Nanocellulose-stabilized Pickering emulsions: Fabrication, stabilization, and food applications

Excellently stable Camellia oleifera oil Pickering emulsion fabricated based on high carboxyl content cellulose nanofibrils

Nanocellulose-based Pickering emulsions offer a promising alternative to traditional emulsions in cosmetics due to their biocompatibility. However, the instability of unmodified nanocellulose-based Pickering emulsions remains an issue to be addressed. To solve this problem, cellulose nanofibrils with high carboxyl content (PT-CNFs) were prepared by a sodium periodate (NaIO4) and TEMPO two-step oxidation and employed to fabricate stable PT-CNF-based Camellia oleifera oil Pickering emulsions by ultrasonic emulsification and high-pressure homogenization techniques. The results showed the yield and carboxyl content of PT-CNFs were 52.9 % and 2.1 mmol/g, respectively. Due to the chemical and physical treatments, the PT-CNF-based emulsions had small droplet sizes and high ζ-potential values, and exhibited excellent stability. The stability of PT-CNF-based emulsions was much better than that of commonly cosmetic stabilizer hydroxyethyl cellulose (HEC) based emulsions. When the PT-CNF concentration was 0.7 wt% and oil-water ratio was 40:60, the prepared PT-CNF-based Camellia oleifera oil emulsion demonstrated superior stability at the temperature of 4 °C, and creaming index of the emulsion remained >90 % over 30 days. This study indicated that PT-CNFs had huge potential as emulsion stabilizers in the field of cosmetics, and inspired the design and development of Pickering emulsions with high stability and environmental friendliness.

A sustainable and efficient emulsifier for vegetable oil-pickering emulsion based on cellulose nanoribbons

An emulsion stabilization technique based on molecularly thin cellulose nanoribbons (CR) is described, demonstrating superior emulsifying capability at concentrations as low as 0.05 %. The results show that CR enables the stabilization of oil-in-water emulsions that remain stable for over 60 days, even at high oil-to-water ratios. Rheological assessment reveals a shear-thinning profile and dominance of storage modulus (G') over loss modulus (G"), signifying the emulsions' viscoelastic nature and resistance to structural breakdown. In particular, emulsions containing 0.5 % CR presented exceptional centrifugal stability at 8000 rpm without oil leakage or emulsion breakage. In contrast, emulsions stabilized by cellulose nanocrystals (CNC) and nanofibrils (CNF) exhibited significantly reduced stability and viscosity. This study underscores CR's potential in creating eco-friendly, high-performance food-grade emulsions that meet the burgeoning demands for environmentally friendly and healthy foods.

Emerging Applications of Pickering Emulsions in Pharmaceutical Formulations: A Comprehensive Review

Over the past two decades, particle-stabilized Pickering emulsions (PEs) have emerged as a versatile platform in pharmaceutical formulations, demonstrating distinct advantages over surfactant-based systems through enhanced stability, reduced toxicity, and tunable interfacial properties. These systems exhibit unique drug delivery potential through their precisely controllable architecture, particularly in achieving spatiotemporal drug release patterns, tissue-specific targeting, and enhanced therapeutic payload encapsulation. In this review, the characteristics of PEs are first detailed, followed by an introduction to the main preparation methods and the key parameters for controlling the type, droplet size, and stability of PEs. The third section categorizes and discusses the advantages and disadvantages of various solid particles as emulsifiers. Lastly, emphasis is placed on the application of PEs in the pharmaceutical field, including functionalized designs and various administration routes to enlighten the rational design of PEs for effective drug delivery.

Enhancement of konjac glucomannan/carrageenan blend films by incorporating cellulose nanocrystals/tannic acid stabilized Litsea cubeba essential oil Pickering emulsion and their application to pork preservation

With increasing demands for environmental protection and food safety, biodegradable active food packaging is gaining attention. Hereby, konjac glucomannan/carrageenan blend films (KCNTO) incorporating Litsea cubeba essential oil (LCEO) Pickering emulsion stabilized by cellulose nanocrystals/tannic acid were developed and evaluated for their preservation effect on pork. The formation, structure, physical properties, antioxidant and antimicrobial activities of KCNTO, as well as the release of LCEO were investigated. The results showed that the viscosity and pseudoplasticity of KCNTO film-forming solutions decreased due to LCEO Pickering emulsion interfering with the molecular entanglement network of konjac glucomannan/carrageenan. LCEO droplets were homogeneously distributed in KCNTO to make its structure loose. Hydrogen bonding interactions occurred between LCEO Pickering emulsion and the film matrix. The addition of LCEO Pickering emulsion improved KCNTO's elongation at break, water contact angle, water vapor barrier and UV shielding, while giving it excellent antioxidant and antimicrobial activities. LCEO was slowly and sustainably released from KCNTO at 25 °C in air. KCNTO-8 maintained the quality of pork by slowing down the increase in pH, aerobic plate count and thiobarbituric acid reactive substances during storage at 4 °C. The findings suggested that KCNTO was a promising active packaging material for pork preservation.

The properties of Pickering emulsions stabilized by bacterial cellulose nanofibrils and its retarding effect on lipid digestion

The rate of lipid digestion can be delayed by the interface modulation of O/W Pickering emulsions. In this study, bacterial cellulose nanofibrils prepared by ball milling synergized with electron beam irradiation (B-IB50) were used as stabilizers to prepare Pickering emulsions. Results showed that B-IB50 formed emulsion systems with good stability. Especially when the content of B-IB50 was >0.6 wt%, emulsions showed excellent storage and environmental stability. Notably, at pH 2.0, the electrostatic repulsion between fibrils was weakened leading to closer cross-linking and giving better protection to the oil droplets. When the content of B-IB50 in emulsions increased from 0.2 wt% to 1.0 wt%, the release of FFA decreased from 66.7 % to 37.8 % during digestion, which indicated that the presence of more B-IB50 inhibited the digestion of lipids. Main mechanisms were proposed for the results: (1) B-IB50 formed a dense interface layer that reduced the binding area of bile salts and lipases; (2) B-IB50 formed the three-dimensional network structure limiting the displacement of bile salts and lipases, thereby reducing the binding to lipids. This study provided theoretical ideas for developing emulsion-based functional foods with lipid-reducing effects.

Pickering emulsion stabilized by salmon protein-fucoidan complex and its absorption promotion effect on astaxanthin

In this experiment, salmon protein-fucoidan complexes (SMP-FU) were used to stabilize Pickering emulsions encapsulating astaxanthin (AXT). The hydrophobic forces and hydrogen bonding between SMP and FU were revealed as the main interaction to form the SMP-FU complex. The addition of FU led to the increase of three-phase contact angle from 51.3° to 92.1°, and the best hydrophilic-hydrophobic balance was achieved with 2 % FU. The emulsions stabilized by SMP-FU became more homogeneous and denser with the increase of FU concentration, and the smallest droplet size was obtained in the emulsion stabilized by SMP-FU(2 %), which exhibited good rheological properties and acceptable stabilities under the heating, strong ionic strength and extreme acid-base conditions. AXT loaded Pickering emulsion (PEAs) stabilized by SMP-FU (SMP-FU-PEAs) provided better protection for AXT and improved the AXT retention rate under different storage condition, and displayed better gastric acid stability and higher AXT release rate (60.57 %) and bioaccessibility index (71.52 %) in than SMP-PEAs during in vitro digestion. The Caco-2 cell assay and in vivo experiments revealed a significant increase in the uptake rate of AXT embedded in SMP-FU-PEAs, which provided a feasible way to subsequently promote the uptake and utilization of the active substance.

Bifunctional performance of cellulose nanofibers grafted with polyhexamethylene guanidine in Pickering emulsion: Antibacterial activity and interfacial stability

This study developed the multifunctional cellulose nanofibers (CNFs) as emulsifier for preparation of antibacterial, ultrastable and non-toxic emulsion. To achieve these properties, CNFs were oxidated using sodium periodate to introduce aldehyde groups, which served as Schiff-base reaction sites for amino groups of polyhexamethylene guanidine (PHMG), yielding PHMG-grafted CNFs (PCNFs). The modified CNFs retained good emulsification ability while acquiring antibacterial properties. PCNFs were irreversibly absorbed onto the droplet surface, forming dense covering layers that prevented coalescence. Their strong entanglement and bridging flocculation capacities bonded adjacent droplets, creating stable droplet-fiber network structures. This enabled a creaming index of 90 % with only 4.0 % PCNFs. Emulsion stabilized by PCNFs achieved over 99 % antibacterial rate and 99 % cell viability, confirming their effective inactivation of bacteria and good biocompatibility. These findings showed the potential of PCNFs for developing antibacterial, ultrastable, and non-toxic emulsions for daily and biomedical applications.

Research progress on improving dispersion stability of nanocellulose in different media: A review

Nanocellulose has been widely used in various fields due to its good biocompatibility, mechanical properties, large specific surface area and environmental friendliness. Among these applications, uniformly dispersing nanocellulose in various media to improve its performance is an application with good development prospects. However, due to the presence of surface hydroxyl groups, nanocellulose tends to form aggregates between molecular chains and is less compatible with nonpolar solvents, thus making it difficult to be stably dispersed in solvents. How to break the aggregation between cellulose and improve its compatibility with the medium has become a challenging issue. In this paper, the dispersion system is classified into polar medium, nonpolar medium and polymer matrix according to the polarity and state of the medium, and a review is presented on how to improve the dispersion stability of nanocellulose in different media. The methods of using surface modification to improve the dispersion stability of nanocellulose in different media, such as carboxylation, amidation, and grafting of long-chain molecules to reduce the aggregation among nanocellulose and to improve the compatibility with solvents, are highlighted. Finally, suggestions are made for future research directions.

Cellulose-based delivery systems for bioactive ingredients: A review

Considering the outstanding advantages including abundant resources, structure-performance designability, impressive mechanical strength, and 3D network structure-forming ability, cellulose is an ideal material for encapsulating bioactive ingredients. Due to its low solubility in water, large-scaled morphology and poor flexibility, cellulose is unsuitable for the construction of carriers. Consequently, the majority of cellulose is employed following physical or chemical modification. Cellulose and its derivatives are extensively employed in the food industry, including fat replacement, food packaging composites, food additives, 3D-printed food and delivery systems. Their benefits in food delivery systems are particularly pronounced. Therefore, the distinguishing features, preparation methods, recent developments and effectiveness of different cellulose-based delivery systems for bioactive ingredients are discussed. Cellulose-based delivery systems offer unique advantages in terms of environmental impact reduction, modification facilitation, stimuli-responsive release as well as tailored design, and their application has gained widespread recognition. However, they are facing challenges in the application process comprising modification methods for cellulose-based materials, new methods for commercial preparation on a wide scale, cellulose-based multifunctional conveyance systems and systematic evaluation using in vivo experiments. In conclusion, this review provides theoretical references for the development of novel delivery carriers as well as the efficient application and popularization of cellulose-based delivery systems.

Oil-in-water Pickering emulsions with Buriti vegetable oil stabilized with cellulose nanofibrils: Preparation, stability and antimicrobial properties

Mauritia flexuosa (Buriti) vegetable oil (OV) has attracted technological interest in various sectors, including pharmaceuticals, food, and beverages, because of its excellent antioxidant activity. The active OV components are fatty compounds, and stability is required for proper application. In this work, we investigated OV-in-water Pickering emulsions stabilized by cellulose nanofibrils (CNF). CNF is sustainable, economically viable, and environmentally friendly, and it is suitable for developing products in an eco-friendly way. The factorial design of experiments (DoE) indicates that the amount of CNF and the homogenization time significantly affect the emulsion, preventing coalescence over 30 days. Fourier-transform Raman spectroscopy (FT-Raman) and Fourier-transform infrared spectroscopy (FTIR) show that CNF stabilizes the OV droplets through induced dipole-dipole interactions and hydrogen bonds. Rheological analysis was relevant to the relationship between internal microstructure strength and viscous flow behavior of the emulsions. A novel approach enabled the identification of the CNF stabilization mechanism in the emulsion system via fluorescence microscopy. Diameter distribution measurements and steady-state rheological tests indicate that the emulsions have good stability at room temperature and suitable steady-state viscosity for food applications and beverage products as they show pronounced shear thinning behavior for cream and lotion skin care products.

Insoluble dietary fiber stabilized Pickering emulsions as novel food ingredients: Preparation, potential applications and future perspectives

Pickering emulsions (PEs) are valued in the food industry for their biocompatibility and stability. Insoluble dietary fiber (IDF), a sustainable and low-toxicity stabilizer derived from agricultural by-products, has shown great potential for food applications. This paper reviews advancements in IDF extraction and its use in creating IDF-based PEs (IDF-PEs). Key applications in the food sector include food packaging, 3D printing, fat substitution, bioactive delivery, and food stabilization. IDF's natural stabilizing properties and environmentally friendly extraction from agricultural waste are emphasized. While challenges remain regarding the stability and safety of IDF-PEs in complex food systems, their versatility and broad application potential make them a promising area of research. This study provides insights into developing sustainable, multifunctional food ingredients, aiming to expand the use of IDF-PEs and contribute to global sustainability goals.

PDMS-in-water emulsions stabilized by cellulose/chitin/starch nanoparticles for fabrication of oil adsorbents: A comparison study

Pickering emulsion template has aroused attention in the fabrication of porous composite materials. In this work, six nanoparticles including cellulose nanofiber/nanocrystal (CNF/CNC), chitin nanofiber/nanocrystals (ChNF/ChNC) and waxy/normal corn nanocrystal (WSNC/CSNC) were comparatively studied for their performance in fabricating porous composites with PDMS via Pickering emulsion templates. Among all, CNF and ChNF exhibited best emulsion stabilizing ability, while ChNF and ChNC at optimized concentrations enabled the formation of high internal phase emulsions with long-term stability of over 300 days. WSNC and CSNC with poorest emulsion stabilizing ability failed to obtain porous composites while the other four particles all formed porous composites with PDMS. The ChNF and ChNC composites displayed highest hydrophobicity, followed by the CNC composite. As adsorbents for diesel oil, the ChNF composite showed the highest adsorption capacity and adsorption selectivity, which could be easily recycled by simple mechanical squeezing. At optimized PDMS fractions, the ChNF composite could achieve continuous oil-water separation under vacuum with a highest separation efficiency of 98.9 % at high flux of 8862 L/h·m2. This study revealed the association between nanoparticles and their composite materials fabricated from Pickering emulsion template, hopefully broadening the application of natural polymers in water treatment and related fields.

A novel emulsifier for Pickering emulsion composed of whey protein and OSA-pectin loaded with Monascus pigments

Protein-polysaccharide complex carrier can solve the problem of insufficient stability of Monascus pigments (MPs), a kind of natural pigments, against heat and light. It also has the function to stabilize Pickering emulsion (PE) that can be used as fat replacer in meat products. In this study, heat denatured whey protein (HWP) and pectin modified by octenyl succinic anhydride (OSA-pectin) were prepared into complex by adding Ca2+ loaded with MPs. The complex carrier significantly enhanced the light and heat stabilities of MPs and exhibited excellent wettability. It was then used to prepare PE (HOCM-PE) as a fat replacer to improve the color performance of meat patties. The microstructure and rheological properties of HOCM-PE clarified that the main stable mechanism was to form network structure wrapped around oil droplets in the continuous phase. This structure conferred excellent viscoelasticity and stability to the emulsion. The key quality parameters of meat patties showed that HOCM-PE as a fat substitute was able to maintain the textural properties of the meat patties while providing bright red color. The research provided an ideal dual-functional emulsion for the development of low-fat and low-nitrite meat products.

A Bio-Redox Dynamic Pickering Emulsion from Nature to Nature

The biosafety issue of Pickering emulsions has gradually become public. It is shown that the particles that make up Pickering emulsions, previously thought to be non-physiologically toxic, may also pose a potential threat to human life and health, as well as to ecosystems, due to their inherent emulsifying capacity. Hence, the principle of "from nature to nature" is proposed, which refers to emulsifiers that are of natural origin and can be metabolized by natural biological processes to eliminate their emulsifying ability. A feasible pathway by which the natural small molecule, thioctic acid, is exploited for the preparation of Pickering emulsions is also presented. The strategy of calcium ion-induced aggregation and ring-opening polymerization of sodium thioctate is utilized for the preparation of particulate emulsifiers, thus forming stable O/W-type Pickering emulsions. Benefiting from the antioxidant property of the thioctic acid moiety and the transdermal capacity of the emulsion itself, it combines protection of the bioactive substance with transdermal delivery. Furthermore, the particulate emulsifiers that are prepared, abundantly enriched with dynamic disulfide bonds, can be integrated into the natural metabolic pathway, specifically by being reduced through the involved glutathione, thereby facilitating their natural degradation and effectively mitigating any potential biological hazards.

Pickering Emulsion-Based Gels with Halloysite as a Stabilizer: Formulation, Mechanical Properties and In Vitro Drug Release Studies

Lidocaine is an analgesic agent frequently incorporated in topical formulations intended for application in minor surgical procedures or relieving neuropathic pain associated with numerous conditions, including post-herpetic neuralgia or diabetic peripheral neuropathy. In this study, Pickering o/w emulsions with halloysite nanotubes as a stabilizing agent and lidocaine incorporated in the internal phase were formulated with the use of the Quality by Design (QbD) approach. The selected emulsions were transformed into semisolid gels with poloxamer 407 as a thickening agent, and investigated for rheological and textural properties, indicating the mechanical features of the obtained gels. Moreover, the obtained formulations were tested for lidocaine release with the use of vertical Franz diffusion cells in order to assess the relationship between the applied composition and potential clinical applicability of the analyzed gels. The obtained results indicate that the emulsion droplet diameter is affected mostly by the oil and halloysite contents. The yield stress points, hardness and cohesiveness values of the obtained gels increased with the oil content. The drug release rate seems to be affected mostly by the concentration of the active ingredient in the oil phase.

Pickering Emulsions Stabilized by a Naturally Derived One-Dimensional All-In-One Hybrid Nanostructure

Colloidal particles generated from plant-derived proteins and polysaccharides have high potential as particulate stabilizers since they are environmentally friendly, biocompatible, and biodegradable. It has also been shown that amphiphilic anisotropic particles are more effective particulate stabilizers at the oil/water interface. In this study, a one-dimensional all-in-one zein nanoparticle/cellulose nanofiber hybrid nanostructure (ZCHN) was successfully prepared by self-assembling hydrophilic cellulose nanofibers (CNFs) and hydrophobic zein nanoparticles (ZNPs). The synthetic approach is based on the antisolvent-induced deposition of uniform and discrete ZNPs on the surface of CNFs, with the electrostatic interaction between the two thought to be the main factor for their binding. Furthermore, the microstructure of the generated ZCHN can be easily tuned by the initial mass ratio of zein and CNFs. When compared to ZNPs or CNFs alone or their simple mixture, the emulsion stabilized with ZCHN displayed better long-term, high-temperature, and centrifugation stability. The efficient reduction of oil/water interfacial tension, neutral wettability, and more uniform and high coverage of ZCHN on the droplet surface were the reasons for such better emulsion stability. As an illustration, the resulting emulsion protected β-carotene effectively, exhibiting a significant improvement in stability under UV radiation and high temperature. Therefore, the prepared biocompatible Pickering emulsion is anticipated to have promising applications for the preservation and delivery of fat-soluble bioactive compounds.

Corn Stover-derived nanocellulose and lignin-modified particles: Pickering emulsion stabilizers and potential quercetin sustained-release carriers

Pickering emulsions (PEs) have wide applications in delivering nutraceuticals. However, the impact of extracting nanocellulose from corn stover on stabilizing PEs and delivering nutraceuticals remains unclear. In this study, four types of nanocellulose, cellulose nanocrystals (CNC), cellulose nanofibers (CNF), lignin-containing cellulose nanocrystals (LCNC), and lignin-containing cellulose nanofibers (LCNF) were successfully prepared from corn stover, an agricultural waste. Among them, LCNC and LCNF exhibited stable reticulated microstructures, lower crystallinity, and excellent thermal stability. Besides, lignin enhanced the nanoparticles' hydrophobicity, promoting the formation of more ideally amphiphilic particles, resulting in denser emulsions at the oil-water interface. Furthermore, emulsions stabilized by LCNC and LCNF demonstrated remarkable resistance to quercetin degradation under UV light exposure (with residual level exceeding 90 %) and improved quercetin's bioaccessibility during the in vitro digestion tests, achieving the highest bioaccessibility of 48.3 %. This study provided an innovative perspective on utilizing stover-derived materials for stabilizing PEs and delivering lipophilic nutrients.

Study on the mechanism of polyphenols regulating the stability of pea isolate protein formed Pickering emulsion based on interfacial effects

To improve the stability of pea isolate protein (PPI) Pickering emulsions, this study compared the stability effects of tannic acid (TA), epigallocatechin gallate, and gallic acid on PPI, and found PPI-TA the strongest binding and the best stability. When TA concentration increased from 0 to 0.5 mmol/L, the average particle size, zeta potential, and surface hydrophobicity of PPI-TA particles decreased by 23.1 %, 17.1 %, and 63.3 % respectively. The highest viscosity and elastic storage modulus G' which was also higher than and parallel to the loss modulus G", and the lowest Turbiscan stability index were observed in the emulsion with 0.5 mmol/L TA, indicating an elastic-based gel-like texture. The concentrations of conjugated diene and thiobarbituric acid reactive substances (TBARS) were also reduced by more than 58 %, showing improved oxidative stability. The study provides new insights into the interfacial behavior of PPI-polyphenols and technical support for their applications in food industry.

Lignin-containing cellulose nanocrystals from maple leaves: A natural Pickering emulsion stabilizer for food preservation

Cellulose nanocrystals have been obtained from maple leaves for stabilizing Pickering emulsions, but a chemical modification is required to improve hydrophobicity and the yield is relatively low due to the removal of non-cellulose components. Herein, lignin was retained while isolating cellulose from maple leaves, and the prepared lignin-containing cellulose nanocrystals (LCNCs) were applied as natural Pickering emulsion stabilizers. Rod-like shaped LCNCs with tunable lignin contents had suitable hydrophobicity and high aspect ratios, resulting in long-term stability of LCNC-stabilized Pickering emulsions. The obtained emulsions provided good encapsulation and protection of cinnamaldehyde, and the controlled release of cinnamaldehyde promoted sustained antibacterial efficacy. Both direct-contact and non-contact preservation modes were investigated for shrimp preservation, where headspace release of cinnamaldehyde from emulsions at non-contact mode was more effective in inhibiting bacterial proliferation compared to direct-contact (spray-coating) mode. This work demonstrates the feasibility of developing value-added LCNCs from maple leaves as sustainable Pickering emulsion stabilizers.

Application potential of wheat bran cellulose nanofibers as Pickering emulsion stabilizers and stabilization mechanisms

In this paper, cellulose nanofibers (CNF) were prepared from wheat bran (WB) and the structure of CNF was determined. Fourier transform infrared spectra and X-ray diffractograms showed the groups such as hydroxyl and carboxyl groups and cellulose type 1 structure possessed by CNF, respectively. Scanning electron microscopy exhibited that CNF was filamentous and intertwined. In addition, Pickering emulsions were prepared using CNF and the physicochemical properties of the emulsions were characterized. The results showed that CNF was able to increase the zeta potential and viscosity of the emulsions, thus improving the stability of the emulsions. Moreover, CNF formed a physical barrier by adsorbing at the oil-water interface and near the oil droplets and CNF dispersed in the aqueous phase formed a network structure to restrict the movement of oil droplets, thus improving the stability of the emulsions. These findings may provide some new insights for the potential applications of WB.

Improved Emulsifying Performance of Agarose Microgels by Cross-Interfacial Diffusion of Polyphenols

Noninterface-active polysaccharides can acquire better emulsifying properties through microgelation, yet optimizing their emulsifying performance remains a significant challenge. This study introduces a novel approach to enhance the emulsifying performance of polysaccharide microgels by leveraging the cross-interfacial diffusion of polyphenols, which promotes the interfacial adsorption of microgels. Tannic acid (TA) was predispersed in oil phases and subsequently emulsified with agarose microgel (AM) suspensions, and the impacts of TA diffusion on the emulsifying performance of AMs was investigated. In addition, the transmittance profiles of oil-water biphasic systems were found to innovatively indicate the cross-interfacial diffusion of TA and the interfacial adsorption of AMs. The current results suggest that an appropriate level of TA incorporation can benefit the emulsifying performance of AMs, correlating with decreased droplet sizes and improved physical stability of the emulsion. However, excessive TA might trigger the clustering of AMs before they reach the interfacial layer, adversely affecting the emulsion stability. In conclusion, the cross-interfacial diffusion of polyphenols offers a promising strategy to overcome the stability challenges encountered in polysaccharide microgel-stabilized emulsions.

Recent trends in nanocellulose: Metabolism-related, gastrointestinal effects, and applications in probiotic delivery

Nanocellulose, a versatile and sustainable nanomaterial derived from cellulose fibers, has attracted considerable attention in various fields due to its unique properties. Similar to dietary fibers, nanocellulose is difficult to digest in the human gastrointestinal tract. The indigestible nanocellulose is fermented by gut microbiota, producing metabolites and potentially exhibiting prebiotic activity in intestinal diseases. Additionally, nanocellulose can serve as a matrix material for probiotic protection and show promising prospects for probiotic delivery. In this review, we summarize the classification of nanocellulose, including cellulose nanocrystals (CNC), cellulose nanofibers (CNF), and bacterial nanocellulose (BNC), highlighting their distinct characteristics and applications. We discuss the metabolism-related characteristics of nanocellulose from oral ingestion to colon fermentation and introduce the prebiotic activity of nanocellulose in intestinal diseases. Furthermore, we provide an overview of commonly used nanocellulose-based encapsulation techniques, such as emulsification, extrusion, freeze drying, and spray drying, as well as the delivery systems employing nanocellulose matrix materials, including microcapsules, emulsions, and hydrogels. Finally, we discuss the challenges associated with nanocellulose metabolism, prebiotic functionality, encapsulation techniques, and delivery systems using nanocellulose matrix material for probiotics. This review will provide new insight into the application of nanocellulose in the treatment of intestinal diseases and probiotic delivery.

Biocompatible Pickering emulsions and films: Unlocking the chitosan-polyvinyl alcohol synergy for multifaceted capabilities

The exciting potential of harnessing the synergy between polysaccharides and bioactive components is attracting significant scientific interest. This research paves the way for the development of novel materials that can improve human health. Therefore, current research is conducted to explore the innovative use of chitosan, polyvinyl alcohol (PVA) complex (CHN-PVA), olive oil-stabilized Pickering emulsions (PEs), and films with multifaceted applications. The sonication stabilized Pickering emulsions (PEs at different pH values 3, 5, 7, 9, and 11) exhibited decrease in particle size compared to control PEs. The pH significantly impacted the zeta potential of PEs. Fourier-transform infrared spectroscopy (FTIR) confirmed the non-covalent linkages. The antibacterial activity of the PEs revealed greater efficacy against gram-positive bacteria than gram-negative bacteria. The CHN-PVA synergy greatly impacted the mechanical properties of films, resulting in tremendous increase of tensile strength and elongation at break compared to CHN film. The PEs efficiently delivered quercetin at neutral pH. The electro spraying of PEs significantly extended strawberry shelf life. Finally, the films exhibited promising properties of adsorbent and the results depicted that pH had a significant impact on methylene blue removal. Conclusively, this investigation underscores the potential of CHN-PVA films in food, health, and environmental fields.

CO2-switchable emulsion with controllable stability and viscosity based on chitosans and cetyltrimethylammonium bromide

Emulsions have extensive applications in food, cosmetics, and agriculture, while the requirements for emulsions differ in various fields. It is a challenge for one emulsion to satisfy multiple requirements in different applications. Herein, CO2-switchable emulsions with controllable stability and viscosity were prepared by a mixture of chitosans (CS) and CTAB. After adding low concentrations of CTAB (e.g. 0.5 mM), the viscous Pickering emulsions stabilized by CS alone were converted into moderate-viscous Pickering emulsions due to the competition adsorption between CS aggregates and CTAB at the oil-water interface. The transformation of emulsion types (such as Pickering and conventional emulsions) and the emulsion's stability and viscosity were controlled by CO2/N2 trigger. Furthermore, at high CTAB concentrations (≥ 0.8 mM), a novel long-term stable conventional emulsion was obtained after the CS aggregates at the oil-water interface were entirely replaced by CTAB. Compared with other stimuli, CO2 is recognized as a green trigger that doesn't cause contaminations in the system, which has potential applications in organic synthesis and polymerization. Our strategy provides a simple and effective method to smartly control the properties of the emulsions (such as the emulsion type, stability, and viscosity), obtaining an intelligent emulsion to meet different requirements in many applications.

Comparative analysis of millet bran nanocelluloses with various morphologies: Revealing differences in the formation mechanism and structure characteristics

To investigate the differences of nanocelluloses with various morphologies, ammonium persulphate (APS) oxidation, H3PO4 dissolution and regeneration, and ball milling combined with 1-butyl-3-methylimidazolium chloride ([BMIM]Cl) as a medium were applied to isolate cellulose nanocrystals (MCNCs), cellulose nanospheres (MCNSs) and cellulose fibrils (MCNFs) from millet bran. The structure, properties, and formation mechanism of three nanocelluloses were comparatively investigated by Fourier transform infrared spectroscopy, X-ray diffraction, thermogravimetric analysis, atomic force microscope, scanning electronic microscope, and emulsifying ability evaluation. MCNCs had needle-like structures due to the removal of amorphous regions, MCNFs appeared fibrous structures due to swelling and mechanical force, and MCNSs displayed spherical structures through self-assembly. MCNCs and MCNFs were confirmed to exhibit cellulose I structures with crystallinities of 61.24 % and 50.09 %, respectively. MCNSs showed the highest crystallinity of 68.41 % with a cellulose II structure. MCNFs and MCNSs exhibited higher initial decomposition temperatures, while MCNCs showed the highest residual mass. MCNFs suspension showed the highest apparent viscosity, while MCNSs suspension demonstrated superior dispersion. MCNSs-emulsion displayed the smallest droplet size, and MCNFs-emulsion exhibited the highest viscosity. This study reveals the formation mechanisms and relationship between morphologies and properties of three millet bran nanocelluloses, providing a theoretical basis for their application.

Using kraft lignin nanoparticles for the stabilization of nano/micro wax carriers

Due to its amphiphilic structure, lignin has the potential to stabilize emulsions via adsorption at the oil/water interface. By converting lignin into nanoparticles, we can significantly enhance its emulsion-stabilizing capabilities through a Pickering-type stabilization mechanism. Two essential elements may be modified to fine-tune emulsion stability: the size of the lignin nanoparticles (LNPs) and the physicochemical nature of the lipid phase. In this context, we highlight the behavior and utility of unmodified LNPs in the preparation of Pickering emulsions made up of water and a complex bio-based pharmaceutical-grade wax that can be used for the formulation of lipid carriers. As a proof-of-concept, we employ the developed Pickering emulsions to encapsulate indocyanine green (ICG), an FDA-approved dye commonly used in medical imaging applications. We demonstrate that ultra-small LNPs are well-suited for the colloidal stabilization of pharmaceutical wax ester micro beads. This stabilization does not require any lignin modification. Additionally, we present evidence that our new lipid/lignin hybrid carrier has potential as a new drug delivery system.

Lignocellulosic biomass-derived functional nanocellulose for food-related applications: A review

In recent years, nanocellulose (NC) has gained significant attention due to its remarkable properties, such as adjustable surface chemistry, extraordinary biological properties, low toxicity and low density. This review summarizes the preparation of NC derived from lignocellulosic biomass (LCB), including cellulose nanofibrils (CNF), cellulose nanocrystals (CNC), and lignin-containing cellulose nanofibrils (LCNF). It focuses on examining the impact of non-cellulosic components such as lignin and hemicellulose on the functionality of NC. Additionally, various surface modification strategies of NC were discussed, including esterification, etherification and silylation. The review also emphasizes the progress of NC application in areas such as Pickering emulsions, food packaging materials, food additives, and hydrogels. Finally, the prospects for producing NC from LCB and its application in food-related fields are examined. This work aims to demonstrate the effective benefits of preparing NC from lignocellulosic biomass and its potential application in the food industry.

Enhancing cellulose-stabilized multiphase/Pickering emulsions systems: A molecular dynamics perspective

Cellulose stabilized multiphase systems (CSMS) have garnered significant attention due to their ultra-stabilization mechanism and vast potential across different fields. CSMS have found valuable applications in scientific disciplines, including Food Science, Pharmaceutical Science, Material Science, and related fields, owing to their beneficial attributes such as sustainability, safety, renewability, and non-toxicity. Furthermore, MPS exhibit novel characteristics that enable multiple mechanisms to produce HIPEs, aerogels, and oleogels revealing undiscovered information. Therefore, to explore the undiscovered phenomena of MPS, molecular level insights using advanced simulation/computational approaches are essential. The molecular dynamics simulation (MDS), play a valuable role in analyzing the interactions of ternary interphase. The MDS have successfully quantified the interactions of MPS by generating, visualizing, and analyzing trajectories. Through MDS, researchers have explored CSMS at the molecular level and advanced their applications in 3D printing, packaging, preparation, drug delivery, encapsulation, biosensors, electronic devices, biomaterials, and energy conservation. This review highlights the remarkable advancements in CSMS over the past five years, along with contributions of MDS in evaluating the relationships that dictate the functionality and properties of CSMS. By integrating experimental and computational methods, we underscore the potential to innovate and optimize these multiphase systems for groundbreaking applications.

Composite hydrogels assembled from food-grade biopolymers: Fabrication, properties, and applications

Biopolymer hydrogels have a broad range of applications as soft materials in a variety of commercial products, including foods, cosmetics, agrochemicals, personal care products, pharmaceuticals, and biomedical products. They consist of a network of entangled or crosslinked biopolymer molecules that traps relatively large quantities of water and provides semi-solid properties, like viscoelasticity or plasticity. Composite biopolymer hydrogels contain inclusions (fillers) to enhance their functional properties, including solid particles, liquid droplets, gas bubbles, nanofibers, or biological cells. These fillers vary in their composition, size, shape, rheology, and surface properties, which influences their impact on the rheological properties of the biopolymer hydrogels. In this article, the various types of biopolymers used to fabricate composite hydrogels are reviewed, with an emphasis on edible proteins and polysaccharides from sustainable sources, such as plants, algae, or microbial fermentation. The different kinds of gelling mechanism exhibited by these biopolymers are then discussed, including heat-, cold-, ion-, pH-, enzyme-, and pressure-set mechanisms. The different ways that biopolymer molecules can organize themselves in single and mixed biopolymer hydrogels are then highlighted, including polymeric, particulate, interpenetrating, phase-separated, and co-gelling systems. The impacts of incorporating fillers on the rheological properties of composite biopolymer hydrogels are then discussed, including mathematical models that have been developed to describe these effects. Finally, potential applications of composite biopolymer hydrogels are presented, including as delivery systems, packaging materials, artificial tissues, wound healing materials, meat analogs, filters, and adsorbents. The information provided in this article is intended to stimulate further research into the development and application of composite biopolymer hydrogels.

Interfacial Cooperative Assembly of Surfactants and Opposite Wettability Nanoparticles Stabilizes Water-in-Oil Emulsions at High Temperature

Pickering emulsions have promising applications in the development of unconventional oil and gas resources. However, the high-temperature environment of the reservoir is not conducive to the stabilization of Pickering emulsions. In addition, the preparation of Pickering emulsions under low-energy emulsification and low-concentration emulsifier conditions is a difficult challenge. Here, we report a high-temperature resistant water-in-paraffin oil Pickering emulsion, which is synergistically stabilized by polyglycerol ester (PGE) and nanoparticles with opposite wettability (lipophilic silica and hydrophilic alumina). This emulsion can be prepared under mild stirring (500 rpm) conditions and can be stable at 140 °C for at least 30 days. The synergistic effects of surfactant, silicon nanoparticles (MSNPs) with different wettability, and alumina nanoparticles (AONPs) on the stability of both emulsions and water-oil interfacial membranes were investigated through bottle experiments, cryogenic scanning electron microscopy (cryo-SEM), optical microscopy, fluorescence microscopy, etc. The results showed that both hydrophobic MSNPs and hydrophilic AONPs are adsorbed together at the water-oil interface to stabilize the W/O emulsion, which can be prepared by 500 rpm stirring. The stability of emulsions strongly depends on the wettability of MSNPs, and the MSNP with moderate hydrophobicity (for example, aqueous phase contact angle of 136°) makes the emulsion exhibit the highest stability against aggregation and settling at elevated temperatures. The emulsion stabilization mechanism was revealed in terms of the adsorption capacity of the surfactant by MSNPs, the adsorption morphology and desorption energy of nanoparticles at the water-oil interface adsorption layer, and emulsion rheology. These findings demonstrate a novel and simple strategy to prepare Pickering W/O emulsions with high-temperature stability at low shear strength.

Innovative ultrasonic emulsification of cinnamon essential oil pickering emulsion stabilized by rice straw-derived cellulose nanocrystals

For the first time, ultrasonic emulsification was studied for cinnamon essential oil (CEO) Pickering emulsion, stabilized by cellulose nanocrystal (CNC) from rice straw. Sonication proved to be an effective method for emulsifying CEO, creating small emulsion droplets around 700 nm in size, with an even dispersion characterized through a low polydispersity index. The biomass-derived CNC exhibits high encapsulation efficiency (> 95 %) with varying CEO concentration (5-25 vol%), creating droplets with negative surface charge with limited aggregation of emulsions. Optimization through the Box Behnken design using response surface methodology provides a model for the interaction and effects of variables towards the formulation. Optimal condition was concluded to be at 11.47 vol% CEO, 0.84 wt/vol% CNC and at 6 sonication cycles. The optimized Pickering emulsions retain the antimicrobial properties of CEO, with a large inhibition zone and low MIC value of around 0.048 vol% CEO. DPPH inhibition assay indicates that the emulsification process enhances the antioxidation properties of cinnamon essential oil, expressed through a lower IC50 of 0.90 vol% CEO, in comparison to pure essential oil at 1.33 vol% CEO. Overall, this research proposes a novel approach towards using nanocellulose as carriers for essential oil with potential in a large variety of applications.

Advances of protein-based emulsion gels as fat analogues: Systematic classification, formation mechanism, and food application

Fat plays a pivotal role in the appearance, flavor, texture, and palatability of food. However, excessive fat consumption poses a significant risk for chronic ailments such as obesity, hypercholesterolemia, and cardiovascular disease. Therefore, the development of green, healthy, and stable protein-based emulsion gel as an alternative to traditional fats represents a novel approach to designing low-fat food. This paper reviews the emulsification behavior of proteins from different sources to gain a comprehensive understanding of their potential in the development of emulsion gels with fat-analog properties. It further investigates the emulsifying potential of protein combined with diverse substances. Then, the mechanisms of protein-stabilized emulsion gels with fat-analog properties are discussed, mainly involving single proteins, proteins-polysaccharides, as well as proteins-polyphenols. Moreover, the potential applications of protein emulsion gels as fat analogues in the food industry are also encompassed. By combining natural proteins with other components such as polysaccharides, polyphenols, or biopolymers, it is possible to enhance the stability of the emulsion gels and improve its fat-analog texture properties. In addition to their advantages in protecting oil oxidation, limiting hydrogenated oil intake, and delivering bioactive substances, protein-based emulsion gels have potential in food 3D printing and the development of specialty fats for plant-based meat.

Novel Carboxymethyl Cellulose/Gelatin-Based Film Incorporated with Zein-Stabilized Lemon Essential Oil Pickering Emulsion for the Preservation of Cherries

In this study, a zein-stabilized lemon essential oil Pickering emulsion (ZLPE) was incorporated into a carboxymethyl cellulose/gelatin (CMC/GL) composite film to develop a bio-based packaging material with bioactive properties. The average droplet size of the ZLPE was measured at 3.62 ± 0.08 μm, with a zeta potential of -31.33 ± 0.32 mV, highlighting its excellent stability. The image results of confocal laser microscopy and scanning electron microscopy validated the uniform distribution of ZLPE in the film. The incorporation of ZLPE reduced the water solubility of films by 45.90% and decreased its water vapor permeability by 22.61%, thereby enhancing its hydrophobicity. Additionally, the ZLPE-loaded film improved mechanical properties, enhanced UV-blocking capabilities, and increased thermal stability. The introduction of ZLPE led to the antioxidant activity of the CMC/GL film increasing by six times the original level and endowed it with outstanding antibacterial properties. As a result, cherries packaged with the ZLPE film demonstrated superior preservation performance and extended shelf life in the preservation experiment, exhibiting the film's potential as a food packaging material.

Low gelatin concentration assisted cellulose nanocrystals stabilized high internal phase emulsion: The key role of interaction

Low concentrations of gelatin (0.02-0.20 wt%) were applied to regulate the surface and interface properties of CNC (0.50 wt%) by forming CNC/G complexes. As gelatin concentration increased from 0 to 0.20 wt%, the potential value of CNC/G gradually changed from -44.50 to -17.93 mV. Additionally, various gelatin concentrations led to micromorphology changes of CNC/G complexes, with the formation of particle interconnection at gelatin concentration of 0.10 wt%, followed by network structure and enhanced aggregation at gelatin concentration of 0.15 and 0.20 wt% respectively. The water contact angle (25.91°-80.23°) and interface adsorption capacity of CNC/G were improved due to hydrophobic group exposure of gelatin. When gelatin concentration exceeded 0.10 % at a fixed oil phase volume fraction (75 %), a high internal phase emulsion (HIPE) stabilized by CNC/G can be formed with a good storage stability. The rheological and microstructure results of HIPE confirmed that low gelatin concentration can assist CNC to form stable emulsion structure. Especially, the auxiliary stabilization mechanism of various gelatin concentration was different. CNC/G-0.10 % and CNC/G-0.15 % stabilized HIPE mainly depended on the enhanced interface adsorption and network structure, while CNC/G-0.20 % stabilized HIPE mainly relied on enhanced interface adsorption/accumulation due to weak electrostatic repulsion and aggregate granular morphology of CNC/G-0.20 %.

Self-Assembled Nanocarrier Delivery Systems for Bioactive Compounds

Although bioactive compounds (BCs) have many important functions, their applications are greatly limited due to their own defects. The development of nanocarriers (NCs) technology has gradually overcome the defects of BCs. NCs are equally important as BCs to some extent. Self-assembly (SA) methods to build NCs have many advantages than chemical methods, and SA has significant impact on the structure and function of NCs. However, the relationship among SA mechanism, structure, and function has not been given enough attention. Therefore, from the perspective of bottom-up building mechanism, the concept of SA-structure-function of NCs is emphasized to promote the development of SA-based NCs. First, the conditions and forces for occurring SA are introduced, and then the SA basis and molecular mechanism of protein, polysaccharide, and lipid are summarized. Then, varieties of the structures formed based on SA are introduced in detail. Finally, facing the defects of BCs and how to be well solved by NCs are also elaborated. This review attempts to describe the great significance of constructing artificial NCs to deliver BCs from the aspects of SA-structure-function, so as to promote the development of SA-based NCs and the wide application of BCs.

Current progress in functionalization of cellulose nanofibers (CNFs) for active food packaging

There is a growing interest in utilizing renewable biomass resources to manufacture environmentally friendly active food packaging, against the petroleum-based polymers. Cellulose nanofibers (CNFs) have received significant attention recently due to their sustainability, biodegradability, and widely available sources. CNFs are generally obtained through chemical or physical treatment, wherein the original surface chemistry and interfacial interactions can be changed if the functionalization process is applied. This review focuses on promising and sustainable methods of functionalization to broaden the potential uses of CNFs in active food packaging. Novel aspects, including functionalization before, during and after cellulose isolation, and functionalization during and after material processing are addressed. The CNF-involved structural construction including films, membranes, hydrogels, aerogels, foams, and microcapsules, is illustrated, which enables to explore the correlations between structure and performance in active food packaging. Additionally, the enhancement of CNFs on multiple properties of active food packaging are discussed, in which the interaction between active packaging systems and encapsulated food or the internal environment are highlighted. This review emphasizes novel approaches and emerging trends that have the potential to revolutionize the field, paving the way for advancements in the properties and applications of CNF-involved active food packaging.

Highly water-resistant paper via infiltration with polymeric microspheres from nanocellulose-stabilized plant oil-derived monomer

Sustainable strategies to improve the water resistance of cellulose paper are actively sought. In this work, polymeric microspheres (PMs), prepared through emulsion polymerization of cellulose nanofibers stabilized rubber seed oil-derived monomer, were investigated as coatings on corrugated medium paper (CMP). After infiltrating porous paper with PMs, the water-resistant corrugated papers (WRCPn) with enhanced mechanical properties were obtained. When 30 wt% PMs were introduced, WRCP30 turned out to be highly compacted with an increased water contact angle of 106.3° and a low water vapor transmission rate of 81 g/(m2 d) at 23 °C. Meanwhile, the tensile strength of WRCP30 increased to 22.2 MPa, a 4-fold increase from CMP. When tested in a well-hydrated state, 71% of its mechanical strength in the dry state was maintained. Even with a low content of 10 wt% PMs, WRCP10 also exhibited stable tensile strength and water wettability during the cyclic soaking-drying process. Thus, the plant oil based sustainable emulsion polymers provide a convenient route for enhancing the overall performance of cellulose paper.

β-Cyclodextrin based Pickering emulsions for α-tocopherol delivery: Antioxidation stability and bioaccessibility

β-Cyclodextrin (β-CD) Pickering emulsion and cinnamaldehyde/β-cyclodextrin (CIN/β-CD) Pickering emulsion were prepared and the influences of oxidation and digestion were investigated. CIN/β-CD composite was better dispersed at the oil-water interface than β-CD. Hydrophobic group of CIN anchored in the oil phase and Hydrophilic hydroxyl group of β-CD extended into the aqueous phase, which allowed CIN/β-CD composite to be oriented at the oil-water interface and formed a more stable oil-water interface layer. β-CD Pickering emulsion was more susceptible to oxidative deterioration than CIN/β-CD Pickering emulsion, its malondialdehyde (MDA) value was as high as 509.41 ± 9.37 nmol/L. Digestion experiment indicated that CIN/β-CD Pickering emulsion was released inner oil phase in the small intestine and free fatty acid (FFA) release rate was 44.32 ± 1.08%. Pharmacokinetic parameters manifested that α-tocopherol peak concentration (Cmax) was 64.32 ± 6.45 mg/L and the peak time (Tmax) appeared at 5 h after administration of CIN/β-CD Pickering emulsion.

Effect of TEMPO-oxidized bacterial cellulose nanofibers stabilized Pickering emulsion of cinnamon essential oil on structure and properties of gelatin composite films

Pure gelatin film often exhibits high hydrophilicity and a lack of antibacterial activity, hindering its practical application in the field of food preservation. To address these issues, we incorporated 2,2,6,6-tetramethylpiperidine-1-oxyl radical (TEMPO)-oxidized bacterial cellulose (TOBC) nanofibers stabilized cinnamon essential oil (CEO) Pickering emulsions into the gelatin matrix to develop active food packaging films. The study revealed that the good distribution of emulsion droplets in the film matrix. While with increasing Pickering emulsion proportion, the microstructures of composite films were more heterogeneous, showing some pores or cavities. In addition, the insertion of TOBC-stabilized CEO emulsions could improve the elongation at break (EAB), water-resistance, UV blocking ability, and antibacterial activity of film, but reduced its tensile strength (TS) and water vapor barrier properties (WVP). Notably, the film prepared with 4 % TOBC-stabilized CEO Pickering emulsion demonstrated enhanced preservation of strawberries. Overall, the as-prepared gelatin-based active composite films have considerable potential for food packaging.

Process design for acidic and alcohol based deep eutectic solvent pretreatment and high pressure homogenization of palm bunches for nanocellulose production

This research aimed to study on nanocellulose production from palm bunch using process design and cost analysis. Choline chloride based deep eutectic solvent pretreatment was selected for high-purity cellulose separation at mild condition, followed by nano-fibrillation using mechanical treatment. Three types of choline chloride-based deep eutectic solvents employing different hydrogen-bond donors (HBDs) namely lactic acid, 1,3-butanediol and oxalic acid were studied. The optimal cellulose extraction condition was choline chloride/lactic acid (ChLa80C) pretreatment of palm empty bunch at 80 °C followed by bleaching yielding 94.96%w/w cellulose content in product. Size reduction using ultrasonication and high-pressure homogenization produced nanocellulose at 67.12%w/w based on cellulose in raw material. Different morphologies of nanocellulose were tunable in the forms of nanocrystals, nano-rods and nanofibers by using dissimilar deep eutectic solvents. This work offered a sustainable and environmentally friendly process as well as provided analysis of DES pretreatment and overview operating cost for nanocellulose production. Application of nanocellulose for the fabrication of highly functional and biodegradable material for nanomedicine, electronic, optical, and micromechanical devices is achievable in the near future.