Selective localization of cellulose nanocrystals in the biodegradable poly(vinyl alcohol)/poly(ε-caprolactone) blend composites prepared by Pickering emulsions

Multi-strategy dynamic cross-linking to prepare EGCG-loaded multifunctional Pickering emulsion/α-cyclodextrin/konjac glucomannan composite films for ultra-durable preservation of perishable fruits

Developing multifunctional films with antibacterial, antioxidant, and sustained-release properties is a robust strategy for preventing contamination of perishable fruits by foodborne microorganisms. This study engineered a sustained-release biodegradable antibacterial film loaded with EGCG (Pickering emulsion (PE)/α-Cyclodextrin (α-CD)/Konjac glucomannan (KGM)) through multi-strategy cross-linking for fruit preservation. EGCG is stabilized using PE and incorporated into the α-CD/KGM inclusion compound; the unique structure of α-CD enhances EGCG encapsulation, while KGM provides the film toughness and surface adhesion. The composite film's physicochemical properties, antioxidant, bacteriostatic and biodegradability were studied. Results showed that Pickering emulsions with 3 % oil phase exhibited excellent stability. Moreover, α-CD introduction increased the loading and sustained release of EGCG from the film, and its concentration significantly affected the light transmission, thermal stability, mechanical strength, mechanical characteristics and antioxidant capacity of the composite membrane. Antioxidant and antimicrobial activities of the composite film increased significantly with increasing α-CD concentration. Application of the film to tomatoes and strawberries effectively inhibited Escherichia coli and Staphylococcus aureus growth, prolonging the shelf-life of the fruits. Notably, the composite film exhibits superior biodegradability in soil. This EGCG-loaded PE/α-CD/KGM composite film is anticipated to be a multifunctional antimicrobial preservation material with sustained-release properties and biodegradable for perishable food applications.

Chitin nanocrystals-stabilized emulsion as template for fabricating injectable suspension containing polylactide hollow microspheres

One of the promising applications of rod-like chitin nanocrystals (ChNCs) is the use as particle emulsifier to develop Pickering emulsions. We reported a ChNC-stabilized oil-in-water emulsion system, and developed a Pickering emulsion-templated method to prepare polylactide (PLA) hollow microspheres here. The results showed that both non-modified ChNCs and acetylated ChNCs could well emulsify the dichloromethane (DCM) solution of PLA-in-aqueous mannitol solution systems, forming very stable emulsions. At the same oil-to-water ratios and ChNC loadings, the emulsion stability was improved with increasing acetylation levels of ChNCs, accompanied by reduced size of droplets. Through the solvent evaporation, the PLA hollow microspheres were templated successfully, and the surface structure was also strongly dependent on the acetylation level of ChNCs. At a low level of acetylation, the single-hole or multi-hole surface structure formed, which was attributed to the out-diffusion of DCM caused by the solvent extraction and evaporation. These surface defects decreased with increased acetylation levels of ChNCs. Moreover, the aqueous suspension with as-obtained PLA microspheres revealed shear-thinning property and good biocompatibility, thereby had promising application as injectable fillers. This work can provide useful information around tuning surface structures of the Pickering emulsion-templated polymer hollow microspheres by regulating acetylation level of ChNCs.

Self-Healing Composite Coating Fabricated with a Cystamine Cross-Linked Cellulose Nanocrystal-Stabilized Pickering Emulsion

A gelled Pickering emulsion system was fabricated by first stabilizing linseed oil droplets in water with dialdehyde cellulose nanocrystals (DACNCs) and then cross-linking with cystamine. Cross-linking of the DACNCs was shown to occur by a reaction between the amine groups on cystamine and the aldehyde groups on the CNCs, causing gelation of the nanocellulose suspension. Fourier transform infrared spectroscopy and X-ray photoelectron spectroscopy were used to characterize the cystamine-cross-linked CNCs (cysCNCs), demonstrating their presence. Transmission electron microscopy images evidenced that cross-linking between cysCNCs took place. This cross-linking was utilized in a linseed oil-in-water Pickering emulsion system, creating a novel gelled Pickering emulsion system. The rheological properties of both DACNC suspensions and nanocellulose-stabilized Pickering emulsions were monitored during the cross-linking reaction. Dynamic light scattering and confocal laser scanning microscopy (CLSM) of the Pickering emulsion before gelling imaged CNC-stabilized oil droplets along with isolated CNC rods and CNC clusters, which had not been adsorbed to the oil droplet surfaces. Atomic force microscopy imaging of the air-dried gelled Pickering emulsion also demonstrated the presence of free CNCs alongside the oil droplets and the cross-linked CNC network directly at the oil-water interface on the oil droplet surfaces. Finally, these gelled Pickering emulsions were mixed with poly(vinyl alcohol) solutions and fabricated into self-healing composite coating systems. These self-healing composite coatings were then scratched and viewed under both an optical microscope and a scanning electron microscope before and after self-healing. The linseed oil was demonstrated to leak into the scratches, healing the gap automatically and giving a practical approach for a variety of potential applications.

Incorporation of fucoxanthin into 3D printed Pickering emulsion gels stabilized by salmon by-product protein/pectin complexes

The remarkable performance of fucoxanthin (FX) in antioxidant and weight loss applications has generated considerable interest. However, the application of fucoxanthin in the food and pharmaceutical industries is limited due to its highly unsaturated structure. This research aimed to investigate the synergistic mechanism of a unique Pickering emulsion gel stabilized by salmon byproduct protein (SP)-pectin (PE) aggregates and evaluate its ability to enhance the stability and bioavailability of FX. Various analytical techniques, including fluorescence spectroscopy, contact angle testing, turbidity analysis, and cryo-field scanning electron microscopy, were used to demonstrate that electrostatic and hydrophobic interactions between SP and PE contribute to the exceptional stability and wettability of the Pickering emulsion gels. Rheological analysis revealed that increasing the concentration of SP-PEs resulted in shear-thinning behavior, excellent thixotropic recovery performance, higher viscoelasticity, and good thermal stability of the Pickering emulsion gels stabilized by SP-PEs(SEGs). Furthermore, encapsulation of FX in the gels showed protected release under simulated oral and gastric conditions, with the subsequent controlled release in the intestine. Compared to free FX and the control group without PE (SEG-0), SEG-4 exhibited a 1.92-fold and 1.37-fold increase in the total bioavailable fraction of FX, respectively. Notably, during the study, it was observed that SEGs have the potential to serve as cake decoration for 3D printing to replace traditional cream under lower oil phase conditions (50%). These findings suggest that SP-PEs-stabilized Pickering emulsion gels hold promise as carriers for delivering bioactive compounds, offering the potential for various innovative food applications.

Effect of surface acetylation of chitin nanocrystals on the preparation and viscoelasticity of sunflower seed oil-in-water Pickering emulsions

Acetylated chitin nanocrystals (ChNCs) were used as stabilizer in this work to prepare sunflower seed oil-in-water emulsions for the morphological and rheological studies. The results revealed that the acetylation with moderate degree of substitution (0.38) reduced hydrophilicity and increased surface charge level of rod-like ChNCs, and as a result, significantly improved the emulsifying ability of ChNCs. At the same oil/water ratio and particle loading, the emulsions stabilized with the acetylated ChNCs had far smaller droplet size (∼3 μm) as compared to the emulsions stabilized with the pristine ChNCs (5-7 μm). The increased droplets numbers and improved surface coating level resulted in the enhanced viscous resistance and yield stress level, which improved the physical stability of the acetylated ChNC-stabilized emulsions as a result. In addition, the droplet clusters easily formed in this system, contributing to weak strain overshoot and decreased large-deformation sensitivity during dynamic shear flow. Therefore, the acetylated ChNC-stabilized system showed enhanced transient stress overshoot during startup flow and weakened thixotropy during cyclic ramp shear flow as compared to the pristine ChNC-stabilized system. The relationships between surface acetylation of ChNCs and flow behavior of emulsions were then established, which provide valuable information on the modulation of the ChNC-stabilized Pickering emulsions.

Multi-functional nanocellulose based nanocomposites for biodegradable food packaging: Hybridization, fabrication, key properties and application

Nowadays, non-degradable plastic packaging materials have caused serious environmental pollution, posing a threat to human health and development. Renewable eco-friendly nanocellulose hybrid (NCs-hybrid) composites as an ideal alternative to petroleum-based plastic food packaging have been extensively reported in recent years. NCs-hybrids include metal, metal oxides, organic frameworks (MOFs), plants, and active compounds. However, no review systematically summarizes the preparation, processing, and multi-functional applications of NCs-hybrid composites. In this review, the design and hybridization of various NCs-hybrids, the processing of multi-scale nanocomposites, and their key properties in food packaging applications were systematically explored for the first time. Moreover, the synergistic effects of various NCs-hybrids on several properties of composites, including mechanical, thermal, UV shielding, waterproofing, barrier, antimicrobial, antioxidant, biodegradation and sensing were reviewed in detailed. Then, the problems and advances in research on renewable NCs-hybrid composites are suggested for biodegradable food packaging applications. Finally, a future packaging material is proposed by using NCs-hybrids as nanofillers and endowing them with various properties, which are denoted as "PACKAGE" and characterized by "Property, Application, Cellulose, Keen, Antipollution, Green, Easy."

Improvement of the emulsifying properties of mixed emulsifiers by optimizing ultrasonic-assisted processing

Optimizing ultrasound (ULD)-assisted flavonoid modification is an important component of enhancing its application potential. In this work, diverse flavonoids, such as quercetin (Que), apigenin (Api), and morin (Mor), were used to modify protein in myofibrillar protein (MP)/cellulose nanocrystal (CN) complexes using ULD-assisted method. Compared with the MP/CNs group, the triiodide contents of MP-Que/CNs, MP-Api/CNs, and MP-Mor/CNs increased by 1175.84%, 479.05%, and 2281.50% respectively. The findings revealed that the actual intensity of ULD was drastically reduced by the molecular weight decrease of these flavonoids. For olive oil emulsions prepared with mixed emulsifiers, the low interfacial diffusion rates (0.03 mN·m·s-1/2) and weak emulsifying activity (8.33 m2/g) of the MP/CN complexes were significantly improved by the flavonoids after ULD-assisted treatment. Notably, the emulsions prepared using MP-Api/CNs contained smaller oil droplets and exhibited better emulsifying properties, compared to emulsions prepared with MP-Mor/CNs or MP-Que/CNs. This study is essential for ULD-assisted treatment since the processing impact may be increased by choosing the most suitable flavonoid.

Emulsion templated scaffolds of poly(ε-caprolactone) - a review

The role of poly(ε-caprolactone) (PCL) and its 3D scaffolds in tissue engineering has already been established due to its ease of processing into long-term degradable implants and approval from the FDA. This review presents the role of high internal phase emulsion (HIPE) templating in the fabrication of PCL scaffolds, and the versatility of the technique along with challenges associated with it. Considering the huge potential of HIPE templating, which so far has mainly been focused on free radical polymerization of aqueous HIPEs, we provide a summary of how the technique has been expanded to non-aqueous HIPEs and other modes of polymerization such as ring-opening. The scope of coupling of HIPE templating with some of the advanced fabrication methods such as 3D printing or electrospinning is also explored.

Progresses in synthetic technology development for the production of L-lactide

L-Lactide is an intermediate for the industrial production of polylactic acid (PLA). The chemical and optical purities of lactide determine the quality of the prepared PLA. It is of great challenge to synthesize L-lactide efficiently with high chemical and optical purities under the conditions applicable for industrial production. With the national plastic reduction order issued, developing biodegradable materials such as PLA has gradually become a hot topic, and the production of upstream lactide is the key technique for the whole industrial chain. This mini-review aims to summarize typical works on the related synthetic technology development in recent years.

Water-in-water Pickering emulsions stabilized by the starch nanocrystals with various surface modifications

HYPOTHESIS

Using the platelet-like starch nanocrystals (SNCs) to stabilize emulsions is attractive because as-prepared emulsions have promising applications in cosmetics and food fields. Limited studies mainly focus on the oil-in-water system, and another important system, the water-in-water emulsions stabilized by SNCs, has not yet been unveiled.

EXPERIMENTS

Two surface modification strategies, crosslinking and acetylation, were applied to tune surface property and aggregation of SNCs, and a common all-aqueous system (dextran/poly(ethylene glycol)) was used here as template. The viscoelasticity and morphology of emulsions were studied in terms of the SNC loadings and polymer ratios.

FINDINGS

Crosslinking results in aggregation of SNCs, and the particle size increases (from 110 nm to 370 nm) with increased levels of substitution. This favors improving emulsifying ability of particles. Acetylation decreases the particle size (∼90 nm) and weakens the affinity of SNCs to the two aqueous phases, improving the emulsifying efficiency of SNCs. More intriguingly, the two emulsion systems show different phase inversion behaviors. The depletion-stabilization mechanism for the cross-linked SNCs and the diffusion-controlled mechanism for the acetylated SNCs are proposed using the emulsion viscoelasticity as probe. This study makes a comprehensive insight into the regulation of water-in-water emulsion morphology and types with the platelet-like SNCs.

Nanocellulose in Emulsions and Heterogeneous Water-Based Polymer Systems: A Review

Nanocelluloses (i.e., bacterial nanocellulose, cellulose nanocrystals, and cellulose nanofibrils) are cellulose-based materials with at least one dimension in the nanoscale. These materials have unique and useful properties and have been shown to assemble at oil-water interfaces and impart new functionality to emulsion and latex systems. Herein, the use of nanocellulose in both emulsions and heterogeneous water-based polymers is reviewed, including dispersion, suspension, and emulsion polymerization. Comprehensive tables describe past work employing nanocellulose as stabilizers or additives and the properties that can be tailored through the use of nanocellulose are highlighted. Even at low loadings, nanocellulose offers an unprecedented level of control as a property modifier for a range of emulsion and polymer applications, influencing, for example, emulsion type, stability, and stimuli-responsive behavior. Nanocellulose can tune polymer particle properties such as size, surface charge, and morphology, or be used to produce capsules and polymer nanocomposites with enhanced mechanical, thermal, and adhesive properties. The role of nanocellulose is discussed, and a perspective for future direction is presented.

Cellulose nanofibers reinforced biodegradable polyester blends: Ternary biocomposites with balanced mechanical properties

Blending two biodegradable aliphatic polyesters with complementary bulk properties is an easy way of tuning their final properties. In this work, the ductile poly(butylene succinate) was mixed with polylactide, and as expectable, the blends show improved toughness with sharply reduced strengths. The pristine cellulose nanofibers were then used as the reinforcement for the blends. It is found that most nanofibers are dispersed in the polylactide phase because polylactide has better affinity to nanofibers, and the lower viscosity level of polylactide also favors driving nanofibers into the continuous polylactide phase during melting mixing. In this case, the strength and rigidity losses resulted from the presence of soft poly(butylene succinate) phase are compensated to some extent. To further improve mechanical properties, a two-step approach (reactive processing of blends, followed by the incorporation with nanofibers) was developed. This work provides an interesting way of fabricating fully biodegradable composites with well-balanced mechanical performance.

Microfibrillated Cellulose Suspension and Its Electrorheology

Microfibrillated cellulose (MFC) particles were synthesized by a low-pressure alkaline delignification process, and their shape and chemical structure were investigated by SEM and Fourier transformation infrared spectroscopy, respectively. As a novel electrorheological (ER) material, the MFC particulate sample was suspended in insulating oil to fabricate an ER fluid. Its rheological properties—steady shear stress, shear viscosity, yield stress, and dynamic moduli—under electric field strength were characterized by a rotational rheometer. The MFC-based ER fluid demonstrated typical ER characteristics, in which the shear stresses followed the Cho–Choi–Jhon model well under electric field strength. In addition, the solid-like behavior of the ER fluid was investigated with the Schwarzl equation. The elevated value of both dynamic and elastic yield stresses at applied electric field strengths was well described using a power law model (~E^1.5). The reversible and quick response of the ER fluid was also illustrated through the on–off test.

Melt-processing of cellulose nanofibril/polylactide bionanocomposites via a sustainable polyethylene glycol-based carrier system

Considering the appealing need for an industrially viable approach, this works aims at demonstrating the rapid and easy melt processing of Polylactide (PLA) bio-composites reinforced with cellulose nanofibrils (CNF). For this purpose and against to their high propensity to self-aggregate on processing, an aqueous CNF-based suspension in the presence of polyethylene glycol (PEG) followed by a gentle drying way were performed to provide melt-processable CNF-based masterbatches. Morphological observations coupled with rheological analyses confirmed how the strategy of the PEG-based masterbatch approach facilitated the formation of a well-dispersed and strongly interacting CNF network within the polymeric matrix. At temperatures above T_g, thermo-mechanical characterization showed that the load-bearing capacity of the web-like CNF network was even more apparent and counteracted the PEG plasticizing effect. Thermogravimetric analysis evidenced that in the case of selective positioning at the PLA-PEG interface, CNF mitigated the negative impact of PEG addition on the PLA thermal stability. These results revealed the successfulness of our sustainable organic solvent-free approach to prepare melt-processable CNF masterbatches, which can be readily converted into conventional industrially scalable melt-processing techniques.