Thermo-/pH-responsive preservative delivery based on TEMPO cellulose nanofiber/cationic copolymer hydrogel film in fruit packaging

Current progress in functionalization of cellulose nanofibers (CNFs) for active food packaging

There is a growing interest in utilizing renewable biomass resources to manufacture environmentally friendly active food packaging, against the petroleum-based polymers. Cellulose nanofibers (CNFs) have received significant attention recently due to their sustainability, biodegradability, and widely available sources. CNFs are generally obtained through chemical or physical treatment, wherein the original surface chemistry and interfacial interactions can be changed if the functionalization process is applied. This review focuses on promising and sustainable methods of functionalization to broaden the potential uses of CNFs in active food packaging. Novel aspects, including functionalization before, during and after cellulose isolation, and functionalization during and after material processing are addressed. The CNF-involved structural construction including films, membranes, hydrogels, aerogels, foams, and microcapsules, is illustrated, which enables to explore the correlations between structure and performance in active food packaging. Additionally, the enhancement of CNFs on multiple properties of active food packaging are discussed, in which the interaction between active packaging systems and encapsulated food or the internal environment are highlighted. This review emphasizes novel approaches and emerging trends that have the potential to revolutionize the field, paving the way for advancements in the properties and applications of CNF-involved active food packaging.

Recent advances in TEMPO-oxidized cellulose nanofibers: Oxidation mechanism, characterization, properties and applications

Cellulose is the richest renewable polymer source on the earth. TEMPO-mediated oxidized cellulose nanofibers are deduced from enormously available wood biomass and functionalized with carboxyl groups. The preparation procedure of TOCNFs is more environmentally friendly compared to other cellulose, for example, MFC and CNCs. Due to the presence of functional carboxyl groups, TOCNF-based materials have been studied widely in different fields, including biomedicine, wastewater treatment, bioelectronics and others. In this review, the TEMPO oxidation mechanism, the properties and applications of TOCNFs are elaborated. Most importantly, the recent advanced applications and the beneficial role of TOCNFs in the various abovementioned fields are discussed. Furthermore, the performances and research progress on the fabrication of TOCNFs are summarized. It is expected that this timely review will help further research on the invention of novel material from TOCNFs and its applications in different advanced fields, including biomedicine, bioelectronics, wastewater treatment, and the energy sector.

Assessing the Safety of Mechanically Fibrillated Cellulose Nanofibers (fib-CNF) via Toxicity Tests on Mice: Single Intratracheal Administration and 28 Days' Oral Intake

Mechanically fibrillated cellulose nanofibers, known as fib-CNF (fiber length: 500 nm; diameter: 45 nm), are used in composites and as a natural thickener in foods. To evaluate their safety, we conducted a 28-day study in mice with inhalation exposure at 0.2 mg/body and oral administration of 400 mg/kg/day. Inhalation exposure to fib-CNF caused transient weight loss, changes in blood cell counts, and increased lung weights. These changes were attributed to adaptive responses. The oral administration of fib-CNF for 28 days resulted in no apparent toxic effects except for a slight decrease in platelet counts. The fib-CNF administration using the protocols studied appears to be safe in mice.

Recent Progress in Stimuli-Responsive Antimicrobial Electrospun Nanofibers

Electrospun nanofibrous membranes have garnered significant attention in antimicrobial applications, owing to their intricate three-dimensional network that confers an interconnected porous structure, high specific surface area, and tunable physicochemical properties, as well as their notable capacity for loading and sustained release of antimicrobial agents. Tailoring polymer or hybrid-based nanofibrous membranes with stimuli-responsive characteristics further enhances their versatility, enabling them to exhibit broad-spectrum or specific activity against diverse microorganisms. In this review, we elucidate the pivotal advancements achieved in the realm of stimuli-responsive antimicrobial electrospun nanofibers operating by light, temperature, pH, humidity, and electric field, among others. We provide a concise introduction to the strategies employed to design smart electrospun nanofibers with antimicrobial properties. The core section of our review spotlights recent progress in electrospun nanofiber-based systems triggered by single- and multi-stimuli. Within each stimulus category, we explore recent examples of nanofibers based on different polymers and antimicrobial agents. Finally, we delve into the constraints and future directions of stimuli-responsive nanofibrous materials, paving the way for their wider application spectrum and catalyzing progress toward industrial utilization.

Sustainable polysaccharide and protein hydrogel-based packaging materials for food products: A review

Sustainable food packaging is a necessary element to ensure the success of a food system, the accomplishment of which is weighed in terms of quality retention and ensured products safety. Irrespective of the raised environmental concerns regarding petroleum-based packaging materials, a sustainable analysis and a lab to land assessment should be a priority to eliminate similar fates of new material. Functionalized bio-based hydrogels are one of the smartest packaging inventions that are expected to revolutionize the food packaging industry. Although in this review, the focus relies on recent developments in the sustainable bio-based hydrogel packaging materials, natural biopolymers such as proteins and polysaccharides from which hydrogels could be obtained, the challenges encountered in hydrogel-based packaging materials and the future prospects of hydrogel-based food packaging materials are also discussed. Moreover, the need for 'Life Cycle Assessment' (LCA), stress on certifications and a sustainable waste management system is also suggested which can bring both food and packaging into the same recycling bins.

Facile Fabrication of Anthocyanin-Nanocellulose Hydrogel Indicator Label for Intelligent Evaluation of Minced Pork Freshness

In order to develop a reliable and rapid method for meat freshness detection, nanocellulose (TOCNF) prepared via the TEMPO (2,2,6,6-tetramethylpiperidine oxidation) oxidation method was used as raw material to prepare hydrogels using Zn²⁺ coordination and binding. Physicochemical properties such as water absorption and porosity were analyzed. It was further used to select suitable hydrogels for the preparation of indication labels after anthocyanin adsorption, and it was applied in the freshness detection of fresh minced pork. Five percent TOCNF (w/w) aqueous solution was homogenized by high shear for 4 min, and 20% (w/w) zinc chloride solution was added to it, so that the concentration of zinc ions could reach 0.25 mol/L. After standing for 24 h, the hydrogel was obtained with good water absorption and a porous three-dimensional network structure. The activation energies of volatile base nitrogen (TVBN) and anthocyanin indicating label color changes were 59.231 kJ/mol and 69.453 kJ/mol, respectively. The difference between the two is within 25 kJ/mol, so the prepared indicator label can accurately visualize the shelf life of fresh pork.

State-of-the-Art Insights and Potential Applications of Cellulose-Based Hydrogels in Food Packaging: Advances towards Sustainable Trends

Leveraging sustainable packaging resources in the circular economy framework has gained significant attention in recent years as a means of minimizing waste and mitigating the negative environmental impact of packaging materials. In line with this progression, bio-based hydrogels are being explored for their potential application in a variety of fields including food packaging. Hydrogels are three-dimensional, hydrophilic networks composed of a variety of polymeric materials linked by chemical (covalent bonds) or physical (non-covalent interactions) cross-linking. The unique hydrophilic nature of hydrogels provides a promising solution for food packaging systems, specifically in regulating moisture levels and serving as carriers for bioactive substances, which can greatly affect the shelf life of food products. In essence, the synthesis of cellulose-based hydrogels (CBHs) from cellulose and its derivatives has resulted in hydrogels with several appealing features such as flexibility, water absorption, swelling capacity, biocompatibility, biodegradability, stimuli sensitivity, and cost-effectiveness. Therefore, this review provides an overview of the most recent trends and applications of CBHs in the food packaging sector including CBH sources, processing methods, and crosslinking methods for developing hydrogels through physical, chemical, and polymerization. Finally, the recent advancements in CBHs, which are being utilized as hydrogel films, coatings, and indicators for food packaging applications, are discussed in detail. These developments have great potential in creating sustainable packaging systems.

On the mechanism of enhanced foam stability by combining carboxylated cellulose nanofiber with hydrocarbon and fluorocarbon surfactants

The effect of carboxylated cellulose nanofiber (CCNF) on the firefighting foam stability and stabilization mechanism is investigated. The results show that equilibrium surface tension of CTAB/FC1157 solution decreases when CCNF concentration increases to 0.5 wt%, while CCNF has little effect on that of SDS/FC1157 solution. Besides, when CCNF concentration of SDS/FC1157 solution increases to 1.0 wt%, the foam initial drainage is delayed for about 3 min. Increasing CCNF concentration can slow down foam coarsening process and liquid drainage process of SDS/FC1157 and CTAB/FC1157 solutions, improving the foam stability. The foam stability enhancement of CTAB/FC1157 solution is due to the formation of bulk aggregates and the increase of viscosity. However, the foam stability enhancement of SDS/FC1157 solution may be caused by the increase of viscosity. CCNF significantly reduces the foaming ability of CTAB/FC1157 solution when CCNF concentration is >0.5 wt%. Nevertheless, the foaming ability of SDS/FC1157 solution decreases significantly when CCNF concentration reaches 3.0 wt%, and its foaming ability remains higher than CTAB/FC1157 solution. The foaming ability of SDS/FC1157 solution is mainly dominated by viscosity, while that of CTAB/FC1157 solution is dominated by viscosity and adsorption kinetics. Adding CCNF is expected to enhance the stability of firefighting foam and increase the efficiency of extinguishing fire.

High-Release, Residue-Free Polysaccharide Hydrogel for Refrigerated Food Preservation

Hundreds of millions of tons of food resources are wasted annually due to microbial contamination. Effective food packaging can prevent food contamination and wastage. However, traditional food packaging has the problem of low release of bioactive substances. This study aimed to prepare a pH-responsive polysaccharide hydrogel (GDPP) by double cross-linking of ester and hydrogen bonds that could result in a high release of bioactive substances and no residual peeling. The infrared results showed the existence of ester bonds in the hydrogel, and the scanning electron microscopy results showed the porous network structure of the hydrogel. The results of texture profile analysis and self-healing tests showed that GDPP-1 has good mechanical and self-healing properties. Moreover, the ester bond of the hydrogel broke in response to the pH in the environment, improving the swelling and release properties of the hydrogel. The equilibrium swelling ratio of GDPP-1 was greater than 1000%, and the release rate of bioactive substances was more than 80%. Notably, the results of peeling experiments showed that only 0.1 N external force was needed to separate the hydrogel from the salmon, and no residue was observed on the salmon surface. The final freshness test results showed that the hydrogel effectively prolonged the shelf life of refrigerated salmon for 3-6 days. These findings indicated that hydrogels could be used in food packaging to extend the shelf life of refrigerated food. Furthermore, their advantages of low cost and simple preparation can better meet the needs of food industry applications.

Binary Hydrogels: Induction Methods and Recent Application Progress as Food Matrices for Bioactive Compounds Delivery-A Bibliometric Review

Food hydrogels are biopolymeric materials made from food-grade biopolymers with gelling properties (proteins and polysaccharides) and a 3D network capable of incorporating large amounts of water. They have sparked considerable interest because of their potential and broad application range in the biomedical and pharmaceutical sectors. However, hydrogel research in the field of food science is still limited. This knowledge gap provides numerous opportunities for implementing their unique properties, such as high water-holding capacity, moderated texture, compatibility with other substances, cell biocompatibility, biodegradability, and high resemblance to living tissues, for the development of novel, functional food matrices. For that reason, this article includes a bibliometric analysis characterizing research trends in food protein-polysaccharide hydrogels (over the last ten years). Additionally, it characterizes the most recent developments in hydrogel induction methods and the most recent application progress of hydrogels as food matrices as carriers for the targeted delivery of bioactive compounds. Finally, this article provides a future perspective on the need to evaluate the feasibility of using plant-based proteins and polysaccharides to develop food matrices that protect nutrients, including bioactive substances, throughout processing, storage, and digestion until they reach the specific targeted area of the digestive system.

Two-dimensional lamellar polyimide/cardanol-based benzoxazine copper polymer composite coatings with excellent anti-corrosion performance

The economic loss and environmental damage caused by metal corrosion is irreversible. Thus, effective methods, such as coating technologies are used to protect metal surfaces from corrosion. In this work, cardanol-based benzoxazine (CB) was synthesized by a solvent-free method using cardanol, paraformaldehyde and n-octylamine. A cardanol-based benzoxazine copper polymer (CBCP) with good mechanical properties was then prepared by CuCl₂ catalysis and can be cured at room temperature. Subsequently, polyimide corrosion inhibitors with a two-dimensional sheet structure (pyromellitic dianhydride polyimide (PDPI) and 1,4,5,8-naphthalene tetracarboxylic dianhydride polyimide (NDPI)) were designed and prepared. Lastly, PDPI or NDPI was mixed with CBCP to obtain two-dimensional lamellar polyimide/cardanol-based benzoxazine copper polymer composite coatings. The Tafel curves and electrochemical impedance spectroscopy (EIS) measurements showed composite coatings with good corrosion resistance in different corrosive media. Compared to CBCP coating, the anticorrosion performance of the composite coatings improved obviously, especially the coating obtained with 0.5 wt% PDPI. It exhibits a high polarization resistance (3.874 × 10⁹ Ω), a high protection efficiency (99.99% and 97.98%) and low corrosion rate (3.376 × 10⁻⁶ mm year⁻¹). This work suggested a facile and eco-friendly strategy for preparing bio-based anticorrosive composite coatings from low cost and abundant cardanol and polyimide corrosion inhibitors, which will significantly promote their application in metal anticorrosion.

Room temperature cured two-dimensional lamellar polyimide/cardanol-based benzoxazine copper polymer composite coatings were successfully prepared, which exhibited excellent mechanical properties and anticorrosion properties.