Role of chitin nanocrystals and nanofibers on physical, mechanical and functional properties in thermoplastic starch films

Influence of chitin nanofibers and gallic acid on physical-chemical and biological performances of chitosan-based films

In this work, chitosan films loaded with gallic acid and different content of chitin nanofibers were prepared and subjected to different characterization techniques. The results showed that the inclusion of gallic acid to chitosan films caused moderate decrease in water vapor permeability (by 29 %) and increased tensile strength of films (by 169 %) in comparison to the neat chitosan films. Furthermore, it was found that the addition of chitin nanofibers up to 30 % into chitosan/gallic acid films additionally improved tensile strength (by 474 %) and reduced plasticity of films (by 171 %), when compared to the chitosan/gallic acid films. Increased concentration of chitin nanofibers in films reduced the overall water vapor permeability of films by 51 %. In addition, gallic acid and chitin nanofibers had synergic effect on high chitosan film's antioxidant and antifungal activity toward Botrytis cinerea (both above 95 %). Finally, chitosan/gallic acid/chitin nanofibers films reduced decay incidence of strawberries, increased total soluble solid content, and promoted high production of some polyphenols during cold storage, in comparison to the control chitosan films and uncoated strawberry samples. Hence, these results suggest that chitosan/gallic acid/chitin nanofibers can present eco-sustainable approach for preservation of strawberries, giving them additional nutritional value.

Hybrid Amyloid-Chitin Nanofibrils for Magnetic and Catalytic Aerogels

In the quest for a sustainable and circular economy, it is essential to explore environmentally friendly alternatives to traditional petroleum-based materials. A promising pathway toward this goal lies in the leveraging of biopolymers derived from food waste, such as proteins and polysaccharides, to develop advanced sustainable materials. Here, we design versatile hybrid materials by hybridizing amyloid nanofibrils derived by self-assembly of whey, a dairy byproduct, with chitin nanofibrils exfoliated from the two distinct allomorphs of α-chitin and β-chitin, extracted from seafood waste. Various hydrogels and aerogels were developed via the hybridization and reassembly of these biopolymeric nanobuilding blocks, and they were further magnetized upon biomineralization with iron nanoparticles. The pH-phase diagram highlights the significant role of electrostatic interactions in gel formation, between positively charged amyloid fibrils and negatively charged chitin nanofibrils. Hybrid magnetic aerogels exhibit a ferromagnetic response characterized by a low coercivity (<50 Oe) and a high specific magnetization (>40 emu/g) at all temperatures, making them particularly suitable for superparamagnetic applications. Additionally, these aerogels exhibit a distinct magnetic transition, featuring a higher blocking temperature (200 K) compared to previously reported similar nanoparticles (160 K), indicating enhanced magnetic stability at elevated temperatures. Finally, we demonstrate the practical application of these hybrid magnetic materials as catalysts for carbon monoxide oxidation, showcasing their potential in environmental pollution control and highlighting their versatility as catalyst supports.

Nanochitin for sustainable and advanced manufacturing

Presently, the rapid depletion of resources and drastic climate change highlight the importance of sustainable development. In this case, nanochitin derived from chitin, the second most abundant renewable polymer in the world, possesses numerous advantages, including toughness, easy processability and biodegradability. Furthermore, it exhibits better dispersibility in various solvents and higher reactivity than chitin owing to its increased surface area to volume ratio. Additionally, it is the only natural polysaccharide that contains nitrogen. Therefore, it is valuable to further develop this innovative technology. This review summarizes the recent developments in nanochitin and specifically identifies sustainable strategies for its preparation. Additionally, the different biomass sources that can be exploited for the extraction of nanochitin are highlighted. More importantly, the life cycle assessment of nanochitin preparation is discussed, followed by its applications in advanced manufacturing and perspectives on the valorization of chitin waste.

Flame-retardant phytic acid-decorated thermoplastic starch/halloysite nanotube composite films with enhanced mechanical strength and excellent barrier properties

Thermoplastic starch (TPS), a green and fully biodegradable composite, is considered the most viable option for replacing petroleum-based polymers. However, the poor mechanical properties, high flammability and moisture absorption susceptibility of TPS severely restrict its large-scale applications. Through PA phosphorylation and blending with halloysite nanotubes (HNTs), phytic acid (PA)-phosphorylated HNT/TPS composite films (HNTPSFs) were fabricated with enhanced mechanical strength, excellent flame retardancy, and improved barrier properties. The introduction of HNTs substantially increased the mechanical properties (tensile strength increased 54.3 % and elongation at break decreased 37.0 %) of TPS films and reduced the diffusion of water vapor (decreased 34.1 %). Thermogravimetric analysis studies demonstrated that the HNTPSFs had exceptional thermal stability at their anticipated working temperatures. Furthermore, when the PA content in the composite films increased, the peak heat release rate, total heat release and fire growth index of the HNTPSFs all decreased substantially, demonstrating the improved flame retardancy of HNTPSFs. Hence, the synthesized fully biodegradable TPS composites show enormous potential in the field of renewable biopolymers.

Polysaccharide-based films: from packaging materials to functional food

A wider application of naturally derived polysaccharides is of great interest as materials for food packaging industry. Biocompatibility and biodegradability of polysaccharide-based films and coatings ally with a shift from application of non-biodegradable petrochemical polymers to the more environmentally friendly ones. Due to a range of inherent features in chemical structure and bioactivity, the polysaccharide materials could bring additional functionality to food packaging. The chelating ability of the polysaccharides provides also their application as carriers of additional active components, such as nanoparticles, essential oils and polyphenols. The improved physicochemical, antibacterial and antioxidant properties of the filled films allows to consider the edible polysaccharide-based films as functional food products. This review is aimed at analysis of evolution of polysaccharide-based food packaging materials from inert one starting from cellophane to recent research works on development of multicomponent polysaccharide-based functional food films and coatings.

Optimized high-yield synthesis of chitin nanocrystals from shrimp shell chitin by steam explosion

This study attempted for the first time to prepare chitin nanocrystals (ChNCs) from shrimp shell chitin using steam explosion (SE) method. Response surface methodology (RSM) approach was used to optimize the SE conditions. Optimum SE conditions to acquire a maximum yield of 76.78 % were acid concentration (2.63 N), time (23.70 min), and chitin to acid ratio (1:22). Transmission electron microscopy (TEM) revealed the ChNCs produced by SE had an irregular spherical shape with an average diameter of 55.70 ± 13.12 nm. FTIR spectra showed ChNCs were slightly different than chitin due to a shift in peak positions to higher wavenumber and higher peak intensities. XRD patterns indicated ChNCs were a typical α-chitin structure. Thermal analysis revealed ChNCs were less thermally stable than chitin. Compared to conventional acid hydrolysis, the SE approach described in this study is simple, fast, easy, and requires less acid concentration and acid quantity, making it more scalable and efficient for synthesizing ChNCs. Furthermore, the characteristics of the ChNCs will shed light on the potential industrial uses for the polymer.

Biodegradable nano-reinforced packaging with improved functionality to extend the freshness and longevity of Plums Oemleria cerasiformis

Food packaging reinforced with Zn-doped TiO2 nanoparticles with enhanced prerequisite film-forming and biodegradable traits was prepared to augment fresh food storage. Pure and tailored metal (Zinc, Copper, and Selenium) doped TiO2 nanoparticles were synthesized and analyzed through multiple characterization techniques (optical spectra, XRD patterns (X-Ray Diffraction), Dynamic Light Scattering, and Scanning Electron Microscopy). The synthesized nanoparticles were tested for their Minimum Inhibitory Concentrations, antimicrobial potential against common lethal food pathogens, and cytotoxicity. Compared to Cu- and Se-doped nanoparticles, Zn-doped TiO2 nanoparticles displayed the most potent antimicrobial activity with insignificant cytotoxicity and were incorporated into the food packaging materials. The developed nano-reinforced food packaging efficaciously augmented the freshness of plums (Oemleria cerasiformis) for 16 days (42 ± 2 °C). The physicomechanical characterization of the nano-reinforced packaging establishes its utility in food packaging applications. The developed biodegradable packaging undergoes complete decomposition within 12 days of storage in natural soil.

Green composites based on thermoplastic starch reinforced with micro- and nano-cellulose by melt blending - A review

Starch is a biodegradable biopolymer, a sustainable material that can replace conventional petrochemical-based plastics. However, starch has some limitations, as it must be processed by heating and treated mechanically with a plasticizer to become thermoplastic starch (TPS). Different variables such as mixing speeds, amount, and kind of plasticizers play a vital role in preparing TPS by melting. Despite this, the properties of the TPS are not comparable with those of traditional plastics. To overcome this limitation, microcellulose or nanocellulose is added to TPS by melt mixing, including the extrusion and internal mixing process, which enables large-scale production. This review aims to compile several studies that evaluate the effect of plasticizers, as well as the relevance of incorporating different cellulosic fillers of different dimensions on the properties of TPS obtained by melt mixing. Potential applications of these materials in food packaging, biomedical applications, and other opportunities are also described.

Characterization and qualitative evaluation of cassava starch-chitosan edible food wrap enriched with culinary leaf powders for eco-friendly food packaging applications

Cassava starch-based edible food wraps were prepared by incorporating leaf powder from Indian curry leaf and Malabar bay leaf, reinforced with different (0.2, 0.4, 0.6, 0.8) wt.% of chitosan. Eleven combinations of films were prepared and their sensory acceptability, physical properties, Fourier-transform infrared spectroscopic (FTIR) spectrum, and scanning electron microscopy (SEM) image, were evaluated. The thickness of the films ranged from 0.198  ±  0.12 to 0.372  ±  0.27 mm. Tensile strength was reported to be the highest (40.71  ±  1.21 MPa) in the curry leaf powder incorporated sample. Maximum elongation at break was reported by bay leaf powder incorporated (5.8  ±  1.59%) sample. The Young's modulus values were observed to be increasing along with the concentration of chitosan. Maximum seal strength values were reported by curry leaf powder incorporated film with 0.8% chitosan (2.93  ±  0.22 N/mm). The leaf powder incorporated samples reported a higher flavonoid content compared to the control. The color analysis (L*, a*, b*) of the films was identical to the natural leaf color. The SEM images indicated a rough texture for the leaf powder incorporated films. The FTIR evaluation confirmed the presence of the respective functional groups. The statistical evaluation done by statistical package for social sciences software showed that all the data were significantly different (P ≤ 0.05.). The study demonstrated the potential of incorporation of leaf powder and chitosan to enhance the properties of starch-based edible packaging.

Nano-chitin: Preparation strategies and food biopolymer film reinforcement and applications

Current trends in food packaging systems are toward biodegradable polymer materials, especially the food biopolymer films made from polysaccharides and proteins, but they are limited by mechanical strength and barrier properties. Nano-chitin has great economic value as a highly efficient functional and reinforcing material. The combination of nano-chitin and food biopolymers offers good opportunities to prepare biodegradable packaging films with enhanced physicochemical and functional properties. This review aims to give the latest advances in nano-chitin preparation strategies and its uses in food biopolymer film reinforcement and applications. The first part systematically introduces various preparation methods for nano-chitin, including chitin nanofibers (ChNFs) and chitin nanocrystals (ChNCs). The nano-chitin reinforced biodegradable films based on food biopolymers, such as polysaccharides and proteins, are described in the second part. The last part provides an overview of the current applications of nano-chitin reinforced food biopolymer films in the food industry.

Part A: Biodegradable Bio-Composite Film Reinforced with Cellulose Nanocrystals from Chaetomorpha linum into Thermoplastic Starch Matrices

In recent years, macroalgae and microalgae have played a significant role in the production of organic matter, fiber, and minerals on Earth. They contribute to both technical and medicinal applications as well as being a healthy and nutritious food for humans and animals. The theme of this work concerns the development and exploitation of Chaetomorpha linum (C. linum) biomass, through the elaboration of a new starch-based composite film reinforced by cellulose nanocrystals (CL-CNC) derived from C. linum. The first step involves the chemical extraction of CL-CNC from dry C. linum algae biomass. To achieve this, three types of cyclic treatment were adopted: alkalinization (sodium hydroxide) followed by bleaching (sodium hypochlorite) and acid hydrolysis (hydrochloric acid). We then studied the optimization of the development of bio-composite films based on corn starch (CS) reinforced by CL-CNC. These polymeric films were produced using the solution-casting technique followed by the thermal evaporation process. Structure and interactions were modified by using different amounts of glycerol plasticizers (20% and 50%) and different CS:CNC ratios (7:3 and 8:2). These materials were characterized by UV visible (UV/Vis), Fourier Transform Infrared (FTIR) and Scanning Electron Microscope (SEM) spectroscopy to understand structure-property relationships. The result revealed that the best matrix composition is 7:3 (CS: CL-CNC) with 50% glycerol, which reflects that the reinforcing effect of CL-CNC was greater in bio-composites prepared with a 50% plasticizer, revealing the formation of hydrogen bonds between CL-CNC and CS.

Fortification of puffed biscuits with chitin and crayfish shell: Effect on physicochemical property and starch digestion

Chitin is a polysaccharide and possesses numerous beneficial properties such as nontoxicity, biodegradability and biocompatibility, which draws much attention to its applications in food. Crayfish shell is a source of chitin alongside an antioxidants and a potential source of beneficial dietary fiber. In this study, chitin (CH) and crayfish shell (CS) with different concentrations were used to study their impact on pasting characteristics of flour mixture (wheat flour and glutinous rice flour) and influence on physicochemical and starch digestion property of puffed biscuit. The Rapid Visco-Analyzer results showed that the viscosity of powder mixture was decreased with the ratio of CH and CS increased. CH resulted in lowest peak viscosity and breakdown values of mixed powder. It was indicated that increasing amounts of CH and CS led to significantly reduced moisture content, expansion ratio but raised density of biscuits. CH and CS inhibited starch digestion and promoted a remarkable increase (P < 0.05) of resistant starch (RS) content. The hydrolysis kinetic analysis suggested a decelerating influence of CH on the hydrolysis content with lower values of equilibrium hydrolysis percentage (C∞) while CS on hydrolysis rate with lower kinetic constant (K). The estimated glycemic index (eGI) of the CH (15-20%) samples were below 55. These results are of great significance in delaying starch digestion and provided a better choice in design of fried puffed snacks for special crowd with chronic diseases such as diabetes, cardiovascular disease, and obesity.

Advances in chitin-based nanoparticle use in biodegradable polymers: A review

Chitin-based nanoparticles are polysaccharide materials that can be produced from a waste stream of the seafood industry: crustacean shells. These nanoparticles have received exponentially growing attention, especially in the field of medicine and agriculture owing to their renewable origin, biodegradability, facile modification, and functionality adjustment. Due to their exceptional mechanical strength and high surface area, chitin-based nanoparticles are ideal candidates for reinforcing biodegradable plastics to ultimately replace traditional plastics. This review discusses the preparation methods for chitin-based nanoparticles and their applications. Special focus is on biodegradable plastics for food packaging making use of the features that can be created by the chitin-based nanoparticles.

Nanochitin and Nanochitosan: Chitin Nanostructure Engineering with Multiscale Properties for Biomedical and Environmental Applications

Nanochitin and nanochitosan (with random-copolymer-based multiscale architectures of glucosamine and N-acetylglucosamine units) have recently attracted immense attention for the development of green, sustainable, and advanced functional materials. Nanochitin and nanochitosan are multiscale materials from small oligomers, rod-shaped nanocrystals, longer nanofibers, to hierarchical assemblies of nanofibers. Various physical properties of chitin and chitosan depend on their molecular- and nanostructures; translational research has utilized them for a wide range of applications (biomedical, industrial, environmental, and so on). Instead of reviewing the entire extensive literature on chitin and chitosan, here, recent developments in multiscale-dependent material properties and their applications are highlighted; immune, medical, reinforcing, adhesive, green electrochemical materials, biological scaffolds, and sustainable food packaging are discussed considering the size, shape, and assembly of chitin nanostructures. In summary, new perspectives for the development of sustainable advanced functional materials based on nanochitin and nanochitosan by understanding and engineering their multiscale properties are described.

Chitin and chitin-based biomaterials: A review of advances in processing and food applications

Chitin is the most abundant natural amino polysaccharide, showing various practical applications owing to its functional properties. However, there are barriers in the development due to the difficulty of chitin extraction and purification, regarding its high crystallinity and low solubility. In recent years, some novel technologies such as microbial fermentation, ionic liquid, electrochemical extraction have emerged for the green extraction of chitin from new sources. Furthermore, nanotechnology, dissolution systems and chemical modification were applied to develop a variety of chitin-based biomaterials. Remarkably, chitin was used in delivering active ingredients and developing functional foods for weight loss, lipid reduction, gastrointestinal health, and anti-aging. Moreover, the application of chitin-based materials was expanded into medicine, energy and the environment. This review outlined the emerging extraction methods and processing routes of different chitin sources and advances in applying chitin-based materials. We aimed to provide some direction for the multi-disciplinary production and application of chitin.

Influence of glucan on physicochemical and rheology properties of chitin nanofibers prepared from Shiitake stipes

Procedures for chitin nanofibers extraction from mushroom significantly modify their structure and physicochemical properties, through disintegration and surface oxidation of glucan residue, as well as surface deacetylation of chitin. Here, four kinds of chitin-glucan nanofibers (CGNF) were isolated form Shiitake stipes via different alkali treatment conditions, wherein glucan content ranged from 6.4 % to 46.8 %. Observations with transmission electron microscopy showed that CGNFs possessed average widths with 5.1 ± 1.2 to 7.1 ± 1.5 nm. The glucan showed a negative effect on the crystal index and thermal stability of CGNFs. A strong positive correlation was observed between glucan residues and zeta potential value. The phenomenon about the increase of viscosity, yield stress and elastic modulus upon glucan decrease was discussed. Overall, the residual glucan offers fungi-derived chitin nanomaterials a diversity of material properties and tuning its content is a feasible approach for customize nano chitin fibers used in nutraceutical and food industry.

Chitin, Chitosan, and Nanochitin: Extraction, Synthesis, and Applications

Crustacean shells are a sustainable source of chitin. Extracting chitin from crustacean shells is ongoing research, much of which is devoted to devising a sustainable process that yields high-quality chitin with minimal waste. Chemical and biological methods have been used extensively for this purpose; more recently, methods based on ionic liquids and deep eutectic solvents have been explored. Extracted chitin can be converted into chitosan or nanochitin. Once chitin is obtained and modified into the desired form, it can be used in a wide array of applications, including as a filler material, in adsorbents, and as a component in biomaterials, among others. Describing the extraction of chitin, synthesis of chitosan and nanochitin, and applications of these materials is the aim of this review. The first section of this review summarizes and compares common chitin extraction methods, highlighting the benefits and shortcomings of each, followed by descriptions of methods to convert chitin into chitosan and nanochitin. The second section of this review discusses some of the wide range of applications of chitin and its derivatives.

Chitin Nanocomposite Based on Plasticized Poly(lactic acid)/Poly(3-hydroxybutyrate) (PLA/PHB) Blends as Fully Biodegradable Packaging Materials

Fully bio-based poly(lactic acid) (PLA) and poly(3-hydroxybutyrate) (PHB) blends plasticized with tributyrin (TB), and their nanocomposite based on chitin nanoparticles (ChNPs) was developed using melt mixing followed by a compression molding process. The combination of PHB and ChNPs had an impact on the crystallinity of the plasticized PLA matrix, thus improving its oxygen and carbon dioxide barrier properties as well as displaying a UV light-blocking effect. The addition of 2 wt% of ChNP induced an improvement on the initial thermal degradation temperature and the overall migration behavior of blends, which had been compromised by the presence of TB. All processed materials were fully disintegrated under composting conditions, suggesting their potential application as fully biodegradable packaging materials.

Nanochitin: Chemistry, Structure, Assembly, and Applications

Chitin, a fascinating biopolymer found in living organisms, fulfills current demands of availability, sustainability, biocompatibility, biodegradability, functionality, and renewability. A feature of chitin is its ability to structure into hierarchical assemblies, spanning the nano- and macroscales, imparting toughness and resistance (chemical, biological, among others) to multicomponent materials as well as adding adaptability, tunability, and versatility. Retaining the inherent structural characteristics of chitin and its colloidal features in dispersed media has been central to its use, considering it as a building block for the construction of emerging materials. Top-down chitin designs have been reported and differentiate from the traditional molecular-level, bottom-up synthesis and assembly for material development. Such topics are the focus of this Review, which also covers the origins and biological characteristics of chitin and their influence on the morphological and physical-chemical properties. We discuss recent achievements in the isolation, deconstruction, and fractionation of chitin nanostructures of varying axial aspects (nanofibrils and nanorods) along with methods for their modification and assembly into functional materials. We highlight the role of nanochitin in its native architecture and as a component of materials subjected to multiscale interactions, leading to highly dynamic and functional structures. We introduce the most recent advances in the applications of nanochitin-derived materials and industrialization efforts, following green manufacturing principles. Finally, we offer a critical perspective about the adoption of nanochitin in the context of advanced, sustainable materials.

Chitin Nanocrystal Hydrophobicity Adjustment by Fatty Acid Esterification for Improved Polylactic Acid Nanocomposites

Bioplastics may solve environmental issues related to the current linear plastic economy, but they need improvement to be viable alternatives. To achieve this, we aimed to add chitin nanocrystals (ChNC) to polylactic acid (PLA), which is known to alter material properties while maintaining a fully bio-based character. However, ChNC are not particularly compatible with PLA, and surface modification with fatty acids was used to improve this. We used fatty acids that are different in carbon chain length (C4–C18) and degree of saturation (C18:2). We successfully used Steglich esterification and confirmed covalent attachment of fatty acids to the ChNC with FTIR and solid-state ¹³C NMR. The morphology of the ChNC remained intact after surface modification, as observed by TEM. ChNC modified with C4 and C8 showed higher degrees of substitution compared to fatty acids with a longer aliphatic tail, while particles modified with the longest fatty acid showed the highest hydrophobicity. The addition of ChNC to the PLA matrix resulted in brown color formation that was reduced when using modified particles, leading to higher transparency, most probably as a result of better dispersibility of modified ChNC, as observed by SEM. In general, addition of ChNC provided high UV-protection to the base polymer material, which is an additional feature that can be created through the addition of ChNC, which is not at the expense of the barrier properties, or the mechanical strength.

Facile route to tri-carboxyl chitin nanocrystals from di-aldehyde chitin modified by selective periodate oxidation

Chitin, a kind of polysaccharide mainly obtained from food waste, has emerged as an important biodegradable biopolymer in composite materials. The difficulty of aldehyde modification, which greatly limited the application of chitin nanocrystals, was addressed by applying a facile route of partial deacetylation followed by periodate oxidation in this study. Deacetylation occurred on the surface of both crystalline and amorphous regions, which were significantly degraded in the following periodate oxidation due to the inevitable cleavage of chitin chains, leading to an increase in the crystallinity index of obtained di-aldehyde chitin. The degree of deacetylation and periodate addition had limited improvement in the aldehyde content of di-aldehyde chitin with a maximum value of around 0.42 mmol/g. With further 2,2,6,6-tetramethylpiperidine-1-oxyl-mediated oxidation, the carboxyl content of tri-carboxyl chitin was improved to 1.58 mmol/g, which played a critical role in the dispersion efficiency and morphology of chitin nanocrystals. The obtained rod-like chitin nanocrystals with a ζ-potential value of -42 mV and an average size of 97 nm have potential application in dye-adsorption and emulsion stabilizers.

A Comprehensive Review on the Emerging Roles of Nanofillers and Plasticizers towards Sustainable Starch-Based Bioplastic Fabrication

Petroleum-based plastics are associated with environmental pollution problems owing to their non-biodegradable and toxic properties. In this context, renewable and biodegradable bioplastics possess great potential to replace petroleum-based plastics in mitigating these environmental issues. Fabrication of bioplastic films involves a delicate mixture of the film-forming agent, plasticizer and suitable solvent. The role of the plasticizer is to improve film flexibility, whereas the filler serves as a reinforcement medium. In recent years, much research attention has been shifted toward devising diverse methods for enhancing the performance of bioplastics, particularly in the utilization of environmentally benign nanoparticles to displace the conventional hazardous chemicals. Along this line, this paper presents the emergence of nanofillers and plasticizers utilized in bioplastic fabrication with a focus on starch-based bioplastics. This review paper not only highlights the influencing factors that affect the optical, mechanical and barrier properties of bioplastics, but also revolves around the proposed mechanism of starch-based bioplastic formation, which has rarely been reviewed in the current literature. To complete the review, prospects and challenges in bioplastic fabrication are also highlighted in order to align with the concept of the circular bioplastic economy and the United Nations’ Sustainable Development Goals.

Preparation, Characterization and Gelation of a Fungal Nano Chitin Derived from Hericium erinaceus Residue

Nano chitin is a promising biocompatible material with wide applications. In this work, a fungal-derived nano chitin was prepared from Hericium erinaceus residue via mineral/protein purification and subsequent TEMPO-mediated oxidation. The structure, dispersity, and gelation ability of the prepared fungal nano chitin were studied. The results showed that the average length and width of the prepared fungal nano chitin were 336.6 nm and 6.4 nm, respectively, and the aspect ratio exceeded 50:1. The nano chitin retained the basic structure of chitin, while the crystallization index was improved. In addition, the dispersity of the nano chitin in aqueous media was evaluated by the effective diameter, and the polydispersion index was mainly affected by pH and ionic strength. Under acetic acid “gas phase coagulation”, the prepared nano chitin dispersions with mass concentrations of 0.2, 0.4, 0.6, and 0.8% were converted into gels by enhanced hydrogen bond crosslinking between nano chitins.

Chitin Nanocrystals: Environmentally Friendly Materials for the Development of Bioactive Films

Biobased nanomaterials have gained growing interest in recent years for the sustainable development of composite films and coatings, providing new opportunities and high-performance products. In particular, chitin and cellulose nanocrystals offer an attractive combination of properties, including a rod shape, dispersibility, outstanding surface properties, and mechanical and barrier properties, which make these nanomaterials excellent candidates for sustainable reinforcing materials. Until now, most of the research has been focused on cellulose nanomaterials; however, in the last few years, chitin nanocrystals (ChNCs) have gained more interest, especially for biomedical applications. Due to their biological properties, such as high biocompatibility, biodegradability, and antibacterial and antioxidant properties, as well as their superior adhesive properties and promotion of cell proliferation, chitin nanocrystals have emerged as valuable components of composite biomaterials and bioactive materials. This review attempts to provide an overview of the use of chitin nanocrystals for the development of bioactive composite films in biomedical and packaging systems.

Crystalline polysaccharides: A review

The biodegradability and mechanical properties of polysaccharides are dependent on their architecture (linear or branched) as well as their crystallinity (size of crystals and crystallinity percent). The amount of crystalline zones in the polysaccharide significantly governs their ultimate properties and applications (from packaging to biomedicine). Although synthesis, characterization, and properties of polysaccharides have been the subject of several review papers, the effects of crystallization kinetics and crystalline domains on the properties and application have not been comprehensively addressed. This review places focus on different aspects of crystallization of polysaccharides as well as applications of crystalline polysaccharides. Crystallization of cellulose, chitin, chitosan, and starch, as the main members of this family, were discussed. Then, application of the aforementioned crystalline polysaccharides and nano-polysaccharides as well as their physical and chemical interactions were overviewed. This review attempts to provide a complete picture of crystallization-property relationship in polysaccharides.

Bioactive Pectin-Murta (Ugni molinae T.) Seed Extract Films Reinforced with Chitin Fibers

This study investigated the biocomposite pectin films enriched with murta (Ugni molinae T.) seed polyphenolic extract and reinforced by chitin nanofiber. The structural, morphological, mechanical, barrier, colorimetric, and antioxidant activity of films were evaluated. The obtained data clearly demonstrated that the addition of murta seed extract and the high load of chitin nanofibers (50%) provided more cohesive and dense morphology of films and improved the mechanical resistance and water vapor barrier in comparison to the control pectin film. The antioxidant activity ranged between 71% and 86%, depending on the film formulation and concentration of chitin nanofibers. The presented results highlight the potential use of chitin nanofibers and murta seed extract in the pectin matrix to be applied in functional food coatings and packaging, as a sustainable solution.

Eco-friendly isolation and characterization of nanochitin from different origins by microwave irradiation: Optimization using response surface methodology

The extraction of nanochitin from marine waste has attracted great industrial interest due to its unique properties, namely biodegradability, biocompatibility and as a functional reinforcing agent. Conventional acid hydrolysis isolation of nanochitin requires high temperatures and acid concentration, time and energy. Herein, for the first time, microwave irradiation method was used as an eco-friendly approach to isolate nanochitin from different sources. The isolation conditions were optimized through an experimental Box-Behnken design using surface response methodology. The data showed optimal conditions of 1 M HCl, 10.00 min and 124.75 W to obtain lobster nanocrystals; 1 M HCl, 14.34 min and 50.21 W to obtain shrimp nanocrystals; and 1 M HCl, 29.08 min and 54.08 W to obtain squid pen nanofibres, reducing time and HCl concentration. The obtained isolation yields where of 85.30, 79.92 and 80.59 % for lobster, shrimp and squid, respectively. The morphology of the nanochitins was dependent of the chitin origin, and the lengths of the nanochitins were of 314.74, 386.12 and > 900 nm for lobster, shrimp and squid pen, respectively. The thermal stability of the ensuing nanochitins was maintained after treatment. The results showed that nanochitin could be obtained by using an eco-friendly approach like microwave irradiation.

Valorization of food waste to produce intelligent nanofibrous β-chitin films

The efficient use of waste from food processing industry is one of the innovative approaches within sustainable development, because it can be transferred into added value products, which could improve economic, energetic and environmental sectors. In this context, the squid pen waste from seafood industry was used as raw material to obtain nanofibrous β-chitin films. In order to extend functionality of obtained films, elderberry extract obtained from biomass was added at different concentrations. The tensile strength of chitin-elderberry extract films was improved by 52%, elongation at break by 153% and water vapor barrier by 65%. The obtained material showed distinct color change when subjected to acidic or basic solutions. It was proven by CIELab color analysis that all color changes could be easily perceived visually. In addition, the obtained nanofibrous film was successfully used to monitor the freshness of Hake fish. Namely, when the film was introduced in a package that contained fresh fish, its color was efficiently changed within the time during the storage at 4 °C. The obtained results demonstrated that food processing waste could be efficiently valorized, and could give sustainable food package design as a spoilage indicator of high protein food.

Thermoplastic bio-nanocomposites: From measurement of fundamental properties to practical application

Although the discovery of plastic has revolutionized materials used in many industries and by consumers, their non-biodegradable nature has led to one of the greatest problems of our times: plastic waste in the environment. Bioplastics which are biobased and biodegradable, have been suggested as alternatives for their fossil based counterparts, but their properties often do not meet the requirements that standard plastics would, and are in clear need of improvement. One way to do so is by the addition of nanoparticles which, when homogeneously dispersed, have been reported to result in great improvements. However, in practice, homogenous distribution of nanoparticles is not that trivial due to their tendency to aggregate, also after addition to the polymer matrix. Although theoretical frameworks to prevent this process are available, we feel that the options explored in practice are often rather trial and error in nature. For that reason, we review the theories available, aiming to facilitate the design of the nanocomposites for a sustainable future. We first discuss thermodynamic frameworks which revolve around nanoparticle aggregation. To minimize nanoparticle aggregation, the nanoparticle and polymer can be selected in such a way that they have similar polar and dispersive surface energies. The second part is dedicated to nanocomposite processing, where kinetic effects act on the nanocomposite material therewith influencing its final morphology, although it is good to point out that other factors such as reaggregation also affect the final nanocomposite morphology. The third section is dedicated to how nanoparticles affect the polymer matrix to which they are added. We describe how interactions at an atomic scale, result in the formation of an interphasial region which ultimately leads to changed bulk material properties. From these three sections, we conclude that three parameters are often overlooked when designing nanocomposites, namely the surface energies of the nanoparticles and polymers, the aggregation bond energy or strength, and the interphase region. Therefore, in the fourth section we provide an overview of techniques to identify these three parameters. We finish with a summery and outlook for the design of bio nanocomposites, where we bring all insights from the previous four sections together.

Preparation and characterization of cross-linked starch nanocrystals and self-reinforced starch-based nanocomposite films

In this study, starch-based nanocomposite films reinforced by cross-linked starch nanocrystals (CSNCs) were successfully prepared. CSNCs were obtained by cross-linking reaction between starch nanocrystals (SNCs) and sodium hexametaphosphate (SHMP). Through the characterization and comparison of SNCs and CSNCs in microscopic morphology, degree of substitution, swelling degree, XRD spectrum, and FTIR spectrum, the successful progress of the cross-linking reaction was confirmed. Besides, the effects of adding CSNCs on physiochemical properties of the nanocomposite films including mechanical properties, water vapor permeability, and contact angle were studied. The results confirmed that CSNCs had good enhancement effects on the physicochemical properties of starch-based films due to the self-reinforcing effect, and when the CSNCs content reached 10%, the nanocomposite film had the best overall performance. We further evaluated the cytotoxicity of the nanocomposite. Taken together, it is believed that the reported self-reinforced starch-based films are very promising for food packaging and preservation.

Chitin nanocrystals based complex fluids: A green nanotechnology

Chitin biopolymer has received significant attention recently by many industries as a green technology. Nanotechnology has been used to make chitin nanocrystals (ChiNCs) that are rod-shaped natural nanomaterials with nanoscale size. Owing to the unique features such as biodegradability, biocompatibility, renewability, rod-shape, and excellent surface and interfacial, physiochemical, and thermo-mechanical properties; ChiNCs have been green and attractive products with wide applications specifically in medical and pharmaceutical, food and packaging, cosmetic, electrical, and electronic, and also in the oil and gas industry. This review aims to give a comprehensive and applied insight into ChiNCs technology. It starts with reviewing different sources of chitin and their extraction methods followed by the characterization of ChiNCs. Furthermore, a detailed investigation into various complex fluids (dispersions, emulsions, foams, and gels) stabilized by ChiNCs and their characterisation have been thoroughly deliberated. Finally, the current status including ground-breaking applications, untapped investigations, and future prospective have been presented.

A review on native well-preserved chitin nanofibrils for materials of high mechanical performance

Novel chitin nanofibrils (ChNF) demonstrate excellent mechanical properties due to a long and extended polymer conformation. The current study highlights the importance of preserving ChNFs for stronger nanomaterials. Various chitin sources - crab, lobster, shrimp, squid pen, mushrooms, and insects have been reviewed. We have discussed preparation protocols and the physical properties of ChNF and presented the mechanical performance of nanomaterials. ChNF close to the native state uses fewer chemicals for treatment and shows a higher molar mass, degree of acetylation, crystallinity index, micrometer length, and a smaller diameter (3 nm), making them cheap, eco-friendly, and competitive to cellulose or synthetic fibrils. A highly acetylated or partially deacetylated ChNF forms a stable colloidal suspension, and it is possible to prepare from it strong films, hydrogels, aerogels, foams, polymer matrix nanocomposites, and microfibers. Moreover, it is possible to regenerate, functionalize, or cross-link the ChNFs to improve nanomaterials' mechanical performance. The preparation protocols remain the key to these achievements. However, the chemical techniques are not friendly ecologically and may hydrolytically degrade the chitin. The biological processes using enzymes or microorganisms are much better but still inefficient. Besides, the processing time limits the rapid preparation of the fibrils in the long-term perspective.

Chemistry, Structures, and Advanced Applications of Nanocomposites from Biorenewable Resources

Researchers have recently focused on the advancement of new materials from biorenewable and sustainable sources because of great concerns about the environment, waste accumulation and destruction, and the inevitable depletion of fossil resources. Biorenewable materials have been extensively used as a matrix or reinforcement in many applications. In the development of innovative methods and materials, composites offer important advantages because of their excellent properties such as ease of fabrication, higher mechanical properties, high thermal stability, and many more. Especially, nanocomposites (obtained by using biorenewable sources) have significant advantages when compared to conventional composites. Nanocomposites have been utilized in many applications including food, biomedical, electroanalysis, energy storage, wastewater treatment, automotive, etc. This comprehensive review provides chemistry, structures, advanced applications, and recent developments about nanocomposites obtained from biorenewable sources.

Maria H, Gopi S, Volova T, C. M. Fernandes S, Thomas S. Extraction of Nanochitin from Marine Resources and Fabrication of Polymer Nanocomposites: Recent Advances

Industrial sea food residues, mainly crab and shrimp shells, are considered to be the most promising and abundant source of chitin. In-depth understanding of the biological properties of chitin and scientific advancements in the field of nanotechnology have enabled the development of high-performance chitin nanomaterials. Nanoscale chitin is of great economic value as an efficient functional and reinforcement material for a wide range of applications ranging from water purification to tissue engineering. The use of polymers and nanochitin to produce (bio) nanocomposites offers a good opportunity to prepare bioplastic materials with enhanced functional and structural properties. Most processes for nanochitin isolation rely on the use of chemical, physical or mechanical methods. Chitin-based nanocomposites are fabricated by various methods, involving electrospinning, freeze drying, etc. This review discusses the progress and new developments in the isolation and physico-chemical characterization of chitin; it also highlights the processing of nanochitin in various composite and functional materials.

Preparation and Properties of Corn Starch/Chitin Composite Films Cross-Linked by Maleic Anhydride

To improve the functional properties of starch-based films, chitin (CH) was prepared from shrimp shell powder and incorporated into corn starch (CS) matrix. Before blending, maleic anhydride (MA) was introduced as a cross-linker. Composite CS/MA-CH films were obtained by casting-evaporation approach. Mechanical property estimation showed that addition of 0–7 wt % MA-CH improved the tensile strength of starch films from 3.89 MPa to 9.32 MPa. Elongation at break of the films decreased with the addition of MA-CH, but the decrease was obviously reduced than previous studies. Morphology analysis revealed that MA-CH homogeneously dispersed in starch matrix and no cracks were found in the CS/MA-CH films. Incorporation of MA-CH decreased the water vapor permeability of starch films. The water uptake of the films was reduced when the dosage of MA-CH was below 5 wt %. Water contact angles of the starch films increased from 22° to 86° with 9 wt % MA-CH incorporation. Besides, the composite films showed better inhibition effect against Escherichia coli and Staphylococcus aureus than pure starch films.

The effect of plasticizers on thermoplastic starch films developed from the indigenous Ethiopian tuber crop Anchote (Coccinia abyssinica) starch

Anchote (Coccinia abyssinica) starch films were prepared by a solution casting method with glycerol, 1-ethyl-3-methylimidazolium acetate, sorbitol or triethylene glycol as plasticizers. The effect of these plasticizers and their concentration on film microstructure, thermal, and mechanical properties was investigated. Scanning electron microscopy revealed that regardless of plasticizer type, films possessing higher plasticizer content had more homogeneous morphologies than those with lower plasticizer content. The FTIR spectra of films plasticized with 1-ethyl-3-methylimidazolium acetate had higher intensity peaks at 3150, 1400 and 1000 cm-1 when compared to other film peaks. These data show that 1-ethyl-3-methylimidazolium acetate plasticized films have decreased molecular order which results in less hydrogen bonding. For this reason, films developed from 1-ethyl-3-methylimidazolium acetate were more flexible than the others. The effect of plasticizers on the thermal properties of the anchote starch films was investigated using thermogravimetric analysis (TGA). Films made from 30% (w/w) plasticizer concentration exhibited higher thermal stability for all types of plasticizer. Mechanical testing showed that sorbitol films had the highest tensile strength, approximately 2 times that of the triethylene glycol plasticized film and 3 times that of the film made from 1-ethyl-3-methylimidazolium acetate.

Effect of Oxidized Wood Pulp Fibers on the Performance of the Thermoplastic Corn Starch Composites

In this study, oxidized wood pulp fiber (OWPF) was prepared by oxidizing wood pulp fiber (WPF) with NaIO4, and OWPFs with different oxidation degrees were obtained and characterized by light microscope, XRD, and TG. Then, OWPFs with different oxidation degrees were incorporated into thermoplastic starch (TPS) to prepare OWPF/TPS composites. The cross-section morphology, water resistance, and physical and mechanical properties of the composites were investigated. SEM showed good dispersion of OWPF in the continuous TPS phase. The tensile strength of OWPF/TPS reached a maximum value of 5.02 MPa when the oxidation degree of OWPF was 0.5. Elongation at break of OWPF/TPS composites increased with the increasing oxidation degree of OWPF. Meanwhile, as a result of cross-linking, the water contact angle was also improved with the increased oxidation degree of OWPF. The study provided a new way to prepare a degradable TPS composite with satisfying properties to be used for packaging and catering.