Understanding physicochemical properties changes from multi-scale structures of starch/CNT nanocomposite films

An effective preserving strategy for strawberries by constructing pectin/starch coatings reinforced with functionalized eggshell fillers

Food waste occurs frequently worldwide, though hunger and malnutrition issues have received global attention. Short-term spoilage of perishable foods causes a significant proportion of food waste. Developing simple, green, and low-cost strategies to preserve the freshness of perishable foods is important to address this issue and improving food safety. By using strawberries as the model perishable fruit, this study reported a pectin/carboxy methyl starch sodium (PC) based coating using epigallocatechin gallate-loaded eggshell powder (ES@EGCG) as the functional fillers. In comparison to PC coating, the PC-ES@EGCG coating displayed much-enhanced performance, such as enhanced mechanical (2 folds) and barrier (water vapor & oxygen) properties. This composite coating reduced the weight loss of strawberries from over 60% to around 30% after 7-day storage. Coated strawberries exhibit better freshness retention, which achieves the purpose of preserving strawberries during storage. This study provided a cost-effective and eco-friendly coating strategy for reducing food waste.

Structure and properties of starch - BaSO4 composite obtained using mechanical activation techniques

The aim of this study is to obtain and characterize starch films structurally modified by in situ precipitation of BaSO4 combined with mechanical activation of casting dispersion in a rotor-stator device. By the rheological method, it was found that the modification causes a decrease in the ability of casting dispersions to structure over time. Composite films with a filler content of 0 %-15 % (w/w) were characterized using optical and SEM microscopy, FT-IR spectroscopy, and tensile and moisture resistance testing data. The maximum increase in strength (by 70 %) and elongation at break (by 870 %) is achieved with a filler content of 5 % and 15 %, respectively. An increase in the filler content to 5 % causes an increase in starch recrystallization rate, but at concentrations above 5 % of BaSO4, it inhibits retrogradation. The films obtained by mechanical activation with optimized parameters were uniformly translucent, had lower water vapor permeability than films made from starch alone, had high flexibility, and did not warp or shrink. The developed high-performance, environmentally friendly method can be recommended for the large-scale production of starch-based composite materials.

Multifunctional Ti3C2Tx MXene-reinforced thermoplastic starch nanocomposites for sustainable packaging solutions

Starch-derived films exhibit significant potential for packaging applications owing to their low cost, biodegradable characteristics, and natural abundance. Nonetheless, there is a demand to enhance their mechanical properties and moisture resistance to broaden their use. In this study, high performing sorbitol-plasticized starch/Ti3C2Tx MXene nanocomposites, reinforced with ultra-low filler contents, were fabricated for the first time in literature. The MXene nanoplatelets were well-dispersed within the starch matrix while there was a tendency for the fillers to align in-plane, as revealed by polarized Raman spectroscopy. The produced nanocomposite films demonstrate remarkable effectiveness in blocking UV light, offering an additional valuable attribute in food packaging. The Young's modulus and tensile strength of starch films containing 0.75 wt% MXene increased from 439.9 and 11.0 MPa to 764.3 and 20.8 MPa, respectively. The introduction of 1 wt% MXene nanoplatelets reduced the water vapour permeability of starch films from 2.78 × 10-7 to 1.80 × 10-7 g/m h Pa due to the creation of highly tortuous paths for water molecules. Micromechanical theories were also implemented to understand further the reinforcing mechanisms in the biobased nanocomposites. The produced starch nanocomposites not only capitalize on the biodegradable and renewable nature of starch but also harness the unique properties of nanomaterials, paving the way for sustainable and high-performance packaging solutions that align with both consumer and environmental demands.

Recent advances in starch-based coatings for the postharvest preservation of fruits and vegetables

Efficient and low-cost postharvest preservation of fruits and vegetables has always been one of the urgent problems to be solved in the food field. Due to the wide sources, good environmental and human safety, and high biodegradability, starch-based coating preservation method has great application prospects in the postharvest preservation of fruits and vegetables. However, starch materials also have the disadvantages of poor mechanical properties and easy water absorption performance, which makes it difficult to fully meet the requirements in practical production. Therefore, starch is often used in combination with other components to form composite materials. This paper began with an introduction to the preservation principles of edible starch-based coatings, including inherent properties and extra functional properties. Besides, the preservation principles of edible coatings and the recent advances in the field of fruit and vegetable preservation were also comprehensively reviewed, focusing on the preparation and application of starch-based coatings. The information will contribute to the further development of starch-based coatings to improve the postharvest preservation effect of fruits and vegetables.

Advances of blend films based on natural food soft matter: Multi-scale structural analysis

The blend films made of food soft matter are of growing interest to the food packaging industries as a pro-environment packaging option. The blend films have become a novel pattern to replace traditional plastics gradually due to their characteristics of biodegradability, sustainability, and environmental friendliness. This review discussed the whole process of the manufacturing of food soft matter blend films from the raw material to the application due to multi-scale structural analysis. There are 3 stages and 12 critical analysis points of the entire process. The raw material, molecular self-assembly, film-forming mechanism and performance test of blend films are investigated. In addition, 11 kinds of blend films with different functional properties by casting are also preliminarily described. The industrialization progress of blend films can be extended or facilitated by analysis of the 12 critical analysis points and classification of the food soft matter blend films which has a great potential in protecting environment by developing sustainable packaging solutions.

Starch/carbon nanofibers bionanocomposites via melt mixing: Effect of dispersion and compatibility on conductivity and mechanical properties

Biodegradable polymers with conductivity and mechanical properties are required in several applications where it is necessary to substitute conductive synthetic plastics due to the high waste produced. In this study, bionanocomposites (BNCs) have been compounded by thermoplastification of rice starch via melt mixing with carbon nanofibers (NPs) and modified NPs (NPs [M]) using plasma of acrylic acid. Spectroscopy analysis, X-ray diffraction, and morphology were studied to elucidate the effect of dispersion and compatibility on the conductivity and mechanical properties. The incorporation of NPs promoted esterification reactions with starch during the melt mixing process, giving rise to changes in its crystal structure. NPs [M] showed better dispersion and compatibility because the plasma prevents reagglomeration and generates a stronger affinity. BNCs showed significative flexibility with remarked % elongation at break from 5.64 % to 248.60 %, and thermal conductivity increased from 0.10 to 0.58 W/m K, with NPs [M] at 5 %. In contrast, the electrical conductivity remained in the same magnitude order (10-4 S/cm). The better compatibility between starch-NPs [M] hinders electronic transport but increases the propagation of phonons to promote thermal conductivity. BNCs fabricated in this study by a dry and scalable process could be of interest in some application areas (intelligent food packing, electronics, textiles, etc.).

Development and characterization of active starch-based films incorporating graphene/polydopamine/Cu2+ nanocomposite fillers

With increasing environmental awareness and food safety concern worldwide, biodegradable active food packaging gained wide attention in recent years. Starch has been regarded as one of the most potential biomaterials to produce biodegradable films. However, relatively poor functional performance of starch-based films severely limits their application as food packaging materials. Carbon-based fillers can be used to enhance the functional attributes of starch-based films, but they are often difficult to incorporate because of their poor matrix dispersibility. In this study, we developed a simple green method to improve the dispersity of graphene in starch-based films by modifying the graphene surfaces using mussel-inspired polydopamine and copper ions. Spectroscopy and morphology analyses showed the surface of graphene was successfully modified. The addition of the nanocomposites positively influenced the microstructure of the starch-based films, as well as impacting their mechanical, barrier, and thermal properties. Additionally, the composite films exhibited antibacterial activity against food borne pathogens, suggesting promising potential of the films acting as active food packaging. Overall, the method developed in this study has the potential for optimizing and endowing extra properties of starch-based films so as to increase their application in biodegradable food packaging.

Structure and properties of flexible starch-based double network composite films induced by dopamine self-polymerization

Starch-based packaging materials are being developed to alleviate environmental pollution and greenhouse gas emissions associated with plastic-based ones. However, the high hydrophilicity and poor mechanical properties of pure-starch films limit their widespread application. In this study, dopamine self-polymerization was used as a strategy to improve the performance of starch-based films. Spectroscopy analysis showed that strong hydrogen bonding occurred between polydopamine (PDA) and starch molecules within the composite films, which significantly altered their internal and surface microstructures. The composite films had a greater water contact angle (> 90°), which indicated that the incorporation of PDA reduced their hydrophilicity. Additionally, the elongation at break of the composite films was 11-fold higher than pure-starch films, indicating that PDA improved film flexibility, while the tensile strength decreased to some extent. The composite films also exhibited excellent UV-shielding performance. These high-performance films may have practical applications in food and other industries as biodegradable packaging materials.

Thermoplastic Starch-Based Composite Reinforced by Conductive Filler Networks: Physical Properties and Electrical Conductivity Changes during Cyclic Deformation

Conductive polymer composites (CPC) from renewable resources exhibit many interesting characteristics due to their biodegradability and conductivity changes under mechanical, thermal, chemical, or electrical stress. This study is focused on investigating the physical properties of electroconductive thermoplastic starch (TPS)–based composites and changes in electroconductive paths during cyclic deformation. TPS–based composites filled with various carbon black (CB) contents were prepared through melt processing. The electrical conductivity and physicochemical properties of TPS–CB composites, including mechanical properties and rheological behavior, were evaluated. With increasing CB content, the tensile strength and Young’s modulus were found to increase substantially. We found a percolation threshold for the CB loading of approximately 5.5 wt% based on the rheology and electrical conductivity. To observe the changing structure of the conductive CB paths during cyclic deformation, both the electrical conductivity and mechanical properties were recorded in parallel using online measurements. Moreover, the instant electrical conductivity measured online during mechanical deformation of the materials was taken as the parameter indirectly describing the structure of the conductive CB network. The electrical conductivity was found to increase during five runs of repeated cyclic mechanical deformations to constant deformation below strain at break, indicating good recovery of conductive paths and their new formation.

Polysaccharides-based bio-nanostructures and their potential food applications

Polysaccharides are omnipresent biomolecules that hold great potential as promising biomaterials for a myriad of applications in various biotechnological and industrial sectors. The presence of diverse functional groups renders them tailorable functionalities for preparing a multitude of novel bio-nanostructures. Further, they are biocompatible and biodegradable, hence, considered as environmentally friendly biopolymers. Application of nanotechnology in food science has shown many advantages in improving food quality and enhancing its shelf life. Recently, considerable efforts have been made to develop polysaccharide-based nanostructures for possible food applications. Therefore, it is of immense importance to explore literature on polysaccharide-based nanostructures delineating their food application potentialities. Herein, we reviewed the developments in polysaccharide-based bio-nanostructures and highlighted their potential applications in food preservation and bioactive "smart" food packaging. We categorized these bio-nanostructures into polysaccharide-based nanoparticles, nanocapsules, nanocomposites, dendrimeric nanostructures, and metallo-polysaccharide hybrids. This review demonstrates that the polysaccharides are emerging biopolymers, gaining much attention as robust biomaterials with excellent tuneable properties.

Prospect of Polysaccharide-Based Materials as Advanced Food Packaging

The use of polysaccharide-based materials presents an eco-friendly technological solution, by reducing dependence on fossil resources while reducing a product's carbon footprint, when compared to conventional plastic packaging materials. This review discusses the potential of polysaccharides as a raw material to produce multifunctional materials for food packaging applications. The covered areas include the recent innovations and properties of the polysaccharide-based materials. Emphasis is given to hemicelluloses, marine polysaccharides, and bacterial exopolysaccharides and their potential application in the latest trends of food packaging materials, including edible coatings, intelligent films, and thermo-insulated aerogel packaging.

Cross-linked starch-based edible coating reinforced by starch nanocrystals and its preservation effect on graded Huangguan pears

Starch-based nanocomposite film/coating made from cross-linked cassava starch reinforced by starch nanocrystals (SNCs) was successfully prepared. The effects of SNCs contents on the color, transparency, roughness, mechanical properties, water vapor permeability, and FTIR spectroscopy of the films were explored. The results showed that the film with 6% SNCs had the best comprehensive performance. Subsequently, graded Huangguan pears were coated with the formulation-optimized coating and stored at 20 °C for 4 weeks. From the physicochemical parameters of pears, it can be found that the grading treatment was detrimental to the preservation of pears, while the coating treatment was significantly effective for extending shelf life. Besides, the pattern of grading before coating was more advantageous for pear preservation. In general, this study firstly applied cross-linked starch-based nanocomposite coating on the preservation of pear, which had practical significance for expanding the use of nanocomposite coating reinforced by SNCs and pear preservation methods.

Electroconductive starch/multi-walled carbon nanotube films plasticized by 1-ethyl-3-methylimidazolium acetate

Starch/multi-walled carbon nanotube (MWCNT) films were prepared by casting using an ionic liquid (1-ethyl-3-methylimidazolium acetate, [emim⁺][Ac^-]) as plasticizer for the first time. The effect of the MWCNT content (0.25-5 wt.%, with respect to the sum of starch and plasticizer mass) on thermal, mechanical and electroconductive behavior of the films was studied. Films containing 0.5 wt.% MWCNT showed increases of 327 % in maximum tensile strength, 2484 % in Young's modulus and 82 % in elongation at break. The significant improvements are explained by the good MWCNT dispersion in the matrix and by the effect of [emim⁺][Ac^-] as an efficient plasticizer, which leads to higher extensibility. The MWCNT/[emim⁺][Ac^-] combination have a synergistic effect on film electrical conductivity, increasing a 130% (3 wt.% MWCNT). These films, easily prepared by a "green" process, have potential applications in the packaging industry but also in the field of lithium batteries, fuel cells and dye-sensitized solar cells.

Effects of Organic Modification of Montmorillonite on the Properties of Hydroxypropyl Di-Starch Phosphate Films Prepared by Extrusion Blowing

The knowledge gained from starch-nanocomposite-film research has not been fully applied commercially because of the lack of appropriate industrial processing techniques for nanofillers and starch films. Three organically modified montmorillonites (OMMTs) were prepared using a semidry kneading method. The effects of the OMMTs on the structures and properties of starch nanocomposite films, prepared by extrusion blowing, were investigated. The X-ray diffraction (XRD) analysis results revealed that the OMMTs with various quaternary ammonium salts possessed differing layer structures and d-space values. The results of the XRD and Fourier-transform infrared spectroscopy (FT-IR) showed that the starch⁻OMMT interaction resulted in a structural change, namely the starch⁻OMMT films possessed a balanced exfoliated and intercalated nanostructure, while the starch⁻MMT film possessed an exfoliated nanostructure with non-intercalated montmorillonite (MMT). The results of the solid-state nuclear magnetic resonance (NMR) analysis suggested that the starch-OMMT nanocomposite possessed comparatively large quantities of single-helix structures and micro-ordered amorphous regions. The starch⁻OMMT films exhibited good tensile strength (TS) (maximum of 6.09 MPa) and water barrier properties (minimum of 3.48 × 10−10 g·m·m−2·s−1·Pa−1). This study indicates that the addition of OMMTs is a promising strategy to improve the properties of starch films.

Tunable d-Limonene Permeability in Starch-Based Nanocomposite Films Reinforced by Cellulose Nanocrystals

In order to control d-limonene permeability, cellulose nanocrystals (CNC) were used to regulate starch-based film multiscale structures. The effect of sphere-like cellulose nanocrystal (CS) and rod-like cellulose nanocrystal (CR) on starch molecular interaction, short-range molecular conformation, crystalline structure, and micro-ordered aggregated region structure were systematically discussed. CNC aspect ratio and content were proved to be independent variables to control d-limonene permeability via film-structure regulation. New hydrogen bonding formation and increased hydroxypropyl starch (HPS) relative crystallinity could be the reason for the lower d-limonene permeability compared with tortuous path model approximation. More hydrogen bonding formation, higher HPS relative crystallinity and larger size of micro-ordered aggregated region in CS0.5 and CR2 could explain the lower d-limonene permeability than CS2 and CR0.5, respectively. This study provided new insight for the control of the flavor release from starch-based films, which favored its application in biodegradable food packaging and flavor encapsulation.