Preparation of sugarcane bagasse nanocellulose hydrogel as a colourimetric freshness indicator for intelligent food packaging

Recent advances in nanocellulose based hydrogels: Preparation strategy, typical properties and food application

Nanocellulose has been favored as one of the most promising sustainable nanomaterials, due to its competitive advantages and superior performances such as hydrophilicity, renewability, biodegradability, biocompatibility, tunable surface features, excellent mechanical strength, and high specific surface area. Based on the above properties of nanocellulose and the advantages of hydrogels such as high water absorption, adsorption, porosity and structural adjustability, nanocellulose based hydrogels integrating the benefits of both have attracted extensive attention as promising materials in various fields. In this review, the main fabrication strategies of nanocellulose based hydrogels are initially discussed in terms of different crosslinking methods. Then, the typical properties of nanocellulose based hydrogels are comprehensively summarized, including porous structure, swelling ability, adsorption, mechanical, self-healing, smart response performances. Especially, relying on these properties, the general application of nanocellulose based hydrogels in food field is also discussed, mainly including food packaging, food detection, nutrient embedding delivery, 3D food printing, and enzyme immobilization. Finally, the safety of nanocellulose based hydrogel is summarized, and the current challenges and future perspectives of nanocellulose based hydrogels are put forward.

Sustainable production of cellulosic biopolymers for enhanced smart food packaging: An up-to-date review

Biodegradable and sustainable food packaging (FP) materials have gained immense global importance to reduce plastic pollution and environmental impact. Therefore, this review focused on the recent advances in biopolymers based on cellulose derivatives for FP applications. Cellulose, an abundant and renewable biopolymer, and its various derivatives, namely cellulose acetate, cellulose sulphate, nanocellulose, carboxymethyl cellulose, and methylcellulose, are explored as promising substitutes for conventional plastic in FP. These reviews focused on the production, modification processes, and properties of cellulose derivatives and highlighted their potential for their application in FP. Finally, we reviewed the effects of incorporating cellulose derivatives into film in various aspects of packaging properties, including barrier, mechanical, thermal, preservation aspects, antimicrobial, and antioxidant properties. Overall, the findings suggest that cellulose derivatives have the potential to replace conventional plastics in food packaging applications. This can contribute to reducing plastic pollution and lessening the environmental impact of food packaging materials. The review likely provides insights into the current state of research and development in this field and underscores the significance of sustainable food packaging solutions.

Ammonia/pH super-sensitive colorimetric labels based on gellan gum, sodium carboxymethyl cellulose, and dyes for monitoring freshness of lamb meat

This study aimed to develop an ammonia and pH super-sensitive label by incorporating methyl red and bromothymol blue (MR-BTB, MB) into gellan gum/sodium carboxymethyl cellulose (GG/CMC-Na, GC). Furthermore, E-nose as an auxiliary tool combined with the labels to monitor meat freshness. Results showed that MB had more color change than pure MR or BTB, and the detection limit of ammonia about the MR-BTB (1:2) group was only 2.82 ppm. The addition of MB significantly increased tensile strength, moisture content, and water solubility, but decreased elongation at break and transmittance of the GC label (p < 0.05). The result of FTIR and SEM indicated the formation of hydrogen bonds and well compatibility between MB and GC. Furthermore, the color of the GC-10.0MB label was constantly obviously changing during meat storage, indicating that the GC-10.0MB label had great potential for monitoring the freshness of the lamb meat. A high correlation was found between ΔE of GC-10.0MB label and TVB-N (R2 = 0.9092) and pH (R2 = 0.9114) of meat. Interestingly, the high correlation between ΔE of GC-10.0 MB label and the response value of S2 (R2 = 0.7531), S6 (R2 = 0.9921), and S7 sensor (R2 = 0.8325) of E-nose was also found.

Characterization and performance evaluation of colorimetric pH-sensitive indicator based on Ҡ-carrageenan/quince seed mucilage hydrogel as freshness/spoilage monitoring of rainbow trout fillet

The aim of research was to fabricate a novel indicator by using κ-carrageenan and quince seed mucilage (QSM) hydrogels and red cabbage anthocyanin. The porosity of the hydrogel was controlled using different ratios of κ-carrageenan(C):QSM(Q) (C90:Q10, C70:Q30, and C50:Q50). The hardness of hydrogels decreased from 28.6 ± 0.3 N for C90Q10 to 11.0 ± 1.0 N for C50Q50 sample. However, according to field emission scanning electron microscopy (FE-SEM) analysis, the C50R50 sample had the best morphology with smooth surface and uniform interconnected porous network. Hydrogen bonding interactions among anthocyanins, QSM, and κ-carrageenan were confirmed by Fourier transforms infrared (FT-IR) spectroscopy. The indicator showed a color variation from red to yellow over the pH range of 2-12. Also, the indicator exhibited high sensitivity to ammonia vapors (SRGB = 115%) and good color stability. The C50QRA indicator was used for monitoring rainbow trout fillet spoilage and revealed a visually-detectable color change from red to green upon detecting total volatile basic nitrogen (TVB-N) content produced throughout storage at 4 °C. Generally, the halochromic hydrogel developed in this research can be suggested as a more sensitive and accurate freshness indicator than conventional indicator solid supports.

Hydrogel-integrated sensors for food safety and quality monitoring: Fabrication strategies and emerging applications

Food safety is a global issue in public hygiene. The accurate, sensitive, and on-site detection of various food contaminants performs significant implications. However, traditional methods suffer from the time-consuming and professional operation, restricting their on-site application. Hydrogels with the merits of highly porous structure, high biocompatibility, good shape-adaptability, and stimuli-responsiveness offer a promising biomaterial to design sensors for ensuring food safety. This review describes the emerging applications of hydrogel-based sensors in food safety inspection in recent years. In particular, this study elaborates on their fabrication strategies and unique sensing mechanisms depending on whether the hydrogel is stimuli-responsive or not. Stimuli-responsive hydrogels can be integrated with various functional ligands for sensitive and convenient detection via signal amplification and transduction; while non-stimuli-responsive hydrogels are mainly used as solid-state encapsulating carriers for signal probe, nanomaterial, or cell and as conductive media. In addition, their existing challenges, future perspectives, and application prospects are discussed. These practices greatly enrich the application scenarios and improve the detection performance of hydrogel-based sensors in food safety detection.

Development of nanocellulose hydrogels for application in the food and biomedical industries: A review

As the most abundant and renewable natural resource, cellulose has attracted significant attention and research interest for the production of hydrogels (HGs). To address environmental issues and emerging demands, the benefits of naturally produced HGs include excellent mechanical properties and superior biocompatibility. HGs are three-dimensional networks created by chemical or physical cross-linking of linear or branched hydrophilic polymers and have high capacity for absorption of water and biological fluids. Although widely used in the food and biomedical fields, most HGs are not biodegradable. Nanocellulose hydrogels (NC-HGs) have been extensively applied in the food industry for detection of freshness, chemical additives, and substitutes, as well as the biomedical field for use as bioengineering scaffolds and drug delivery systems owing to structural interchangeability and stimuli-responsive properties. In this review article, the sources, structures, and preparation methods of NC-HGs are described, applications in the food and biomedical industries are summarized, and current limitations and future trends are discussed.

Cassava pomace-based biodegradable packaging materials: a review

Starch-based biodegradable packaging materials are gaining popularity as an alternative to the adverse environmental effects caused by conventional packaging materials. Despite the fact that cassava can withstand harsh environmental conditions and convert a greater quantity of solar energy into carbohydrates, its postharvest shelf life is extremely short. The preparation of cassava starch is an important method for extending the storage life of cassava. When one ton of cassava is processed, approximately 900 kg of cassava pomace, also known as cassava bagasse and cassava pulp, are produced. Due to the high residual starch and fibre content, reinforced packaging materials made from cassava pomace predominate. In the present manuscript, many possible uses of cassava pomace in packaging materials are discussed.  Furthermore, the performance attributes of packing materials assume a crucial role in the evaluation of the quality of the respective materials. The manuscript discusses various performance characteristics of packaging materials derived from cassava pomace. The features discussed include water vapour permeability, moisture content, solubility, thickness, colour, light barrier properties, mechanical properties, FT-IR analysis, thermal stability, biodegradation, contact angle, and the presence of plasticizers. Though cassava starch film has become a favourable substitute for conventional packaging materials, commercialization is limited due to having drawbacks, and the current solutions are also catalogued in this review.

Visible detection of chilled beef freshness using a paper-based colourimetric sensor array combining with deep learning algorithms

This study developed an innovative approach that combines a colourimetric sensor array (CSA) composed of twelve pH-response dyes with advanced algorithms, aiming to detect amine gases and assess the freshness of chilled beef. With the assistance of multivariate statistical analysis, the sensor array can effectively distinguish five amine gases and enable rapid quantification of trimethylamine vapour with a limit of detection (LOD) of 8.02 ppb and visually monitor the fresh levels of chilled beef. Moreover, the utilization of deep learning models (ResNet34, VGG16, and GoogleNet) for chilled beef freshness evaluation achieved an overall accuracy of 98.0 %. Furthermore, t-distributed stochastic neighbour embedding (t-SNE) visualized the feature extraction process and provided explanations to understand the classification process of deep learning. The results demonstrated that applying deep learning techniques in the process of pattern recognition of CSA can help in realizing the rapid, robust, and accurate assessment of chilled beef freshness.

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.

Application progress of nanocellulose in food packaging: A review

With the increasing environmental and ecological problems caused by petroleum-based packaging materials, the focus has gradually shifted to natural resources for the preparation of functional food packaging materials. In addition to biodegradable properties, nanocellulose (NC) mechanical properties, and rich surface chemistry are also fascinating and desired to be one of the most probable green packaging materials. In this review, we firstly introduce the recent progress of novel applications of NC in food packaging, including intelligent packaging, nano(bio)sensors, and nano-paper; secondly, we focus on the modification techniques of NC to summarize the properties (antimicrobial, mechanical, hydrophobic, antioxidant, and so on) that are required for food packaging, to expand the new synthetic methods and application areas. After presenting all the latest advances related to material design and sustainable applications, an overview summarizing the safety of NC is presented to promote a continuous and healthy movement of NC toward the field of truly sustainable packaging.

Ammonia-responsive chitosan/polymethacrylamide double network hydrogels with high-stretchability, fatigue resistance and anti-freezing for real-time chicken breast spoilage monitoring

Hydrogels are a promising option for detecting food spoilage in humid conditions, but current indicators are prone to mechanical flaws, posing a concern for packaging systems that require strong mechanical properties. Herein, a double network hydrogel was prepared by polymerizing methacrylamide in a chitosan system with aluminum chloride and glycerol. The resulting hydrogel demonstrated high stretchability (strain >1500 %), notch insensitivity, excellent fatigue resistance, and exceptional anti-freezing capabilities even at -21 °C. When incorporating bromothymol blue (BB) or methyl red (MR), or mixtures of these dyes into the hydrogels as indicators, they exhibited sensitive colorimetric responses to pH and NH3 levels at different temperatures. Hydrogels immobilizing BB to MR ratios of 1:1 and 1:2 displayed clearer and more sensitive color responses when packed into chicken breast, with a sensitivity level of 1.5 ppm of total volatile basic nitrogen (TVB-N). This color response correlated positively with the accumulation of TVB-N on the packaging during storage at both 25 °C and 4 °C, providing sensitive indications of chicken breast deterioration. Overall, the developed hydrogels and indicators demonstrate enhanced performance characteristics, including excellent mechanical strength and highly NH3-sensitive color responses, making significant contributions to the food spoilage detection and intelligent packaging systems field.

Preparation and application of chlorine dioxide gas slow-release fresh-keeping card based on polylactic acid

Blueberries are highly perishable after harvest, so a simple preservation method is needed to extend the shelf life of blueberries. In this study, sodium chlorite-loaded sepiolite was added to polylactide solution with tartaric acid to create a ClO2 gas slow-release fresh-keeping card. The fresh-keeping card absorbs moisture in the air, which causes tartaric acid to enter the sepiolite and react with sodium chlorite to release ClO2 gas slowly. The study investigated the impact of fresh-keeping cards on the quality attributes of blueberries, including appearance, decay rate, ethylene release rate, respiration rate, hardness, ascorbic acid content, and anthocyanin concentration. Low-field nuclear magnetic technology was used to analyze the water state and distribution of blueberries during storage. The results showed that the ClO2 gas released by the fresh-keeping card can destroy ethylene in the air and kill microorganisms in blueberries, thereby delaying fruit decay.

Strong, tough, high-release, and antibacterial nanocellulose hydrogel for refrigerated chicken preservation

Enormous amounts of food resources are annually wasted because of microbial contamination, highlighting the critical role of effective food packaging in preventing such losses. However, traditional food packaging faces several limitations, such as low mechanical strength, poor fatigue resistance, and low water retention. In this study, we aimed to prepare nanocellulose hydrogels with enhanced stretchability, fatigue resistance, high water retention, and antibacterial properties using soy hull nanocellulose (SHNC), polyvinyl alcohol (PVA), sodium alginate (SA), and tannic acid (TA) as raw materials. These hydrogels were applied in food packaging to extend the shelf life of refrigerated chicken. The structure and properties (e.g., mechanical, antibacterial, and barrier properties) of these hydrogels were characterized using different techniques. Fourier-transform infrared spectroscopy revealed the presence of hydrogen and ester bonds in the hydrogels, whereas scanning electron microscopy revealed the three-dimensional network structure of the hydrogels. Mechanical testing demonstrated that the SHNC/PVA/SA/TA-2 hydrogel exhibited excellent tensile properties (elongation = 160 %), viscoelasticity (storage modulus of 1000 Pa), and mechanical strength (compressive strength = 10 kPa; tensile strength = 0.35 MPa). Moreover, under weak acidic and alkaline conditions, the ester bonds of the hydrogel broke down with an increase in pH, improving its swelling and release properties. The SHNC/PVA/SA/TA-2 hydrogel displayed an equilibrium swelling ratio exceeding 300 %, with a release rate of >80 % for the bioactive substance TA. Notably, antibacterial testing showed that the SHNC/PVA/SA/TA-2 hydrogel effectively deactivated Staphylococcus aureus and Escherichia coli, prolonging the shelf life of refrigerated chicken to 10 d. Therefore, the SHNC/PVA/SA/TA hydrogels can be used in food packaging to extend the shelf life of refrigerated meat products. Their cost-effectiveness and simple preparation make them suitable for various applications in the food industry.

Development of CO2-sensitive antimicrobial bilayer films based on gellan gum and sodium alginate/sodium carboxymethyl cellulose and its application in strawberries

To effectively extend the shelf life of fruits meanwhile facilitating consumers to judge their freshness, in this work, a double-layer multifunctional film combining CO2 sensitivity and antibacterial properties was successfully prepared by adding methyl red (MR), bromothymol blue (BTB) into gellan gum (GG) as the sensing inner layer, and doping tannic acid (TA) into sodium alginate with sodium carboxymethyl cellulose (CMC) as the antimicrobial outer layer, which was applied to the freshness indication of strawberries. Microscopic morphology and spectral analysis demonstrated that the bi-layer films were fabricated successfully. The mechanical characteristics, thermal stability, water vapor resistance, and antibacterial capabilities of the bilayer films improved as TA concentration rose. They exhibited noticeable color changes at pH = 2-10 and different concentrations of CO2. Application of the prepared films to strawberries revealed that the GG-MB@SC-6%TA film performed most favorably under 4 °C storage conditions, not only monitoring strawberry freshness but also retaining high soluble solids and titratable acidity, resulting in a slight decrease in hardness and weight loss. Therefore, taking into account all of the physical-functional characteristics, the GG-MB@6%TA film has a broad application prospect for intelligent food packaging.

A paper-based ratiometric fluorescent sensor for NH3 detection in gaseous phase: Real-time monitoring of chilled chicken freshness

A ratiometric fluorescence sensor platform with easy-to-use and accurate is nanoengineered for NH3 quantitative detection and visual real-time monitoring of chicken freshness using smartphones. The ratiometric fluorescent probe formed by combining the zinc ion complex and carbon dots has a double-emitted fluorescence peak. The fluorescence intensity of the complex changed can be clearly observed with the increase of the concentration of ammonia solution under 365 nm wavelength excitation. In order to detect NH3 concentration in gaseous phase, a portable paper-based sensor was designed. The sensor had a good linear relationship with NH3 concentration ranging from 10.0 to 90.0 μmol/L and the LOD value was 288 nM. This fluorescent paper-based sensor was used to check the freshness of chicken breast refrigerated at 4 °C, revealed observable shifts from blue to green. The fluorescent paper-based sensor can detect NH3 concentration in real time and simplify the monitoring process of meat freshness while ensuring accuracy and stability.

Development of Intelligent Indicators Based on Cellulose and Prunus domestica Extracted Anthocyanins for Monitoring the Freshness of Packaged Chicken

Meat is a widely consumed food globally; however, variations in storage conditions along its supply chain can pose a potential food safety risk for consumers. Addressing this concern, we have developed freshness indicators designed to monitor the condition of packaged chicken. In this study, anthocyanins were infused with cellulose paper measuring 2 × 2 cm, and subsequent analysis focused on examining color changes concerning deteriorating chicken stored at 30°C for 48 h, with varying sample sizes being considered. The rise in total volatile nitrogen (TVB-N) compounds from an initial value of 3.64 ± 0.39 mg/100 g to 28.17 ± 1.46 mg/100 g acted as the stimulus for the color change in the indicator, simultaneously influencing the pH from the initial 7.03 ± 0.16 to 8.12 ± 0.39. The microbial load (aerobic plate count) of the chicken samples was also significantly increased. This collective shift in various parameters strongly suggests the occurrence of spoilage in chicken meat. The pH indicators exhibited a dark pink to red color for fresh chicken. As the chicken meat turned towards spoilage, the indicators changed to a dark blue and then a pale green color. FTIR spectroscopy results confirmed the presence of cellulose and anthocyanins. The FTIR analysis also validated the immobilization of plum anthocyanins within the cellulose paper and assessed their stability after 8 months of storage. Notably, the indicators demonstrated rapid sensitivity, showing a 20.5% response within one minute of ammonia exposure, which further increased to 29.5% after 3 min of exposure. The total color difference (ΔE) steadily rose in all the examined samples and also under various storage conditions. Overall, the indicators developed in this study exhibited a highly pronounced color transition, capable of distinguishing between fresh and spoiled chicken samples depending on the extent of spoilage and the specific day of observation.

Design and characterization of edible chitooligosaccharide/fish skin gelatin nanofiber-based hydrogel with antibacterial and antioxidant characteristics

Antibacterial and active packaging materials have gained significant research attention in response to the growing interest in food packaging. In this investigation, we developed hydrogel packaging materials with antibacterial and antioxidant properties by incorporating chitooligosaccharide (COS) and fish skin gelatin (FSG) nanofiber membranes, which readily absorbed water and exhibited swelling characteristics. The nanofiber membranes were fabricated by electrospinning technology, embedding COS within FSG, and subsequently crosslinked through the Maillard reaction facilitated by the addition of glucose. The behavior of conductivity, viscosity, and surface tension in the spinning solutions was analyzed to understand their variation patterns. Scanning electron microscopy (SEM) results revealed that the crosslinked COS/FSG nanofiber membranes possessed a uniform yet disordered fiber structure, with the diameter of the nanofibers increasing as the COS content increased. Remarkably, when the COS content reached 25 %, the COS/FSG nanofiber membranes (CF-C-25) exhibited a suitable fiber diameter of 437.16 ± 63.20 nm. Furthermore, the thermal crosslinking process involving glucose supplementation enhanced the hydrophobicity of CF-C-25. Upon hydration, the CF-H-25 hydrogel displayed a distinctive porous structure, exhibiting a remarkable swelling rate of 954 %. Notably, the inclusion of COS significantly augmented the antibacterial and antioxidant properties of the hydrogel-based nanofiber membranes. CF-H-25 demonstrated an impressive growth inhibition of 90.56 ± 5.91 % against E. coli, coupled with excellent antioxidant capabilities. In continuation, we performed a comprehensive analysis of the total colony count, pH, TVB-N, and TBA of crucian carp. The CF-H-25 hydrogel proved highly effective in extending the shelf life of crucian carp by 2-4 days, suggesting its potential application as an edible membrane for aquatic product packaging.

Unlocking the potential of cotton stalk as a renewable source of cellulose: A review on advancements and emerging applications

Cotton stalk (CS) is a global agricultural residue, with an annual production of approximately 50 million tons, albeit with limited economic significance. The utilization of cellulose derived from CS has gained significant attention in green nanomaterial technologies. This interest stems from its unique properties, including biocompatibility, low density, minimal thermal expansion, eco-friendliness, renewability, and its potential as an alternative source for chemicals, petroleum, and biofuels. In this review, we delve into various extraction and characterization methods, the physicochemical attributes, recent advancements, and the applications of cellulose extracted from CS. Notably, the steam explosion method has proven to yield the highest cellulose content (82 %) from CS. Moreover, diverse physicochemical properties of cellulose can be obtained through different extraction techniques. Sulfuric acid hydrolysis, for instance, yields nanocrystalline cellulose fibers measuring 10-100 nm in width and 100-850 nm in length. Conversely, the steam explosion method yields cellulose fibers with dimensions of 10.7 μm in width and 1.2 mm in length. CS-derived products, including biochar, aerogel, dye adsorbents, and reinforcement fillers, find applications in various industries, such as environmental remediation and biodegradable packaging. This is primarily due to their ready availability, cost-effectiveness, and sustainable nature.

Preparation of nanocellulose and its applications in wound dressing: A review

Nanocellulose, as a nanoscale polymer material, has garnered significant attention worldwide due to its numerous advantages including excellent biocompatibility, thermal stability, non-toxicity, large specific surface area, and good hydrophilicity. Various methods can be employed for the preparation of nanocellulose. Traditional approaches such as mechanical, chemical, and biological methods possess their own distinct characteristics and limitations. However, with the growing deterioration of our living environment, several green and environmentally friendly preparation techniques have emerged. These novel approaches adopt eco-friendly technologies or employ green reagents to achieve environmental sustainability. Simultaneously, there is a current research focus on optimizing traditional nanocellulose preparation methods while addressing their inherent drawbacks. The combination of mechanical and chemical methods compensates for the limitations associated with using either method alone. Nanocellulose is widely used in wound dressings owing to its exceptional properties, which can accelerate the wound healing process and reduce patient discomfort. In this paper, the principle, advantages and disadvantages of each preparation method of nanocellulose and the research findings in recent years are introduced Moreover, this review provides an overview of the utilization of nanocellulose in wound dressing applications. Finally, the prospective trends in its development alongside corresponding preparation techniques are discussed.

Recent trends in polysaccharide-based biodegradable polymers for smart food packaging industry

Artificial packaging materials, such as plastic, can cause significant environmental problems. Thus, the use of polysaccharide-based biodegradable polymers (cellulose, starch, and alginate) has the potential in the field of environmental sustainability, reprocessing, or protection of the environment. Morphological and structural alterations caused by material degradation have a substantial impact on polymer material characteristics. To avoid degradation during storage, it is critical to evaluate and comprehend the structure, characteristics, and behavior of modern bio-based materials for potential food packaging applications. Hence, this review focused on the various types of polysaccharide-based biodegradable polymers (cellulose, starch, and alginate), their properties, and their commercial potential for food packaging applications. In addition, we overviewed the recent development of polysaccharide-based biodegradable polymer (cellulose, starch, and alginate) packaging for food products. The review concluded that the membrane and chromatographics are widely used in production of cellulose, starch, and alginate-based biodegradable polymers. Also, nanotechnology-based food packaging is widely used to improve the properties of cellulose, starch, and alginate biodegradable polymers and the incorporation of active agents to enhance the shelf life of food products. Overall, the review highlighted the potential of cellulose, starch, and alginate biodegradable polymers in the food packaging industry and the need for potential research and development to improve their properties and commercial viability.

Carboxymethyl chitosan/polyvinyl alcohol double network hydrogels prepared by freeze-thawing and calcium chloride cross-linking for efficient dye adsorption

The discharge of dye wastewater resulting from rapid industrial development has become a serious environmental concern. Therefore, there is a pressing need to develop efficient methods and technologies for the removal of dye pollutants. This study introduced a double network hydrogel, with varying carboxymethyl chitosan (CMCS) contents and polyvinyl alcohol (PVA), employing a combination of freeze- thawing and calcium chloride cross-linking. The investigation focused on the rheological properties of the hydrogels and their removal ability of acidic blue 93 (AB). The results showed that the strength and viscoelastic modulus of composite hydrogels were positively correlated with the CMCS content, and all composite hydrogels exhibited the typical weak strain overshoot behavior. The pore size of the gel initially decreased and then increased, with the densest pores observed at 4 wt% CMCS, showing the optimal removal ability for AB. The adsorption process followed pseudo second-order kinetic model, dominated by external diffusion, and exhibited inhomogeneous multilayer adsorption. This study unveils the potential of CMCS/PVA gels as adsorbents, offering inspirations for the design and development of polyvinyl alcohol-based gels for applications in the food industry.

Recent Studies and Applications of Hydrogel-Based Biosensors in Food Safety

Food safety has increasingly become a human health issue that concerns all countries in the world. Some substances in food that can pose a significant threat to human health include, but are not limited to, pesticides, biotoxins, antibiotics, pathogenic bacteria, food quality indicators, heavy metals, and illegal additives. The traditional methods of food contaminant detection have practical limitations or analytical defects, restricting their on-site application. Hydrogels with the merits of a large surface area, highly porous structure, good shape-adaptability, excellent biocompatibility, and mechanical stability have been widely studied in the field of food safety sensing. The classification, response mechanism, and recent application of hydrogel-based biosensors in food safety are reviewed in this paper. Furthermore, the challenges and future trends of hydrogel biosensors are also discussed.

Organohydrogels with cellulose nanofibers enhanced supramolecular interactions toward high performance self-adhesive sensing pads

Gel materials with tailored functions and tissue-like properties have gained significant interest in emerging applications, including tissue engineering scaffolds, flexible electronics, and soft robotics. In this work, we developed a stretchable, flexible, adhesive, and conductive organohydrogel through physical cross-linking of the poly (N-[tris (hydroxymethyl) methyl] acrylamide-co-acrylamide) (denoted as P(THMA-AM)) network in the presence of cellulose nanofiber (CNF), sodium chloride, and glycerol. The gel matrix is rich in intermolecular interactions, including hydrogen bonding and ionic interactions, which contribute to a highly compact and cohesive structure without the requirement of any chemical crosslinkers. Moreover, the plasticizing effect of glycerol can mitigate the self-entanglement of CNFs, enhancing their mobility and ultimately conferring the organohydrogel with exceptional stretchability and flexibility. The resulting organohydrogel exhibited superior mechanical properties, self-adhesion, and ionic conductivity, making it an excellent candidate for strain-sensing applications, particularly in distinguishing and monitoring human movements.

A Novel Indicator Based on Polyacrylamide Hydrogel and Bromocresol Green for Monitoring the Total Volatile Basic Nitrogen of Fish

An intelligent indicator was developed by immobilizing bromocresol green (BCG) within the polyacrylamide (PAAm) hydrogel matrix to monitor the total volatile basic nitrogen (TVB-N) content of fish. The FTIR analysis indicated that BCG was effectively incorporated into the PAAm through the formation of intermolecular hydrogen bonds. A thermogravimetric analysis (TGA) showed that the PAAm/BCG indicator had a mere 0.0074% acrylamide monomer residue, meanwhile, the addition of BCG improved the thermal stability of the indicator. In vapor tests with various concentrations of trimethylamine, the indicator performed similarly at both 4 °C and 25 °C. The total color difference values (ΔE) exhibited a significant linear response to TVB-N levels ranging from 4.29 to 30.80 mg/100 g at 4 °C (R2 = 0.98). Therefore, the PAAm/BCG indicator demonstrated stable and sensitive color changes based on pH variations and could be employed in smart packaging for real-time assessment of fish freshness.

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.

Banana biomass waste: A prospective nanocellulose source and its potential application in food industry - A review

Bananas are among the most produced and consumed fruit all over the world. However, a vast amount of banana biomass is generated because banana trees bear fruit only once in their lifetime. This massive amount of biomass waste is either disposed of in agricultural fields, combusted, or dumped at plantations, thus posing environmental concerns. Nanocellulose (NC) extraction from this source can be one approach to improve the value of banana biomass. Owing to its superb properties, such as high surface area and aspect ratio, good tensile strength, and high thermal stability, this has facilitated nanocellulose application in the food industry either as a functional ingredient, an additive or in food packaging. In this review, two different applications of banana biomass NC were identified: (i) food packaging and (ii) food stabilizers. Relevant publications were reviewed, focusing on the nanocellulose extraction from several banana biomass applications as food additives, as well as on the safety and regulatory aspects. Ultimately, further research is required to prompt a perspicuous conclusion about banana biomass NC safety, its potential hazards in food applications, as well as its validated standards for future commercialization.

Preparation of Nanopaper for Colorimetric Food Spoilage Indication

In this study, we are reporting the fabrication of a nanocellulose (NFC) paper-based food indicator for chicken breast spoilage detection by both visual color change observation and smartphone image analysis. The indicator consists of a nanocellulose paper (nanopaper) substrate and a pH-responsive dye, bromocresol green (BCG), that adsorbs on the nanopaper. The nanopaper is prepared through vacuum filtration and high-pressure compression. The nanopaper exhibits good optical transparency and strong mechanical strength. The color change from yellow to blue in the nanopaper indicator corresponding to an increase in the solution pH and chicken breast meat storage data were observed and analyzed, respectively. Further, we were able to use color differences determined by the RGB values from smartphone images to analyze the results, which indicates a simple, sensitive, and readily deployable approach toward the development of future smartphone-based food spoilage tests.

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.

High-yield production of rod-like and spherical nanocellulose by controlled enzymatic hydrolysis of mechanically pretreated cellulose

In this study, a simple and scalable mechanical pretreatment was evaluated as means to increase the cellulose accessibility of cellulose fibers, with the aim of improving the efficiency of enzymatic reactions for the production of cellulose nanoparticles (CNs). In addition, the effects of enzyme type (endoglucanase - EG, endoxylanase - EX, and a cellulase preparation - CB), composition ratio (0-200UEG:0-200UEX or EG, EX, and CB alone), and loading (0 U-200 U) were investigated in relation to CN yield, morphology, and properties. The combination of mechanical pretreatment and specific conditions for enzymatic hydrolysis substantially improved CN production yield, reaching up to 83 %. The production of rod-like or spherical nanoparticles and their chemical composition were highly dependent on the type of enzyme, composition ratio, and loading. However, these enzymatic conditions minimally affected the crystallinity index (approximately 80 %) and thermal stability (T_max within 330-355 °C). Collectively, these results demonstrate that mechanical pretreatment followed by enzymatic hydrolysis under specific conditions is a suitable method to produce nanocellulose with a high yield and tunable properties such as purity, rod-like or spherical forms, high thermal stability, and high crystallinity. Therefore, this production route is a promising approach to produce tailored CNs with the potential to offer superior performance in a variety of sophisticated applications, including, but not limited to, wound dressings, drug delivery, thermoplastic composites, 3D (bio)printing, and smart packaging.

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.

Visual Colorimetric Detection of Edible Oil Freshness for Peroxides Based on Nanocellulose

Traditional methods for evaluating the edibility of lipids involve the use of organic reagents and complex operations, which limit their routine use. In this study, nanocellulose was prepared from bamboo, and a colorimetric reading strategy based on nanocellulose composite hydrogels was explored to monitor the freshness of edible oils. The hydrogels acted as carriers for peroxide dyes that changed color according to the freshness of the oil, and color information was digitized using UV-vis and RGB analysis. The sensitivity and accuracy of the hydrogel were verified using H₂O₂, which showed a linear relationship between absorbance and H₂O₂ content in the range of 0-0.5 and 0.5-11 mmol/kg with R² of 0.9769 and 0.9899, respectively, while the chromatic parameter showed an exponential relationship with R² of 0.9626. Surprisingly, the freshness of all seven edible oil samples was correctly identified by the hydrogel, with linear correlation coefficients greater than 0.95 in the UV-vis method and exponential correlation coefficients greater than 0.92 in the RGB method. Additionally, a peroxide value color card was established, with an accuracy rate of 91.67%. This functional hydrogel is expected to be used as a household-type oil freshness indicator to meet the needs of general consumers.

Nanocellulose: An amazing nanomaterial with diverse applications in food science

Recently, nanocellulose has gained growing interests in food science due to its many advantages including its broad resource of raw materials, renewability, interface stability, high surface area, mechanical strength, prebiotic characteristics, surface chemistry versatility and easy modification. Since then, this review summarized the sources, morphology, and structure characteristics of nanocellulose. Meanwhile, the mechanical, chemical, and combined treatment methods for the preparation of nanocellulose with desired properties were elaborated. Furthermore, the application of nanocellulose in Pickering emulsions, reinforced food packaging, functional food ingredient, food-grade hydrogels, and biosensors were emphasized. Finally, the safety, challenges, and future perspectives of nanocellulose were discussed. This work provided key developments and effective benefits of nanocellulose for future research opportunities in food.

Novel color stability and colorimetry-enhanced intelligent CO2 indicators by metal complexation of anthocyanins for monitoring chicken freshness

This study aims to improve the color stability of anthocyanins and develop a CO2-sensitive indicator based on black goji anthocyanin (BGA) extract. Although the BGA extracts showed distinct color changes, such as red-purple-blue, their intrinsic color diminished after 24 h. A metal complexation method was used for the high color stability of BGA. BGA extracts were chelated with various concentrations of Al3+ [0 - 20% (w/w)]. It showed high color stability and strong intensity in a dose-dependent manner. A CO2-sensitive indicator sachet was developed using hydroxypropyl methylcellulose hydrogel, based on 5% (w/w) Al3+-BGA complexes. The indicator was applied to the chicken breast and detected its spoilage after 3 days with its changing color to greyish blue, due to the microbial growth to 7.00 log CFU/g. These results demonstrated the possibility of chelated anthocyanin complexes as indicating dyes and the ability to monitor the food quality changes through noticeable color changes.

Reflections on food security and smart packaging

Estimating the number of COVID-19 cases in 2020 exacerbated the food contamination and food supply issues. These problems make consumers more concerned about food and the need to access accurate information on food quality. One of the main methods for preserving the quality of food commodities for export, storage, and finished products is food packaging itself. In the food industry, food packaging has a significant role in the food supply which acts as a barrier against unwanted substances and preserves the quality of the food. Meanwhile, packaging waste can also harm the environment; namely, it can become waste in waterways or become garbage that accumulates because it is nonrenewable and nonbiodegradable. The problem of contaminated food caused by product packaging is also severe. Therefore, to overcome these challenges of safety, environmental impact, and sustainability, the role of food packaging becomes very important and urgent. In this review, the authors will discuss in more detail about new technologies applied in the food industry related to packaging issues to advance the utilization of Smart Packaging and Active Packaging.

Innovative processes in smart packaging. A systematic review

Smart packaging provides one possible solution that could reduce greenhouse gas emissions. In comparison with traditional packaging, which aims to extend the product's useful life and to facilitate transport and marketing, smart packaging allows increased efficiency, for example by ensuring authenticity and traceability from the product's origin, preventing fraud and theft, and improving security. Consequently, it may help to reduce pollution, food losses, and waste associated with the food supply chain. However, some questions must be answered to fully understand the advantages and limitations of its use. What are the most suitable smart packaging technologies for use in agro-industrial subsectors such as meat, dairy, fruits, and vegetables, bakery, and pastry? What are the opportunities from a perspective of life extension, process optimization, traceability, product quality, and safety? What are the future challenges? An up-to-date, systematic review was conducted of literature relevant to the application of indicator technologies, sensors, and data carriers in smart packaging, to answer these questions. © 2022 Society of Chemical Industry.

Biopolymer Food Packaging Films Incorporated with Essential Oils

Petroleum-based packaging materials are typically nonbiodegradable, which leads to significant adverse environmental and health issues. Therefore, developing novel efficient, biodegradable, and nontoxic food packaging film materials has attracted increasing attention from researchers. Due to significant research and advanced technology, synthetic additives in packaging materials are progressively replaced with natural substances such as essential oils (EOs). EOs demonstrate favorable antioxidant and antibacterial properties, which would be an economical and effective alternative to synthetic additives. This review summarized the possible antioxidant and antimicrobial mechanisms of various EOs. We analyzed the properties and performance of food packaging films based on various biopolymers incorporated with EOs. The progress in intelligent packaging materials has been discussed as a prospect of food packaging materials. Finally, the current challenges regarding the practical application of EOs-containing biopolymer films in food packaging and areas of future research have been summarized.

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.

Engineered nanomaterials-based sensing systems for assessing the freshness of meat and aquatic products: A state-of-the-art review

Meat and aquatic products are susceptible to spoilage during distribution, transportation, and storage, increasing the urgency of freshness evaluation. Engineered nanomaterials (ENMs) typically with the diameter in the range of 1-100 nm exhibit fascinating physicochemical properties. ENMs-based sensing systems have received extensive attention for food freshness assessment due to the advantages of being fast, simple, and sensitive. This review focuses on summarizing the recent application of ENMs-based sensing systems for food freshness detection. First, chemical indicators related to the freshness of meat and aquatic products are described. Then, how to apply the ENMs including noble metal nanomaterials, metal oxide nanomaterials, carbon nanomaterials, and metal-organic frameworks for the construction of different sensing systems were described. Besides, the recent advance in ENMs-based colorimetric, fluorescent, electrochemical, and surface-enhanced Raman spectroscopy sensing systems for assessing the freshness of meat and aquatic products were outlined. Finally, the challenges and future research perspectives for the application of ENMs-based sensing systems were discussed. The ENMs-based sensing systems have been demonstrated as effective tools for freshness evaluation. The sensing performance of ENMs employed in different sensing systems depends on their composition, size, shape, and stability of nanoparticles. For the real application of ENMs in food industries, the risks and regulatory issues associated with nanomaterials need to be further considered. With the continuous development of nanomaterials and sensing devices, the ENMs-based sensors are expected to be applied in-field for rapid detection of the freshness of meat and aquatic products in the future.

Recent advances in cellulose microgels: Preparations and functionalized applications

Microgels are soft, deformable, permeable, and stimuli-responsive microscopic polymeric particles that are now emerging as prospective multifunctional soft materials for delivery systems, interface stabilization, cell cultures and tissue engineering. Cellulose microgels are emerging biopolymeric microgels with unique characteristics such as abound hydroxyl structure, admirable designability, multiscale pore network and excellent biocompatibility. This review summarizes the fabrication strategies for microgel, then highlights the fabrication routes for cellulose microgels, and finally elaborates cellulose microgels' bright application prospects with unique characteristics in the fields of controlled release, interface stabilization, coating, purification, nutrition/drug delivery, and bio-fabrication. The challenges to be addressed for further applications and considerable scope for development in future of cellulose microgels are also discussed.

Mechanically Enhanced Nanocrystalline Cellulose/Reduced Graphene Oxide/Polyethylene Glycol Electrically Conductive Composite Film

Traditional conductive materials do not meet the increasing requirements of electronic products because of such materials' high rigidity, poor flexibility, and slow biodegradation after disposal. Preparing flexible conductive materials with excellent mechanical properties is an active area of research. The key to flexible conductive materials lies in the combination of the polymer matrix and conductive components. This combination can be achieved by making a film of renewable nano-microcrystalline cellulose (NCC) and reduced graphene oxide (rGO) with excellent electrical conductivity-by simple filtration and introducing polyethylene glycol (PEG) to enhance the functionality of the composite film. Graphene imparted conductivity to the composite film, which reached 5.67 S·m^-1. A reinforced NCC/rGO/PEG-4 composite film with a thickness of only 21 μm exhibited a tensile strength of 30.56 MPa, which was 83% higher than that of the sample without PEG (16.71 MPa), and toughness of 727.18 kJ·m^-3, which was about 132% higher than that of the control sample (NCC/rGO, 313.86 kJ·m^-3). This ultra-thin conductive composite film-which can be prepared simply, consists of environmentally sustainable and biodegradable raw materials, and exhibits excellent mechanical properties-has substantial potential for applications in e.g., flexible electronic wearable devices, electrodes, and capacitors.

Antibacterial Capability of MXene (Ti3C2Tx) to Produce PLA Active Contact Surfaces for Food Packaging Applications

The globalization of the market and the increase of the global population that requires a higher demand of food products superimposes a big challenge to ensure food safety. In this sense, a common strategy to extend the shelf life and save life of food products is by avoiding bacterial contamination. For this, the development of antibacterial contact surfaces is an urgent need to fulfil the above-mentioned strategy. In this work, the role of MXene (Ti₃C₂T_x) in providing antibacterial contact surfaces was studied through the creation of composite films from polylactic acid (PLA), as the chosen polymeric matrix. The developed PLA/MXene films maintained the thermal and mechanical properties of PLA and also presented the attractive antibacterial properties of MXene. The composites' behaviour against two representative foodborne bacteria was studied: Listeria mono-cytogenes and Salmonella enterica (representing Gram-positive and Gram-negative bacteria, respectively). The composites prevented bacterial growth, and in the case of Listeria only 0.5 wt.% of MXene was necessary to reach 99.9999% bactericidal activity (six log reductions), while against Salmonella, 5 wt.% was necessary to achieve 99.999% bactericidal activity (five log reductions). Cy-totoxicity tests with fHDF/TER166 cell line showed that none of the obtained materials were cytotoxic. These results make MXene particles promising candidates for their use as additives into a polymeric matrix, useful to fabricate antibacterial contact surfaces that could prove useful for the food packaging industry.

Nanocellulose-Based Nanocomposites for Sustainable Applications: A Review

Nanocellulose has emerged in recent years as one of the most notable green materials available due to its numerous appealing factors, including its non-toxic nature, biodegradability, high aspect ratio, superior mechanical capabilities, remarkable optical properties, anisotropic shape, high mechanical strength, excellent biocompatibility and tailorable surface chemistry. It is proving to be a promising material in a range of applications pertinent to the material engineering to biomedical applications. In this review, recent advances in the preparation, modification, and emerging application of nanocellulose, especially cellulose nanocrystals (CNCs), are described and discussed based on the analysis of the latest investigations. This review presents an overview of general concepts in nanocellulose-based nanocomposites for sustainable applications. Beginning with a brief introduction of cellulose, nanocellulose sources, structural characteristics and the extraction process for those new to the area, we go on to more in-depth content. Following that, the research on techniques used to modify the surface properties of nanocellulose by functionalizing surface hydroxyl groups to impart desirable hydrophilic-hydrophobic balance, as well as their characteristics and functionalization strategies, were explained. The usage of nanocellulose in nanocomposites in versatile fields, as well as novel and foreseen markets of nanocellulose products, are also discussed. Finally, the difficulties, challenges and prospects of materials based on nanocellulose are then discussed in the last section for readers searching for future high-end eco-friendly functional materials.