Responsive Emulsion Gels with Tunable Properties Formed by Self-Assembled Nanofibrils of Natural Saponin Glycyrrhizic Acid for Oil Structuring

Food-grade emulsion gels and oleogels prepared by all-natural dual nanofibril system from citrus fiber and glycyrrhizic acid

The natural dual nanofibril system consisting of the rigid semicrystalline nanofibrils disintegrated from citrus fiber (CF) and soft semiflexible nanofibrils self-assembled from glycyrrhizic acid (GA) has been recently shown to be effective structural building blocks for fabrication of emulsion gels. In this work, the effect of the CF nanofibrils prepared by different mechanical disintegration approaches (i.e., high-pressure microfluidization and hydrodynamic cavitation) on the interfibrillar CF-GA interactions and the subsequent formation and properties of emulsion gels were investigated, with the aim of evaluating the potential of the dual nanofibril-stabilized emulsion gels as templates for synthesizing all-natural edible oleogels. The obtained results demonstrate that compared to the cavitation, the high-pressure microfluidization is more capable of generating CF nanofibrils with a higher degree of nanofibrillation and individualization, thus forming a denser CF-GA gel network with higher viscoelasticity and structural stability due to the stronger multiple intrafibrillar and interfibrillar interactions. The emulsion gels stabilized by the dual nanofibril system are demonstrated to be an efficient template to fabricate solid-like oleogels, and the structural properties of the oleogels can be well tuned by the mechanical disintegration of CF and the GA nanofibril concentration. The prepared oleogels possess high oil loading capacity, dense network microstructure, superior rheological and large deformation compression performances, and satisfactory thermal stability, which is attributed to the compact and ordered CF-GA dual nanofibrillar network via multiple hydrogen-bonding interactions in the continuous phase as well as at the droplet surface. This study highlights the unique use of all-natural dual nanofibrils to develop oil structured soft materials for sustainable applications.

Cholic Acid/Glutathione-Assembled Nanofibrils for Stabilizing Pickering Emulsion Biogels

Achieving the delicate balance required for both emulsion and gel characteristics, while also imparting biological functionality in gelled emulsions, poses a significant challenge. Herein, Pickering emulsion biogels stabilized is reported by novel biological nanofibrils assembled from natural glutathione (GSH) and a tripod cholic acid derivative (TCA) via electrostatic interactions. GSH, composed of tripeptides with carboxyl groups, facilitates the protonation and dissolution of TCA compounds in water and the electrostatic interactions between GSH and TCA trigger nanofibrillar assembly. Fibrous nuclei initially emerge, and the formed mature nanofibrils can generate a stable hydrogel at a low solid concentration. These nanofibrils exhibit efficient emulsifying capability, enabling the preparation of stable Pickering oil-in-water (O/W) emulsion gels with adjustable phase volume ratios. The entangled nanofibrils adsorbed at the oil-water interface restrict droplet movement, imparting viscoelasticity and injectability to the emulsions. Remarkably, the biocompatible nanofibrils and stabilized emulsion gels demonstrate promising scavenging properties against reactive oxygen species (ROS). This strategy may open new scenarios for the design of advanced emulsion gel materials using natural precursors and affordable building blocks for biomedical applications.

Bioactive foamulsion gels: a unique structure prepared with gellan gum and Acanthophyllum glandulosum extract

BACKGROUND

Foamulsions have become increasingly popular in the food industry due to their ability to enhance the textural, sensory and health-promoting properties of food products. This study was therefore aimed to design and prepare a novel gelled structure, foamulsion gel containing 0-600 g L-1 oil, with gellan gum (GG; 7, 10 and 13 g L-1) and saponin-rich antioxidant Acanthophyllum glandulosum extract (AGE; 2, 6 and 10 g L-1).

RESULTS

The interaction between components was confirmed by infrared spectroscopy. The overrun and porosity of the foamulsion gels increased with antioxidant AGE (1.30 times) and reduced with oil (up to ca 70% and 30%, respectively) and GG levels. The systems were highly stable, and no water or oil was released during the physical stability experiments. Microscopic images showed that the size of air cells was significantly larger than that of oil droplets. The foamulsion gels based on 13 g L-1 GG and 10 g L-1 AGE had markedly higher elastic (G') and viscous (G'') moduli than other samples, and exhibited an elastic and solid-like behavior (G' > G''). The highest gel firmness was found in oil-free sample, and the presence of oil resulted in a lower firmness induced by the larger size and lubrication effect of oil droplets.

CONCLUSION

As a result, the interactions between AGE, GG and oil could lead to the creation of new aerated structures known as bioactive foamulsion gels. These gels exhibit excellent foamability, stability and viscoelasticity and may find applications in the development of novel, healthy and low-calorie aerated foods. © 2024 Society of Chemical Industry.

Interfacial assembly and rheology of multi-responsive glycyrrhizic acid at liquid interfaces

Glycyrrhizic acid (GA), a naturally derived food-grade saponin molecule, is a promising alternative to synthetic surfactants for stabilizing multiphase systems including emulsions and foams, due to its biological activity and surface-active properties. Understanding the interfacial behavior of GA, particularly in relation to its complex self-assembly behaviors in water induced by multiple environmental stimuli, is crucial to its application in multiphase systems. In this study, we comprehensively investigate the interfacial structure and rheological properties of GA systems, as a function of pH and temperature, through Langmuir-Blodgett films combined with atomic force microscopy, interfacial particle tracking, adsorption kinetics, stress-relaxation behavior and interfacial dilatational rheology. The variation of solution pH provokes pronounced changes in the interfacial properties of GA. At pH 2 and 4, GA fibril aggregates/fibrils adsorb rapidly, followed by rearrangement into large lamellar and rod-like structures, forming a loose and heterogeneous fibrous network at the interface, which exhibit a stretchable gel-like behavior. In contrast, GA at pH 6 and 8, featuring micelles or monomers in solutions, adsorb slowly to the interface and re-assemble partially into small micelle-like or irregular structures, which lead to a dense and homogeneous interfacial layer with stiffer glassy-like responses. With successively elevated temperature, the GA structures (pH 4) at the interface break into smaller fragments and further adsorption is promoted. Upon cooling, the interfacial tension of GA further decreases and a highly elastic interfacial layer may be formed. The diverse GA assemblies in bulk solution impart them with rich and intriguing interfacial behaviors, which may provide valuable mechanistic insights for the development of novel edible soft matter stabilized by GA.

Glycyrrhizic acid aggregates seen from a synthetic surfactant perspective

Bio- or plant-based surfactants are a sustainable and renewable alternative to replace synthetic chemicals for environmental, drugs and food applications. However, these "green" surfactants have unique molecular structures, and their self-assembly in water might lead to complex morphologies and unexpected properties. The micellization of saponin molecules, such as glycyrrhizic acid (GA), differs significantly from those of conventional synthetic surfactants, yet these differences are often overlooked. Saponins self-assemble in complex hierarchical helical morphologies similar to bile salts, rather than the expected globular, ellipsoidal and wormlike micelles. Here, we review two potential routes for molecular self-assembly of GA, namely kinetics of crystallization and thermodynamic equilibrium, focusing on their structure as a function of concentration. Some uncertainty remains to define which route is followed by GA self-assembly, as well as the first type of aggregate formed at low concentrations, thus we review the state-of-the-art information about GA assembly. We compare the self-assembly of GA with conventional linear surfactants, and identify their key similarities and differences, from molecular and chemical perspectives, based on the critical packing parameter (CPP) theory. We expect that this work will provide perspectives for the unclear process of GA assembly, and highlight its differences from conventional micellization.

Tailoring the oral sensation and digestive behavior of konjac glucomannan-gelatin binary hydrogel based bigel: Effects of composition and ratio

In the food industry, there is a growing demand for bigels that offer both adaptable oral sensations and versatile delivery properties. Herein, we developed bigels using a binary hydrogel of konjac glucomannan (KGM) and gelatin (G) combined with a stearic acid oleogel. We closely examined how the oleogel/hydrogel volume ratio (φ) and the KGM/G mass ratio (γ) influenced various characteristics of the bigels, including their microstructure, texture, rheological properties, thermal-sensitivity, oral tribology, digestive stability, and nutraceutical delivery efficiency. A noteworthy observation was the structural evolution of the bigels with increasing φ values: transitioning from oleogel-in-hydrogel to a bicontinuous structure, and eventually to hydrogel-in-oleogel. Lower γ values yielded a softer, thermally-responsive bigel, whereas higher γ values imparted enhanced viscosity, stickiness, and spreadability to the bigel. Oral tribology assessments demonstrated that φ primarily influenced the friction sensations at lower chewing intensities. In contrast, γ played a significant role in augmenting oral friction perceptions during more intense chewing. Additionally, φ dictated the controlled release and bioaccessibility of curcumin, while γ determined digestive stability. This study provides valuable insights, emphasizing that through meticulous selection and adjustment of the hydrogel matrix composition, bigels can be custom-fabricated to achieve specific oral sensations and regulated digestive behaviors.

Development of antibacterial nanocomposites by combination of bacterial cellulose/chitin nanofibrils and all-natural bioactive nanoparticles

In this study, a functional composite membrane was facilely fabricated by using a dual nanofibril system of bacterial cellulose (BC) and chitin (CH) nanofibrils as bio-based building blocks. The BC-CH membranes with enhanced antibacterial activity were constructed by incorporation of all-natural bioactive nanoparticles (GBTPs), which were formed by spontaneous molecular interactions of three naturally occurring active small molecules, i.e., glycyrrhizic acid (GA), berberine (BR), and tannic acid (TA). The microstructure, physicochemical properties, and antibacterial behaviors of the resulting BC-CH-GBTPs nanocomposites were then characterized. The obtained results showed that the GBTPs with a diameter of around 50-100 nm and membrane matrix were bound by non-covalent interactions, and the addition of GBTPs did not compromise the structural integrity and thermal stability of the composites, which retained good mechanical properties. Furthermore, the addition of GBTPs led to a rougher surface structure and increased the water contact angle of the membrane surfaces from 48.13° to 59.80°. The antimicrobial tests indicate that the BC-CH-GBTPs nanocomposites exhibited significant inhibitory effects against Escherichia coli and Staphylococcus aureus, showing a satisfactory antibacterial ability. These results suggest that the BC-CH-GBTPs nanocomposites based on all-natural, plant-based building blocks, hold promising potentials as active packaging materials for sustainable applications.

Oral sensation and gastrointestinal digestive profiles of bigels tuned by the mass ratio of konjac glucomannan to gelatin in the binary hydrogel matrix

Bigels with tunable oral sensation and controlled gastrointestinal digestive profiles are highly demanded in the food industry. A binary hydrogel consisting of different mass ratio of konjac glucomannan to gelatin (φ) was designed to fabricate bigels with stearic acid oleogel. The impacts of φ on the structural, rheological, tribological, flavor release, and delivery properties of bigels were investigated. Structural transition of bigels from hydrogel-in-oleogel to bi-continuous, and then to oleogel-in-hydrogel type, as φ increased from 0.6 to 0.8, and then to 1.0-1.2. Enhanced storage modulus and yield stress were achieved along with the increased φ, while the structure-recovery properties of bigel decreased with increased φ. Under all the tested φ, the viscoelastic modulus and viscosity decreased significantly at oral temperatures but maintained the gel state, and the friction coefficient increased along with the increased φ under high chewing degree. Flexible control over the swelling, the lipid digestion and the release of lipophilic cargos were also observed, with the total release of free fatty acids and quercetin significantly reduced with the increased φ. This study presents a novel manipulation strategy to control oral sensation and gastrointestinal digestive profiles of bigels via tuning the fraction of konjac glucomannan in the binary hydrogel.

Construction of interfacial crystallized oleogel emulsion with improved thermal stability

In this study, we reported a facile strategy to produce an interfacial crystallized oleogel emulsion for improved thermal stability. The interfacial crystallization of ceramide (non-interfacial active oleogelator) was achieved by addition of a surface active compound, which was demonstrated by interfacial rheology tests and polarized light microscopy. For successfully prepared interfacial crystallized emulsions, smaller particle size was observed when the gelator concentration was lower. However, better thermal stability was achieved when oleogelator concentration was higher than 1 wt%. Results from differential scanning calorimetry, X-ray diffraction and Fourier transform infrared spectroscopy suggested that the interfacial adsorption of ceramide was due to its co-crystallization with the emulsifier driven by hydrogen bonds formed by multiple sites. It provided appropriate crystallinity and steric repulsion for oleogel emulsions against oil droplet coalescence during heating process. This strategy greatly enriches oleogel emulsion formulations and their potential applications in food products involved with thermal treatment.

Self-assembled glycyrrhetinic acid derivatives for functional applications: a review

Glycyrrhetinic acid (GA), a famous natural product, has been attracting more attention recently because of its remarkable biological activity, natural sweetness, and good biocompatibility. In the past few years, a considerable amount of literature has grown up around the theme of GA-based chemical modification to broaden its functional applications. Promising structures including gels, micelles, nanoparticles, liposomes, and so forth have been constantly reported. On the one hand, the assembly mechanisms of various materials based on GA derivatives have been elucidated via modern analytical techniques. On the other hand, their potential application prospects in edible additives, intelligent drug delivery, and other fields have been investigated fully due to availability, biocompatibility, and controllable degradability. Inspired by these findings, a systematic summary and classification of the materials formed by GA derivatives seems necessary and meaningful. This review sums up the new functional applications of GA derivatives for the first time and provides better prospects for their application and development.

Edible pentacyclic triterpenes: A review of their sources, bioactivities, bioavailability, self-assembly behavior, and emerging applications as functional delivery vehicles

Edible pentacyclic triterpenes (PTs) are a group of nutraceutical ingredients commonly distributed in human diets. Existing evidence has proven that they have various biological functions, including anticancer, antioxidant, anti-inflammatory and hypoglycemic activities, making them as "functional factor" for a long time. However, their properties of strong hydrophobicity, poor permeability, poor absorption, and rapid metabolism result in low oral bioavailability, which dramatically hinders their efficacy for use. Recently, free PTs have successively been found to self-assemble or co-assemble into self-contained nanostructures with enhanced water dispersibility and oral bioavailability, which seems to be an efficient processing method for increased oral efficacy. Of particular interest, formulating them into nanostructures can also be introduced as functional delivery carriers for bioactive compounds or drugs with various advantages, such as improved stability, controlled release, enhanced oral bioavailability, synergistic bioactivity, and targeted delivery. This review systematically summarized the chemical structures, plant sources, bioactivities, absorption, metabolism, and oral bioavailability of PTs. Notably, we emphasized their self-assembly properties and emerging role as functional delivery carriers for nutrients, suggesting that PT nanostructures are not only efficient oral forms when introduced into foods but also functional delivery materials for nutrients to expand their commercial food applications.

Thermoresponsive Dual-Structured Gel Emulsions Stabilized by Glycyrrhizic Acid Nanofibrils in Combination with Monoglyceride Crystals

Responsive dual-structured emulsions and gel emulsions have attracted more and more attention due to their complex microstructures, on-demand responsive properties, and controlled release of active cargoes. In this work, the effect of monoglyceride (MG)-based oil phase structuring on the formation and stability, structural properties, and thermoresponsive and cargo release behavior of gel emulsions stabilized by glycyrrhizic acid (GA) nanofibrils were investigated. Owing to the formation of GA fibrillar networks in the aqueous phase and MG crystalline networks in the oil phase, a stable dual-structured gel emulsion can be successfully developed. The microstructure of the dual-structured gel emulsions largely depended on the concentration of MG in the oil phase. At low MG concentrations (1-2 wt%), the larger formed and lamellar MG crystals may pierce the interfacial fibrillar film, inducing the formation of partially coalesced droplets. In contrast, at high MG concentrations (4 wt% or above), the smaller MG crystals with enhanced interfacial activity can lead to the formation of a bilayer shell of GA nanofibrils and MG crystals, thus efficiently inhibiting the interfacial film damage and forming a jamming structure with homogeneously distributed small droplets. Compared to pure GA nanofibril gel emulsions, the GA-MG dual-structured gel emulsions showed significantly improved mechanical performance as well as good thermoresponsive behavior. Moreover, these stable GA-MG gel emulsions can be used as food-grade delivery vehicles for encapsulating and protecting hydrophobic and hydrophilic bioactive cargoes. They also have great potential as novel and efficient aroma delivery systems showing highly controlled volatile release. The dual-structured emulsion strategy is expected to broaden the applications of natural saponin GA-based gel emulsions in the food, pharmaceutical, and personal care industries.

Effects of Polysaccharide Concentrations on the Formation and Physical Properties of Emulsion-Templated Oleogels

An emulsion template method was an effective way to prepare oleogels. However, there were few reports on how hydroxypropyl methylcellulose-pectin (HPMC-PC) mixtures affected the physicochemical properties of the obtained oleogels. In this study, the oleogels were prepared by an emulsion template method. The influences of HPMC and PC concentrations on the formation and physical properties of the emulsions and oleogels were investigated, by analyzing particle size distribution, microstructure, rheological test, oil loss, and crystallinity. The results of particle sizes and microstructure showed that a high concentration of HPMC and PC exhibited a better emulsification performance. The rheological tests indicated that a high concentration of HPMC and PC contributed to an increase in the mechanical strength of emulsions and oleogels. Moreover, an increase in an HPMC and PC concentration was beneficial to reduce the oil loss of oleogels. However, the change of HPMC and PC concentrations had no significant effect on the X-ray diffraction pattern of oleogels. This study could provide a theoretical basis for the construction of polysaccharide-based oleogels.

Systematic comparison of structural and lipid oxidation in oil-in-water and water-in-oil biphasic emulgels: effect of emulsion type, oil-phase composition, and oil fraction

BACKGROUND

Because many common foods are emulsions (mayonnaise, margarine, salad dressing, etc.), a better understanding of lipid oxidation is crucial for the formulation, production, and storage of the relevant consumer products. We prepared oil-in-water (O/W) and water-in-oil (W/O) emulgels, and their architecture was characterized before monitoring lipid oxidation under thermally accelerated conditions to systematically compare the effect of emulsion type, oil composition, and oil fraction on the structure and lipid oxidation in thee biphasic emulgel systems.

RESULTS

Higher susceptibility of lipids to oxidation (>2.5 times) was observed in the biphasic O/W and W/O emulgels than in soybean oil owing to an interfacial region. In the heterogeneous emulsion systems, W/O emulgels had oxidation resistance than O/W emulgels did. Compared with the oil-phase composition of high oleic sunflower, soybean, and flaxseed oils, oxidation sensitivity of emulsified lipids was significantly raised as the degree of unsaturation increased from 100.72 to 203.07. Moreover, increasing oil fraction from 75% to 85% led to an obvious increase in total oxidation in O/W emulgels but a decrease in W/O emulgels. In addition to emulsion size and oil unsaturation, viscoelasticity had a remarkable effect on the low-unsaturated oil oxidation (e.g. high oleic sunflower oil).

CONCLUSION

Physical and structural phenomena played important roles in lipid oxidation based on a mass transport principle. These findings provide novel information for designing the structures of emulsion gels for controlling lipid oxidation through the cooperation of both formulation and architecture principles. © 2022 Society of Chemical Industry.

Fabrication and characterization of Pickering high internal phase emulsions stabilized by debranched starch-capric acid complex nanoparticles

High internal phase emulsions (HIPEs) stabilized by debranched starch-capric acid (DBS-CA) complex nanoparticles were fabricated and their performance was evaluated. DBS-CA was prepared through enzymatic debranching and solid encapsulation methods, and displayed V-type crystalline structure. Contact angle measurements show enhanced hydrophobicity of DBS-CA compared to native starch. The DBS-CA nanoparticles have an average size of 463.77 nm and tended to be aggregating as analyzed by scanning electron microscope and dynamic light scattering particle size analysis. When used as a particulate emulsifier, DBS-CA could stabilize HIPEs with oil volume fraction as high as 80%. The HIPEs showed pH-dependent properties; good storage stability and mechanical strength were achieved within pH range from 3 to 11, especially under alkaline conditions. It was proposed that smaller particle size and higher surface charging were responsible for the more tightly connected gel structure and thus their performance. This study demonstrates a novel approach to fabricate food-grade Pickering HIPEs, which may have many promising potential applications in the food industry.

Robust and highly adaptable high internal phase gel emulsions stabilized solely by a natural saponin hydrogelator glycyrrhizic acid

Herein, we report a new class of high internal phase gel emulsions (gel-HIPEs) that are mechanically robust, adaptable, and processable. They can be synthesized facilely by using the natural food-grade saponin glycyrrhizic acid (GA) as the sole stabilizer, which is shown to be versatile for various oils. The structural properties of these HIPEs including appearance, viscoelasticity and processability are well controlled by simply changing the concentration of GA nanofibrils. When the GA nanofibril concentration exceeds 0.3 wt%, the unique gel-HIPEs can be produced through the formation of fibrillar hydrogel networks in the continuous phase. When the nanofibril concentration only increases to 5 wt%, it is surprising to see that these gel-HIPEs display an extremely high mechanical strength, and the storage moduli as well as the yield stress values can reach 408.5 kPa and 3340 Pa (or even more), respectively. We conjecture that such remarkable mechanical performance is mainly attributed to the highly viscoelastic GA nanofibrillar networks in the continuous phase of gel-HIPEs, which can actively trap the nanofibril-coated emulsion droplets and thus strengthen the gel matrix. Consequently, the robust gel-HIPEs can be used as a solid template to fabricate stable porous materials without the need for crosslinking of the continuous phase, and the open- and closed-cell foam microstructures are controlled by the nanofibril concentration. Furthermore, the nanofibril-based HIPEs are promising long-term delivery vehicles with controlled-release properties for lipophilic active cargoes, since the strong fibrillar networks at the droplet surfaces and in the continuous phase can effectively retard the active release.

Tailoring structure and properties of long-lived emulsion foams stabilized by a natural saponin glycyrrhizic acid: Role of oil phase

Novel supramolecular nanofibrils assembled from food-grade saponin glycyrrhizic acid (GA) are effective building blocks to make complex multiphase systems, e.g., emulsion foams. In this work, the effects of different oil phases (castor oil, sunflower oil, dodecane, and limonene) on the formation, stability and structural properties of long-lived emulsion foams prepared by GA nanofibrils (GNs) were investigated. The obtained results showed that soft-solid emulsion foams (4 wt% GNs) can be fabricated, independently of oil phase, and their structural properties, viscoelasticity, and tribological properties can be well tuned by oil phase polarity. Compared to the GNs aqueous foams, the presence of jammed emulsion droplets in the liquid channels and at the surfaces of bubbles can provide a higher bubble stability for emulsion foams. For more polar oil phase (castor oil), GNs showed a higher affinity to the oil-water interface with a lower interfacial tension, thus forming smaller oil droplets and bubbles, which leads to the higher mechanical strength, denser network microstructures, and lower friction coefficients of emulsion foams. However, the limonene foam exhibited weak storage stability and rheological properties, as well as the relatively low lubrication, which may be related to the formation of oil droplet aggregates and clusters induced by the volatility of limonene. GN-based emulsion foams are thermoresponsive, independently of oils, and the temperature-switchable process for the destabilization and regeneration of foams can be controlled and repeated. These emulsion foams based on natural saponin nanofibrils with tunable properties have potential sustainable applications in foods, pharmaceuticals, and personal care products.

One-pot ultrasonic cavitational emulsification of phytosterols oleogel-based flavor emulsions and oil powder stabilized by natural saponin

Phytosterols oleogel-based flavor emulsions were successfully fabricated for the first time using natural tea saponin as emulsifier and one-pot ultrasonic technique. The effects of ultrasonic time and power, surfactant concentration, and type of flavor oils (e.g., orange, lemon and peppermint) on the emulsion droplet size were investigated. Submicron emulsions with a dispersed phase made by flavor oil (20 wt%) + phytosterol (4 wt%) were stabilized with 3 wt% saponin were obtained by applying an ultrasonic time of 5 min and ultrasonic power of 280 W. The natural tea saponin emulsions exhibited a superior stability and encapsulation efficiency of phytosterol, compared to traditional emulsifiers. Flavor oil-phytosterol enriched powders were prepared by spray-drying and characterized by SEM, XRD and repose angle. The natural saponin encapsulated oil + phytosterol powders had excellent fluidity, redispersion behavior and low phytosterol crystallinity. It was demonstrated that ultrasound is an effective and suitable technique for fabricating fortified flavor emulsions and microcapsules, which may be used for developing functional lipids-based applications in the food, beverage and cosmetic industries.

pH-Responsive Pickering high internal phase emulsions stabilized by Waterborne polyurethane

HYPOTHESIS

Waterborne polyurethane (WPU) is a common colloidal dispersion that can aggregate in the aqueous phase to form nanoparticles with hydrophobic polyurethane chains as the core and hydrophilic ionic groups as the shell. Considering their structure and pH-responsive functional groups, WPU nanoparticles could be ideal particulate emulsifiers for preparing pH-responsive Pickering high internal phase emulsions (HIPEs).

EXPERIMENTS

A series of anionic WPU with different content of 2,2-bis(hydroxymethyl)propionic acid (DMPA) side chains were synthesized via a polyaddition reaction. The DMPA content, size, ζ-potential, and interfacial behaviors of WPU were then investigated. Furthermore, the effects of particle concentration, internal phase fraction (ϕ), oil type, and pH values on the Pickering HIPEs' morphology, stability, and rheological behaviors were systematically studied. Finally, we demonstrated the emulsification-demulsification process of WPU-stabilized Pickering HIPEs and discussed its mechanism.

FINDINGS

Oil-in-water (O/W) Pickering HIPEs with tailored morphology and excellent pH-responsiveness were prepared from anionic WPU nanoparticles. The WPU concentration, ϕ, and oil type had a large impact on the formation and mean droplet size of the WPU-stabilized emulsions. Rheology analysis demonstrated that the strictly limited movement of droplets endowed the WPU-stabilized HIPEs with high stability, shear sensitivity, and excellent thixotropic recovery. By simply changing the aqueous-phase pH value, the WPU-stabilized HIPEs could undergo more than ten emulsification-demulsification cycles, as the physical and interfacial properties of WPU nanoparticles were pH-dependent. The excellent performance of the WPU-stabilized pH-responsive Pickering HIPEs exhibited their potential practical applications, such as for oil transportation and recovery, emulsion polymerization, and heterogeneous catalysis.

A hierarchical emulsion system stabilized by soyasaponin emulsion droplets

Oil/water (O/W) emulsion droplets coated with soyasaponin (Ssa) were used as emulsifiers to prepare emulsions with hierarchical configurations (2.82 μm). Ssa is a natural triterpenoid with amphiphilic properties and an excellent emulsifying activity. Stable O/W emulsions were prepared and characterized using an ultrasonic method at a Ssa concentration of 2.5 wt%. The resultant hierarchical emulsions were further prepared using O/W droplets as emulsifiers. It was observed that the stability of the hierarchical emulsions changed with alterations to the ratio of O/W droplets to the oil phase. As the number of droplets increased, the more the surface area of the hierarchical emulsion was covered. Additional observations included a decreased particle size, increased negative charge and viscoelastic behavior, and enhanced emulsion stability. The emulsion was most stable when the O/W droplet addition was 29%. The addition of O/W droplets continued to increase, and there was an imbalance in the ratio of O/W droplets to the oil phase; the excess O/W droplets induced instability in the emulsion, resulting in a degradation of the emulsion quality. We monitored hierarchical emulsions with different concentrations of emulsifiers for 30 days, and the results indicated that hierarchical emulsions could meet the demand for long-term storage. This provides a new theoretical basis for the construction and application of complex emulsion systems.

Recent Advances and Applications of Plant-Based Bioactive Saponins in Colloidal Multiphase Food Systems

The naturally occurring saponins exhibit remarkable interfacial activity and also possess many biological activities linking to human health benefits, which make them particularly attractive as bifunctional building blocks for formulation of colloidal multiphase food systems. This review focuses on two commonly used food-grade saponins, Quillaja saponins (QS) and glycyrrhizic acid (GA), with the aim of clarifying the relationship between the structural features of saponin molecules and their subsequent self-assembly and interfacial properties. The recent applications of these two saponins in various colloidal multiphase systems, including liquid emulsions, gel emulsions, aqueous foams and complex emulsion foams, are then discussed. A particular emphasis is on the unique use of GA and GA nanofibrils as sole stabilizers for fabricating various multiphase food systems with many advanced qualities including simplicity, ultrastability, stimulability, structural viscoelasticity and processability. These natural saponin and saponin-based colloids are expected to be used as sustainable, plant-based ingredients for designing future foods, cosmetics and pharmaceuticals.

Bioinspired organohydrogels with heterostructures: Fabrications, performances, and applications

Since emerging in 1960, the artificial hydrogels have garnered enormous attentions in scientific community due to their high level of similarities to biological soft tissues in both structures and properties. With the proceeding of research, the concern of hydrogels is gradually shifted from fundamental investigation to abundant functionalization. In contrast to the natural soft tissues, the current artificial hydrogels still possess relatively simple structures and unsatisfactory environmental adaptability, extremely limiting their practical applications in complex environments. Enlightened by the prominent adaptability of biological organisms, the binary cooperative complementary principle is utilized to develop bioinspired organohydrogels by combining two components with opposite but cooperative physiochemical features. The present review provides the advanced progresses of bioinspired organohydrogels with sophisticated heterogeneous networks and desirably environmental adaptabilities. We clearly summarize the synthesizing strategies in regard to both corresponding mechanisms and typical examples, including macroscopic organohydrogels, organohydrogels with binary solvent, organohydrogels with heteronetworks, and emulsion-based organohydrogels. Meanwhile, the intriguing features of the reported organohydrogels, such as temperature resistance, switchable mechanics, adaptive wettability, and opposite components compatibility, are also clearly highlighted with a short overview of their promising applications. Ultimately, the current challenges and perspectives on the future development of bioinspired organohydrogels are also discussed.

Solid encapsulation of lauric acid into "empty" V-type starch: Structural characteristics and emulsifying properties

Lauric acid was introduced into "Empty" V-type starch using a solid encapsulation method. The structural characteristics and emulsifying properties of the starch-fatty acid complex (SFAC) were explored as a function of the complexing temperature. X-ray diffraction and differential scanning calorimetry confirmed that SFAC was mainly composed of type-I amylose inclusion complexes. Contact angle measurements revealed that the hydrophobic properties of SFAC were closely related to the temperature-regulated complex index. The particle size range of SFAC gradually increased as the complexing temperature increased. The SFAC-stabilized Pickering emulsion at c of 5% and Φ of 40-60% possessed a small droplet size and long-term storage stability for up to 30 days, resulting from the formation of a gel-like network. This study provides new insight into the design of hydrophobic modified starch as a novel and multifunctional emulsifier and is of great help in the development of starch-based Pickering emulsion gels.

Large amplitude oscillatory shear (LAOS) for nonlinear rheological behavior of heterogeneous emulsion gels made from natural supramolecular gelators

The linear and nonlinear rheological behaviors of heterogeneous emulsions gels made from natural glycyrrhizic acid (GA) nanofibrils and sitosterol-oryzanol mixtures (sterols) were investigated using small amplitude oscillatory shear (SAOS) and large amplitude oscillatory shear (LAOS). The nonlinear rheological response was qualitatively analyzed using normalized Lissajous-Bowditch curves. The microstructure of the emulsion gels strongly depended on the concentration of sterols in the oil phase, and showed a percolated segregated network at 10-20 wt% sterols due to the partial coalescence of droplets, and a jamming transition without coalescence at higher sterols concentration of 30 wt%. The microstructure differences led to different linear and nonlinear viscoelastic behaviors of these emulsion gels. SAOS tests showed that the oil phase structuring by the sterols significantly enhance the viscoelasticity of GA nanofibril emulsion gels, and the percolating emulsion gels exhibited higher elasticity than the jammed emulsion gel, as evidenced by a lower damping factor and frequency power-law exponent. The data of crossover strain, phase angle, and the normalized Lissajous-Bowditch curves from LAOS tests further revealed that compared to the samples in a jammed state or without oil phase structuring, the emulsion gels with a percolating segregated network showed higher structural elasticity and thus were more resistant to large deformations, probably due to the slow relaxation of rigid, hydrodynamically interacting clusters of partially coalesced droplets. These findings could potentially aid in the design of novel emulsion gels, based on all-natural and sustainable building blocks, with specific textural and functional properties for foods, cosmetics, and pharmaceutical applications.

Glycolipid-Based Oleogels and Organogels: Promising Nanostructured Structuring Agents

Over the past few decades, the scientific community is actively involved in the development of edible structuring agents suitable for food, cosmetics, agricultural, pharmaceutical, and biotechnology applications. In particular, edible oil structuring using simple amphiphiles would be the best alternative for the currently used trans and saturated fatty acids, which cause deleterious health effects and cardiovascular problems. In this report, we have made an attempt to address the aforementioned consequences, by synthesizing a new class of structuring agents by a judicious combination of δ-gluconolactone and ricinoleic acid, compounds classified as GRAS, using simple steps in good yield. To our delight, the synthesized glycolipids self-assemble in a wide variety of vegetable oils and commercially viable glycerol, ethylene glycol, and polyethylene glycol via various intermolecular interactions to form a gel. The morphology of molecular gels was investigated by optical microscopy and FESEM analysis, which reveal the existence of a tubular architecture with a diameter ranging from 75 to 150 nm. Rheological studies disclosed the viscoelastic nature, thermal processability, and thixotropic behavior of both oleogels and organogels. Altogether, self-assembled oleogel and organogel reported in this paper would potentially be used in food, agricultural, cosmetics, pharmaceutical, and biotechnological applications.

Development of low-oil emulsion gel by solidifying oil droplets: Roles of internal beeswax concentration

There is increasing interest in the development of low-oil emulsion gels, but little is known about fabrication of low-oil emulsion gels by adjusting oil phase. Here, we reported a facile strategy to produce an ultrastable (at least 6 months) low-oil (25% oil) emulsion gels by solidifying the oil phase. The formation and stabilization mechanisms were explored. Beeswax (BW) encased liquid oil within the crystal network, forming solidified droplets. These solidified droplets promoted droplet-droplet interaction and tended to form network, further promoting gelling. Both linear and nonlinear rheology strongly supported the fact that BW enhanced the interaction of solidified droplets and strengthened the gel structure. Finally, we utilized low-oil emulsion gels as a delivery system of curcumin. The storage stabilities of curcumin at 4 and 20 °C were improved with 1, 3 and 5 wt% BW concentrations. This strategy greatly enriches emulsion gel formulations and their applications in foods.

Highly stable and thermo-responsive gel foams by synergistically combining glycyrrhizic acid nanofibrils and cellulose nanocrystals

HYPOTHESIS

Natural saponin glycyrrhizic acid (GA) and GA nanofibrils (GNFs) are effective foaming agents for formulation of aqueous food-grade foams. Through the synergistic combination of soft semiflexible GNFs with rigid nanofiller cellulose nanocrystals (CNCs), it should be possible to create advanced composite foams with a more complex structure and diverse properties including high stability and stimuli responsiveness.

EXPERIMENTS

Foams containing mixtures of GNFs and CNCs were prepared, and their formation and stability were investigated. A range of microscopy techniques and small deformation oscillatory shear were adopted to examine the microstructure and viscoelasticity of foams, and a stabilization mechanism for highly stable foams was then established. Further, the temperature-responsive destabilization of foams was evaluated.

FINDINGS

CNCs are homogeneously distributed in the architecture and mechanically reinforce the GNF fibrillar network, leading to a highly viscoelastic composite network in the continuous phase of foams, which is the key factor responsible for their high stability. Such ultra-stable gel foams display tunable thermo-responsive behavior and a rapid on-demand destabilization upon heating by inducing a phase transition of the bulk composite network. Our work opens up new scenarios on the use of a novel combination of all-natural, sustainable nanoscale building blocks to develop aqueous "superfoams" which are highly stable, stimulable and processable.

Simple, Effective, and Ecofriendly Strategy to Inhibit Droplet Bouncing on Hydrophobic Weed Leaves

Despite small-molecule surfactants and polymers being widely used as pesticide adjuvants to inhibit droplet bouncing and splashing, they still have intrinsic drawbacks either in the easy wind drift and evaporation, the unfavorable wettability, or the usage of nonrenewable resources. In this paper, we found that upon droplet impacting, 1D nanofibers assembled from natural glycyrrhizic acid (GL) could pin on the rough hydrophobic surface and delay the retraction rate of droplets effectively. Using GL as a tank-mixed adjuvant, the efficiency of glyphosate to control the weed growth was improved significantly in the field experiment, which addressed the dilemmas of current adjuvants elegantly. Our work not only provides a constructive way to overcome droplet bouncing but also prompted us to verify in future if all 1D nanofibers assembled from different small molecules can display similar control efficiencies.

Self-assembled lipids for food applications: A review

Lipids play an important role in human nutrition. Several foodstuffs can be manufactured from the simple, compound and derived lipids. In particular, the use of self-assembled lipids (SLs, e.g. self-assembled L-α-lecithin) has brought great attention for the development of tailored, tuned and targeted colloidal structures loading degradation-sensitive substances with valuable antimicrobial, antioxidant and nutraceutical properties for food applications. For example, polyunsaturated fatty acids (PUFAs) and essential oils can be protected from degradation, thus improving their bioavailability in general terms in consumers. From a nanotechnological point of view, SLs allow the development of advanced and multifaceted architectures, in which each molecule of them are used as building blocks to obtain designed and ordered structures. It is important to note before beginning this review, that simple and compound lipids are the main SLs, while essential fatty acids and derived lipids in general have been considered by many research groups as the bulk loaded substances within several structures from self-assembled carbohydrates, proteins and lipids. However, this review paper is addressed on the analysis of the lipid-lipid self-assembly. Lipids can be self-assembled into various structures (micelles, vesicular systems, lyotropic liquid crystals, oleogels and films) to be used in different food applications: coatings, controlled and sustained release materials, emulsions, functional foods, etc. SLs can be obtained via non-covalent chemical interactions, primarily by hydrogen, hydrophilic and ionic bonding, which are influenced by the conditions of ionic strength, pH, temperature, among others. This manuscript aims to give an analysis of the specific state-of-the-art of SLs for food applications, based primarily on the literature reported in the past five years.

Effect of antinutrients on heat-set gelation of soy, pea, and rice protein isolates

Plant-derived protein can present antinutrients (ANs) in its composition. The ANs can interact with the protein, affecting its solubility and functional properties, such as gelation. This work evaluated the effect of three ANs, namely phytic acid (PA), tannic acid (TA), and Quillaja bark saponin (QBS), on the gelation and solubility of soy (SPI), pea (PPI), and rice protein isolate (RPI). The ANs altered the protein isolates gelation and solubility. PA decreased the solubility and gelation of the three protein isolates at pH 3.0. The TA was the AN that most decreased the solubility and gelation characteristics of SPI and PPI at both pHs analyzed. QBS increased the gelation of SPI at pH 3.0 but decreased the final gel strength of RPI at the same pH. These results show that the knowledge of the presence of ANs in the protein isolates is of fundamental relevance for the processing of vegetable proteins.

Assembly pattern of multicomponent supramolecular oleogel composed of ceramide and lecithin in sunflower oil: self-assembly or self-sorting?

Ceramide (CER) is a novel food-grade organogelator with beneficial health effects. Lecithin (LEC) is not an effective gelator; however, it may alter the crystal morphology of the host gelator in a multicomponent system. In this paper, LEC and CER were mixed at various molar ratios in sunflower oil leading to different gelation behaviors. It was interesting since in this multicomponent system, gels formed when there was more less-effective gelator (LEC), while gels hardly formed when there was more effective gelator (CER). This drew our attention since there might not be only one kind of assembly mode between the LEC and the CER. A comprehensive rheological investigation was conducted. It was found that at specific ratios (6L4C and 5L5C), strong gels (G' > 1.0 × 105 Pa) formed with superior oil binding capacity (up to 99.84%). Meanwhile, these gels exhibited higher tolerance level to permanent deformation than the monocomponent gel. However, weak gels were observed off the optimal ratio (8L2C, 7L3C, 4L6C and 3L7C). The crystal morphology of gels drastically changed with change in gelator proportion. Short needle-like crystals and small rosette crystals were observed in 6L4C and 5L5C, respectively, while other samples exhibited spherulite-shaped crystals (8L2C, 7L3C, 4L6C, and 3L7C), which differed from any of the monocomponent gel structures (10L0C and 0L10C). Results from differential scanning calorimetry and polarized light microscopy suggested that the macroscopic properties are determined by the morphology and distribution of crystals rather than the crystallinity of the matrix. Fourier transform infrared spectroscopy results indicated the presence of van der Waals forces and the formation of hydrogen bonding between the phosphate of the LEC and the amide group of the CER. The above results indicated that the LEC and CER co-assembled at approximately equal molar ratio, and the redundant LEC or CER at other ratios self-sorted to combine with the co-assembled fibers by lateral association, leading to potentially different underlying microstructures. These multicomponent supramolecular oleogels with high tunability may further broaden their applicability in various healthy lipid-based product formats.

Review of Constituents and Biological Activities of Triterpene Saponins from Glycyrrhizae Radix et Rhizoma and Its Solubilization Characteristics

Glycyrrhizae Radix et Rhizoma is regarded as one of the most popular and commonly used herbal medicines and has been used in traditional Chinese medicine (TCM) prescriptions for over 2000 years. Pentacyclic triterpene saponins are common secondary metabolites in these plants, which are synthesized via the isoprenoid pathway to produce a hydrophobic triterpenoid aglycone containing a hydrophilic sugar chain. This paper systematically summarizes the chemical structures of triterpene saponins in Glycyrrhizae Radix et Rhizoma and reviews and updates their main biological activities studies. Furthermore, the solubilization characteristics, influences, and mechanisms of Glycyrrhizae Radix et Rhizoma are elaborated. Solubilization of the triterpene saponins from Glycyrrhizae Radix et Rhizoma occurs because they contain the nonpolar sapogenin and water-soluble sidechain. The possible factors affecting the solubilization of Glycyrrhizae Radix et Rhizoma are mainly other crude drugs and the pH of the decoction. Triterpene saponins represented by glycyrrhizin from Glycyrrhizae Radix et Rhizoma characteristically form micelles due to amphiphilicity, which makes solubilization possible. This overview provides guidance regarding a better understanding of GlycyrrhizaeRadix et Rhizoma and its TCM compatibility, alongside a theoretical basis for the further development and utilization of Glycyrrhizae Radix et Rhizoma.