). The results confirm the potential of these solventless formulations for fabricating hydrophobic papers with potential application in packaging, following a quick, effective, and more sustainable approach.

Recent Advances in Chemically Modified Cellulose and Its Derivatives for Food Packaging Applications: A Review

The application of cellulose in the food packaging field has gained increasing attention in recent years, driven by the desire for sustainable products. Cellulose can replace petroleum-based plastics because it can be converted to biodegradable and nontoxic polymers from sustainable natural resources. These products have increasingly been used as coatings, self-standing films, and paperboards in food packaging, owing to their promising mechanical and barrier properties. However, their utilization is limited because of the high hydrophilicity of cellulose. With the presence of a large quantity of functionalities within pristine cellulose and its derivatives, these building blocks provide a unique platform for chemical modification via covalent functionalization to introduce stable and permanent functionalities to cellulose. A primary aim of chemical attachment is to reduce the probability of component leaching in wet and softened conditions and to improve the aqueous, oil, water vapor, and oxygen barriers, thereby extending its specific use in the food packaging field. However, chemical modification may affect the desirable mechanical, thermal stabilities and biodegradability exhibited by pristine cellulose. This review exhaustively reports the research progress on cellulose chemical modification techniques and prospective applications of chemically modified cellulose for use in food packaging, including active packaging.

Eco-friendly laccase and cellulase enzymes pretreatment for optimized production of high content lignin-cellulose nanofibrils

Lignin-cellulose nanofibrils (LCNF) are of attracting an increasing interest due to the benefits of maintaining the lignin in the nanomaterial composition. The production of LCNF requires considerable energy consumption, which has been suppressed employing pretreatment of biomass, in which it highlights those that employ enzymes that have the advantage of being more environmentally friendly. Some negative aspects of the presence of lignin in the fiber to obtain cellulose nanofibrils is that it can hinder the delamination of the cell wall and act as a physical barrier to the action of cellulase enzymes. This study aimed to evaluate the impact of a combined enzymatic pretreatment of laccase and endoglucanase for high content lignin LCNF production. The morphological and chemical properties, visual aspect and stability, crystallinity, mechanical properties, rheology, barrier properties and quality index were used to characterize the LCNF. The laccase loading used was efficient in modifying the lignin to facilitate the action of the endoglucanase on cellulose without causing the removal of this macromolecule. This pretreatment improved the quality of LCNF (61 ± 3 to 71 ± 2 points) with an energy saving of 42% and, therefore, this pretreatment could be suitable for industrial production for a variety of applications.

Advancements in Biodegradable Active Films for Food Packaging: Effects of Nano/Microcapsule Incorporation

Food packaging plays a fundamental role in the modern food industry as a main process to preserve the quality of food products from manufacture to consumption. New food packaging technologies are being developed that are formulated with natural compounds by substituting synthetic/chemical antimicrobial and antioxidant agents to fulfill consumers' expectations for healthy food. The strategy of incorporating natural antimicrobial compounds into food packaging structures is a recent and promising technology to reach this goal. Concepts such as "biodegradable packaging", "active packaging", and "bioactive packaging" currently guide the research and development of food packaging. However, the use of natural compounds faces some challenges, including weak stability and sensitivity to processing and storage conditions. The nano/microencapsulation of these bioactive compounds enhances their stability and controls their release. In addition, biodegradable packaging materials are gaining great attention in the face of ever-growing environmental concerns about plastic pollution. They are a sustainable, environmentally friendly, and cost-effective alternative to conventional plastic packaging materials. Ultimately, a combined formulation of nano/microencapsulated antimicrobial and antioxidant natural molecules, incorporated into a biodegradable food packaging system, offers many benefits by preventing food spoilage, extending the shelf life of food, reducing plastic and food waste, and preserving the freshness and quality of food. The main objective of this review is to illustrate the latest advances in the principal biodegradable materials used in the development of active antimicrobial and antioxidant packaging systems, as well as the most common nano/microencapsulated active natural agents incorporated into these food-packaging materials.

Can Sustainable Packaging Help to Reduce Food Waste? A Status Quo Focusing Plant-Derived Polymers and Additives

The promotion of sustainable packaging is part of the European Green Deal and plays a key role in the EU’s social and political strategy. One option is the use of renewable resources and biomass waste as raw materials for polymer production. Lignocellulose biomass from annual and perennial industrial crops and agricultural residues are a major source of polysaccharides, proteins, and lignin and can also be used to obtain plant-based extracts and essential oils. Therefore, these biomasses are considered as potential substitute for fossil-based resources. Here, the status quo of bio-based polymers is discussed and evaluated in terms of properties related to packaging applications such as gas and water vapor permeability as well as mechanical properties. So far, their practical use is still restricted due to lower performance in fundamental packaging functions that directly influence food quality and safety, the length of shelf life, and thus the amount of food waste. Besides bio-based polymers, this review focuses on plant extracts as active packaging agents. Incorporating extracts of herbs, flowers, trees, and their fruits is inevitable to achieve desired material properties that are capable to prolong the food shelf life. Finally, the adoption potential of packaging based on polymers from renewable resources is discussed from a bioeconomy perspective.