Novel stable pickering emulsion based solid foams efficiently stabilized by microcrystalline cellulose/chitosan complex particles

Fabrication of water/oil-resistant paper by nanocellulose stabilized Pickering emulsion and chitosan

Developing plastic/fluorine/silicon-free and degradable water/oil-resistant coatings for paper-based packaging materials to replace disposable plastic products is a very effective way to solve the problem of 'white pollution' or microplastics pollution. A novel water/oil-resistant coating was developed by alkyl ketene dimer (AKD)-based Pickering emulsion and chitosan in this work. Cellulose nanofibrils (CNF) were used as a stabilizing solid for AKD emulsion, with the addition of chitosan as an oil-resistance agent. The coating provides excellent hydrophobicity, water/oil resistance as well as good barrier properties. The water contact angle was as high as 130° and the minimum Cobb60 value was 5.7 g/m2, which was attributed to the hydrophobicity of AKD. In addition, the kit rating reached maximum 12/12 at coating weight of 8.26 g/m2 and the water vapor transmittance rate (WVTR) was reduced to 153.4 g/(m2⋅day) at the coating weight of 10.50 g/m2. The tensile strength of the paper was increased from 28.1 to 43.6 MPa after coating. Overall, this coating can effectively improve the performance of paper-based materials, which may play an important role in the process of replacing disposable plastic packaging with paper-based materials.

Porous superabsorbent composites prepared from aqueous foam template and application evaluation

Rapid water absorption is very important for the application of superabsorbent polymers under dry or semi-dry conditions, but there are currently few relevant studies. In this context, a novel porous superabsorbent of chitosan-grafted acrylic copolymer-2-acrylamido-2-methylpropanesulfonic acid/sapindus mukorossi pericarp/calcined oil shale semi-coke (CS-g-P(AA-co-AMPS)/SMP/COSSC) was prepared by a green and convenient foam template method, which was triggered by redox polymerization. The rich pore structure of the porous superabsorbent was conducive to accelerating the water absorption rate. It only took 15 min to reach a swelling capacity of 650 g g-1 in distilled water. Soil experiments show that even with the addition of 0.5 wt% porous superabsorbent, the soil water retention time can be extended to 7 days. Finally, it was applied to the growth of cabbage seeds and it was found that the growth was significantly improved. Based on these excellent properties, we expect to provide a valuable reference for the preparation of fast-absorbing materials through the green water-based foam template method, contributing to sustainable agriculture.

An overview of edible foams in food and modern cuisine: Destabilization and stabilization mechanisms and applications

Foam, as a structured multi-scale colloidal system, is becoming increasingly popular in food because it gives a series of unique textures, structures, and appearances to foods while maintaining clean labels. Recently, developing green and healthy food-grade foaming agents, improving the stability of edible foams, and exploring the application of foam structures and new foaming agents have been the focus of foam systems. This review comprehensively introduces the destabilization mechanisms of foam and summarizes the main mechanisms controlling the foam stability and progress of different food-grade materials (small-molecular surfactants, biopolymers, and edible Pickering particles). Furthermore, the classic foam systems in food and modern cuisine, their applications, developments, and challenges are also underlined. Natural small-molecular surfactants, novel plant/microalgae proteins, and edible colloidal particles are the research hotspots of high-efficiency food-grade foam stabilizers. They have apparent differences in foam stability mechanisms, and each exerts its advantages. However, the development of foam stabilizers remains to be enriched compared with emulsions. Food foams are diverse and widely used, bringing unique enjoyment and benefit to consumers regarding sense, innovation, and health attributes. In addition to industrial inflatable foods, the foam foods in molecular gastronomy are also worthy of exploration. Moreover, edible foams may have greater potential in structured food design, 3D/4D printing, and controlled flavor release in the future. This review will provide a reference for the efficient development of functional inflatable foods and the advancement of foam technologies in modern cuisine.

Pickering emulsions as an effective route for the preparation of bioactive composites: A study of nanocellulose/polyaniline particles with immunomodulatory effect

Several studies have reported on application of cellulose particles for stabilizing Pickering emulsions (PE). Here we employ an original approach that involves using these particles as a part of advanced composite colloids made of conducting polymer polyaniline (PANI) and cellulose nanocrystals (CNC) or nanofibrils (CNF). PANI/cellulose particles were prepared using oxidative polymerization of aniline in situ in the presence of CNC or CNF. The type and amount of celluloses (CNC vs CNF) and concentration of precursors (aniline monomer and oxidant) used in the reaction determined properties of the colloidal particles, such as size, morphology and content of PANI. The particles demonstrated intriguing biological characteristics, including no cytotoxicity, antibacterial activity against Staphylococcus aureus and Escherichia coli, antioxidant activity and related immunomodulatory activity. For the first time, such composites were used to successfully stabilize oil-in-water PE with undecane or capric/caprylic triglyceride oils. The properties of the emulsions were determined by the PANI/cellulose particles and oil used. The key finding of the study is the demonstrated ability of PANI/cellulose particles to stabilize PE, as well as the excellent antioxidant activity and ROS scavenging action originating from PANI presence, indicating potential of such systems for use in biomedicine, particularly for wound healing.

Insight into the composite assembly process, nanofibril structure and stability of undenatured type II collagen in the presence of different types of nanocelluloses

Four types of nanocelluloses (CNs), including cellulose nanocrystals (CNC), cellulose nanofibrils (CNF), cationic etherified nanocellulose (CCNF) and TEMPO-oxidized nanocellulose (TOCNF), were incorporated into the assembly process of undenatured type II collagen (UC-II). In the presence of CNs, the kinetics of UC-II composite assembly slightly fluctuated and the magnitude of UC-II assembly increased (from 59.93 to 66.83-85.06 %). CNC and CNF disrupted the triple helix structure of UC-II while CCNF and TOCNF had weak impact on it. Hydrogen bonding and hydrophobic interactions were dominant driving forces of UC-II/CNs, and electrostatic interactions were also involved in the fabrication of UC-II/CCNF and UC-II/TOCNF. UC-II/CNs exhibited distinct nanostructures due to the differences in shape, level, and surface group of CNs. CCNF and TOCNF contributed to the enhanced physical stability due to the increased surface charge. In addition, the thermal stability and rheological properties of UC-II/CNs were also improved. The composite assembly process, nanofibril structure and stability of UC-II in the presence of different types and levels of CNs, which was useful to develop the novel composite nanofibrils for the application in functional foods.

Chitosan particles modulate the properties of cellulose nanocrystals through interparticle interactions: Effect of concentration

The physical and chemical properties of cellulose nanocrystals (CNC) were regulated by physical crosslinking with chitosan particles (CSp). At a fixed concentration (0.5 wt%) of CNC, varying CSp concentration (0.02-0.5 wt%) influenced the morphologies and chemical properties of the obtained complex particles (CNC-CSp). The results of Fourier transform infrared spectroscopy (FTIR) and zeta potential confirmed the electrostatic and hydrogen bonding interactions between CSp and CNC. At a low CSp concentration (0.02-0.05 wt%), the charge shielding effect induced the formation of particle aggregation networks, thus showing increased viscosity, turbidity and size (153.4-2605.7 nm). At a higher CSp concentration (0.1-0.5 wt%), the hydrogen bonding interaction promoted CSp adsorption onto the surface of CNC, thus facilitating the dispersion of CNC-CSp due to electrostatic repulsion caused by surface-adsorbed CSp. In addition, CSp improved the thermal stability, hydrophobicity (41.87-60.02°) and rheological properties of CNC. Compared with CNC, CNC-CSp displayed a better emulsifying ability and emulsion stability, in which CSp could play a dual role (i.e., charge regulator and stabilizer). This study suggests that introducing CSp can improve the properties and application potentials of CNC as food colloids.

Recent developments in improving the emulsifying properties of chitosan

Chitosan is one of the valuable products obtained from crustacean waste. The unique characteristics of chitosan (antimicrobial, antioxidant, anticancer, and anti-inflammatory) have increased its application in various sectors. Besides unique biological properties, chitosan or chitosan-based compounds can stabilize emulsions. Nevertheless, studies have shown that chitosan cannot be used as an efficient stabilizer because of its high hydrophilicity. Hence, this review aims to provide an overview of recent studies dealing with improving the emulsifying properties of chitosan. In general, two different approaches have been reported to improve the emulsifying properties of chitosan. The first approach tries to improve the stabilization property of chitosan by modifying its structure. The second one uses compounds such as polysaccharides, proteins, surfactants, essential oils, and polyphenols with more wettability and emulsifying properties than chitosan's particles in combination with chitosan to create complex particles. The tendency to use chitosan-based particles to stabilize Pickering emulsions has recently increased. For this reason, more studies have been conducted in recent years to improve the stabilizing properties of chitosan-based particles, especially using the electrostatic interaction method. In the electrostatic interaction method, numerous research has been conducted on using proteins and polysaccharides to increase the stabilizing property of chitosan.

Thermal insulation and antibacterial foam templated from bagasse nanocellulose /nisin complex stabilized Pickering emulsion

Foam packaging with good thermal insulation and antibacterial properties is promising for cold chain delivery to strengthen food safety. This study reports a novel antibacterial foam with thermal insulation templated from bagasse nanocellulose complex particle-stabilised acrylate epoxy soybean oil (AESO) Pickering emulsions. Nanocellulose/nisin complex particles (N-CNFs) were prepared by loading positively charged nisin onto negatively charged cellulose nanofibrils via electrostatic interactions, that highly enhanced the stability of nanocellulose at the AESO/water interface and imparted the corresponding foam with good antibacterial properties. The results show that the porosity of the foam prepared with N-CNFs increased from 10.9% to 29.9% compared with that of the foam corresponding with bare nanocellulose; the thermal conductivity of the N-CNF foam decreased substantially from 0.431 W/m·K to 0.197 W/m·K. Moreover, the prepared foam exhibited good antibacterial activity, and its bacteriostatic rate against Listeria monocytogenes was 91.33%. The incorporation of antibacterial peptides into nanocellulose has enriched the study of the Pickering emulsion templating method for preparing multifunctional foam materials and is expected to broaden the application of nanocellulose in the field of food packaging.

Progress in the Application of Food-Grade Emulsions

The detailed investigation of food-grade emulsions, which possess considerable structural and functional advantages, remains ongoing to enhance our understanding of these dispersion systems and to expand their application scope. This work reviews the applications of food-grade emulsions on the dispersed phase, interface structure, and macroscopic scales; further, it discusses the corresponding factors of influence, the selection and design of food dispersion systems, and the expansion of their application scope. Specifically, applications on the dispersed-phase scale mainly include delivery by soft matter carriers and auxiliary extraction/separation, while applications on the scale of the interface structure involve biphasic systems for enzymatic catalysis and systems that can influence substance digestion/absorption, washing, and disinfection. Future research on these scales should therefore focus on surface-active substances, real interface structure compositions, and the design of interface layers with antioxidant properties. By contrast, applications on the macroscopic scale mainly include the design of soft materials for structured food, in addition to various material applications and other emerging uses. In this case, future research should focus on the interactions between emulsion systems and food ingredients, the effects of food process engineering, safety, nutrition, and metabolism. Considering the ongoing research in this field, we believe that this review will be useful for researchers aiming to explore the applications of food-grade emulsions.

Preparation of soybean dreg fiber solid emulsifier and its effect on the stability of Pickering emulsion

High purity insoluble dietary fiber (HPIDF) was extracted from Okara by compound enzyme method, and solid emulsifiers with different particle sizes were prepared by wet grinding. Its composition, structure and physicochemical properties were studied, and the influence mechanism of solid emulsifiers with different particle sizes on emulsifying properties and interface stability of Pickering emulsion was systematically studied. The results showed that the particle size of HPIDF decreased significantly, the ζ-potential, contact Angle and swelling capacity of HPIDF ncrease significantly (p < 0.05). HPIDF forms an adsorption layer at the oil-water interface, and some of them are connected to form a bridge network structure, which plays a role of steric hindrance. And the emulsion has excellent stability under different environmental factors. HPIDF are suitable raw materials as natural food-grade solid emulsifiers. It is cost-effective and eco-friendly to realize the high-value utilization of Okara resources, reduce resource waste, and extend the industrial chain.

Microalgae Chlorella vulgaris and kraft lignin stabilized cellulosic wet foams for camouflage

Plants, animals, and humans use camouflage to blend in with their surroundings. The camouflage is achieved with different combinations of colors, patterns, and morphologies. In stealth applications, the simplest camouflage uses textiles colored similarly to the environment to create an illusion. However, often, visible light range camouflage is not enough since the multispectral detection technologies of today are readily utilized for identification. Foams can be created with a straightforward fabricating process, and lightweight material exhibits good thermal insulation properties, providing stealth in the infrared light region. Herein, we produce cellulosic wet foams from surfactant and bleached pulp or cellulose nanofibrils. The visible light camouflage is created with green microalgae, Chlorella vulgaris, and brown kraft lignin, which also stabilized the foams. The thermal and spectral camouflage performance of foams was influenced by the cellulose content as well as the stability and water content of foams. Overall, these results give insight into how stability impacts the thermal and spectral properties of wet foams and provide a solid base for further material development to improve camouflage performance. While there is plenty of data on dry foams, the functional behavior of wet foams is currently not well known. Our method, using plant-based components can be exploited in a variety of other applications where simplicity and scalability are important.

A green initiative for oiled sand cleanup using chitosan/rhamnolipid complex dispersion with pH-stimulus response

The released oil can affect the vulnerable shoreline environment if the oil spills happen in coastal waters. The stranded oil on shorelines is persistent, posing a long-term influence on the intertidal ecosystem after weathering. Therefore, shoreline cleanup techniques are required to remove the oil from the shoreline environment. In this study, a new shoreline cleanup initiative using chitosan/rhamnolipid (CS/RL) complex dispersion with pH-stimulus response was developed for oiled sand cleanup. The results of factorial and single-factor design revealed that the CS/RL complex dispersion maintained high removal efficiency for oiled sand with different levels of oil content in comparison to using rhamnolipid alone. However, the increase of salinity negatively affected the removal efficiency. The electrostatic screening effect of high ionic strength can hinder the formation of the CS/RL complex, and thus reduce removal efficiency. The pH-responsive characteristic of chitosan allows the easy separation of water and oil in washing effluent. The chitosan polyelectrolytes aggregated and precipitated due to the deprotonation of amino groups by adjusting the pH of the washing effluent to above 8. The microscope image demonstrated that the chitosan aggregates wrapped around the oil droplets and settled to the bottom together, thus achieving oil-water separation. Such pH-stimulus response may help achieve an easy oil-water separation after washing. These findings have important implications for developing the new strategies of oil spill response.

Pesticide-loaded colloidal nanodelivery systems; preparation, characterization, and applications

The fast developments in pesticide-loaded nanodelivery systems over the last decade have inspired many companies and research organizations to highlight potential applications by employing encapsulation approaches in order to protect the agricultural crops. This approach is being used to retard the indiscriminate application of conventional pesticides, as well as, to make ensure the environmental safety. This article shed light on the potential of colloidal delivery systems, particularly controlled releasing profiles of several pesticides with enhanced stability and improved solubility. Colloidal nanodelivery systems, being efficient nanoformulations, have the ability to boost up the pest-control competence for prolonged intervals thru averting the early degradation of active ingredients under severe ecofriendly circumstances. This work is thus aimed to provide critical information on the meaningful role of nanocarriers for loading of pesticides. The smart art of pesticide-loaded nanocarriers can be more fruitful owing to the use of lower amount of active ingredients with improved efficiency along with minimizing the pesticide loss. Also, the future research gaps regarding nano-pesticide formulations, such as role of nanomaterials as active ingredients are discussed briefly. In addition, this article can deliver valuable information to the readers while establishing novel pesticide-loaded nanocarriers for a wide range of applications in the agriculture sectors.

MFC/NFC-Based Foam/Aerogel for Production of Porous Materials: Preparation, Properties and Applications

Nanofibrillated cellulose and microfibrillated cellulose are potential raw materials separated from plant fibers with a high aspect ratio and excellent mechanical properties, which can be applied in various fields (packaging, medicine, etc.). They have unique advantages in the preparation of aerogels and foams, and have attracted widespread attention in recent years. Cellulose-based porous materials have good biodegradability and biocompatibility, while high porosity and high specific surface area endow them with strong mechanical properties and liquid retention performance, which can be used in wall construction, sewage treatment and other fields. At present, the preparation method of this material has been widely reported, however, due to various process problems, the actual production has not been realized. In this paper, we summarize the existing technical problems and main solutions; in the meantime, two stable systems and several drying processes are described, and the application potential of cellulose-based porous materials in the future is described, which provides a reference for subsequent research.

Cellulose and cellulose derivatives: Different colloidal states and food-related applications

Development of new sources and isolation processes has recently enhanced the production of cellulose in many different colloidal states. Even though cellulose is widely used as a functional ingredient in the food industry, the relationship between the colloidal states of cellulose and its applications is mostly unknown. This review covers the recent progress on illustrating various colloidal states of cellulose and the influencing factors with special emphasis on the correlation between the colloidal states of cellulose and its applications in food industry. The associated unique colloidal states of cellulose like high aspect ratio, crystalline structure, surface charge, and wettability not only promote the stability of colloidal systems, but also help improve the nutritional aspects of cellulose by facilitating its interactions with digestive system. Further studies are required for the rational control and improvement of the colloidal states of cellulose and producing food systems with enhanced functional and nutritional properties.

Oleogel Films Through the Pickering Effect of Bacterial Cellulose Nanofibrils Featuring Interfacial Network Stabilization

As bio-based food packaging materials promise a more sustainable future, this work fabricated edible oleofilms by casting beeswax-in-water Pickering emulsions, which were formed by the physical hybrid particles of bacterial cellulose nanofibrils (BCNFs) and carboxymethyl chitosan (CCS) (BC/CCS). The emulsion droplet size was varied from 4 to 9 μm, and the emulsion index (EI) was all up to 100%. The obtained emulsions exhibited excellent long-term stability, and there was no change in the EI (100%) after the storage of the emulsion for 3 months. Moreover, the environmental temperature had almost no impact on the droplet size and EI of the emulsion. The mechanical properties of the oleofilms were significantly improved by enhancing the content of BC/CCS. There was also a visual reduction in the water vapor permeability (WVP) value, which was lower than 1.1 × 10^-7 g·m^-1·h^-1·Pa^-1. Furthermore, the obtained oleofilms exhibited a notable improvement in surface hydrophobicity, and surprisingly, it could be easily redispersed into water to recover back to the emulsion state without additional high energy mixing. This suggested that this edible oleofilm was prepared by a fully green method by casting Pickering emulsions stabilized by BC/CCS and could extend its application for the development of food-grade coating materials.