Different interfaces for stabilizing liquid-liquid, liquid-gel and gel-gel emulsions: Design, comparison, and challenges.

Interfaces play essential roles in the stability and functions of emulsion systems. The quick development of novel emulsion systems (e.g., water-water emulsions, water-oleogel emulsions, hydrogel-oleogel emulsions) has brought great progress in interfacial engineering. These new interfaces, which are different from the traditional water-oil interfaces, and are also different from each other, have widened the applications of food emulsions, and also brought in challenges to stabilize the emulsions. We presented a comprehensive summary of various structured interfaces (stabilized by mixed-layers, multilayers, particles, nanodroplets, microgels etc.), and their characteristics, and designing strategies. We also discussed the applicability of these interfaces in stabilizing liquid-liquid (water-oil, water-water, oil-oil, alcohol-oil, etc.), liquid-gel, and gel-gel emulsion systems. Challenges and future research aspects were also proposed regarding interfacial engineering for different emulsions. Emulsions are interface-dominated materials, and the interfaces have dynamic natures, as the compositions and structures are not constant. Biopolymers, particles, nanodroplets, and microgels differed in their capacity to get absorbed onto the interface, to adjust their structures at the interface, to lower interfacial tension, and to stabilize different emulsions. The interactions between the interface and the bulk phases not only affected the properties of the interface, but also the two phases, leading to different functions of the emulsions. These structured interfaces have been used individually or cooperatively to achieve effective stabilization or better applications of different emulsion systems. However, dynamic changes of the interface during digestion are only poorly understood, and it is still challenging to fully characterize the interfaces.

Assessing and Comparing Potential Allergenicity of Two Partially Hydrolyzed Whey-Based Formulas for Infants: A Population-Based Study in China.

SCOPE: In cases where breast milk is unavailable or inadequate, hydrolyzed infant formula is recommended as the primary alternative. The aim of this study is to assess and compare the allergenicity of two partially hydrolyzed whey-based formulas (PHF-Ws) using serum samples from patients with cow's milk allergy (CMA). METHODS AND RESULTS: LC-MS/MS technology is used to investigate the peptide distribution in both samples. The immunoreactivity of two PHF-Ws in 27 serum samples from 50 Chinese infants (02 years) with CMA is analyzed. The results demonstrate that even with a similar a degree of hydrolysis (DH), primary protein sources, peptides with molecular weights <5 kDa, and differences in the number of residual allergenic epitopes in the hydrolyzed peptide segments can lead to varying immune responses. CONCLUSION: The two PHF-Ws have notably high intolerance rates, exceeding 10% among infants with CMA. Therefore, suggesting that PHF-Ws may not be suitable for infants and children with CMA in China.

Undenatured type II collagen nanofibrils with sodium alginate coating: Structural characterization, physicochemical properties and capability to load curcumin.

In this study, the structural design and physicochemical property enhancement of undenatured type II collagen (UC-II) nanofibrils with sodium alginate (SA) coating induced by calcium ions (Ca2+) were investigated. The research aimed to elucidate the impact of Ca2+ concentration on the morphology, thermal stability, and digestive resistance, as well as to assess the potential of UC-II/SA nanofibrils as a delivery system for curcumin (Cur). A series of Ca2+ concentrations (1-9 mM) were methodically applied to optimize the condition that maintains the triple-helical structure of UC-II, thereby enhancing its functional properties. It was found that the Ca2+ level up to 5 mM effectively preserved the structural integrity and improved thermal stability of UC-II, with the added benefit of ensuring the substantial delivery of active fragment to small intestine (70.7 %), which was 3.43 times greater than that of uncoated UC-II. Moreover, incorporating Cur into the UC-II/SA nanofibrils resulted in a 300 times increase in Cur solubility and showcased the superior dispersion stability, antioxidant activity, and sustained release profile during simulated digestion. These findings underscored the dual functionality of the UC-II/SA system as both a stabilizing agent for UC-II nanofibrils and an efficient carrier for Cur delivery.

Stabilization of oil-in-water high internal phase emulsions with octenyl succinic acid starch and beeswax oleogel.

High internal phase emulsions (HIPEs) based on beeswax (BW) oleogels and octenyl succinic acid starch (OSA starch) were prepared by a facile one-step method. Effects of the oleogelation of internal phase on the formation, stability and functionality of the HIPEs were investigated. OSA starch absorbed at the interface allowed high surface charge (|ζ| > 25 mV) of the droplets, and small droplet size (d ≈ 5 m). Microstructural observation suggested that the HIPEs were of O/W type with droplets packed tightly. With the increase in BW content (0-4 %), the particle size (4-7 µm) and ζ-potential (-25 ~ -30 mV) of the HIPEs were first decreased and then increased. Stability analysis revealed that the addition of BW effectively improved emulsion stability against centrifugation, freeze-thawing, changes in pH and ionic strength, and the HIPE with 2 % BW presented the best stability. Rheological tests indicated that the HIPEs with higher content of BW exhibited higher storage modulus, solid-like properties, and shear thinning behaviors. Creep-recovery results implied that the oleogelation enhanced the structure of HIPEs and improved the deformation resistance of the systems. When subjected to light and heat, oleogel-in-water HIPEs showed advantages in protecting ß-carotene from degradation, and ß-carotene in the HIPEs with 2 % BW had the lowest degradation rate. These findings suggested that gelation of oil phase could improve the stability of HIPEs and the encapsulation capability, which would be meaningful for the development of novel healthy food.

Structural modification of zein-based oil-in-glycerol emulsion gels for improved textural and digestion behaviors.

Zein can dissolve in glycerol, and can be developed into oil-in-glycerol emulsion gels to widen its applications. The current study focused on modulating the structures of zein-based emulsion gels by the addition of a surface active ingredient (Span 20, SP) to improve textural and digestion behaviors. Microstructural observation indicated that the addition of SP replaced zein from the oil-glycerol interface, and allowed a higher level of oil droplet aggregation. After adding SP, the gel hardness decreased from 3.43 ± 0.14 N to 1.62 ± 0.01 N, and the storage modulus also decreased with the increase of SP content. Viscoelasticity of the gels was thermo-responsive, and the presence of SP contributed to a higher recovery of the storage modulus after the heating-cooling process. The addition of SP reduced the oil-binding capacity of zein gel from 97.61 ± 0.19% to 82.00 ± 0.92% and the solvent-binding capacity from 75.97 ± 3.05% to 62.25 ± 0.22%, indicating that the zein network was weakened. Then, gels were mixed with simulated digestive juices to track the changes of gel structures and the release of free fatty acids. The addition of SP accelerated the digestion process, especially intestinal digestion. SP contributed to a higher fluorescence intensity in the digesta, which was a sign of a higher level of digestion of zein. Subsequently, the addition of SP increased the release content of free fatty acids from 4.27 ± 0.71% to 5.07 ± 1.27%. The above findings would be useful in designing zein-based functional food products with favored textural and digestion properties.

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

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

Enhanced freeze-thawing stability of water-in-oil Pickering emulsions stabilized by ethylcellulose nanoparticles and oleogels.

This study developed water-in-oil (W/O) Pickering emulsions stabilized by ethylcellulose (EC) nanoparticles and EC oleogels, which presented significantly improved freeze-thawing (F/T) stability. Microstructural observation suggested EC nanoparticles were distributed at the interface and within the water droplets, and the EC oleogel trapped oil in the continuous phase. Freezing and melting temperatures of water in the emulsions with more EC nanoparticles were lowered and the corresponding enthalpy values were reduced. F/T led to lower water binding capacity but higher oil binding capacity of the emulsions, compared to the initial emulsions. Low field-nuclear magnetic resonance confirmed the increased mobility of water but decreased mobility of oil in the emulsions after F/T. Both linear and nonlinear rheological properties proved that emulsions exhibited higher strength and higher viscosity after F/T. The widened area of the elastic and viscous Lissajous plots with more nanoparticles suggested the viscosity and elasticity of emulsions were increased.

Effects of different mechanical processes on the structural and powdery properties of insoluble undenatured type II collagen.

This study aimed to investigate the effects of dynamic high-pressure homogenization (DHPH), dynamic high-pressure microfluidization (DHPM), and wet media milling (WMM) processes on the particle size, microstructure, triple helix structure, wettability and suspension stability of insoluble undenatured type II collagen (IUC-II). The structural and powdery properties were regulated by different processes and parameters. By contrast, WMM-treated IUC-II showed smallest particle size (15.70 µm), highest wetting rate (216.94 mm/h) and best suspension stability. However, individual mechanical processes caused partial disruption of IUC-II triple helix structure. Low-acyl gellan gum (LAGG) could bind to IUC-II through hydrogen bonds and hydrophobic interactions, which protected the triple helix structure and further enhanced powdery properties of IUC-II treated by WMM process, but restrained the soluble transition during digestion. These results demonstrated that WMM process was more suitable for enhancing powdery properties of IUC-II, while the triple helix structure of IUC-II could be effectively protected by LAGG.

Nanostructured lipid carriers (NLCs) stabilized by natural or synthetic emulsifiers for lutein delivery: Improved physicochemical stability, antioxidant activity, and bioaccessibility.

This study investigated the impacts of individual emulsifiers on the physicochemical stability, antioxidant ability, and in vitro digestion behavior of lutein-loaded nanostructured lipid carriers (NLCs). NLCs particles stabilized by ethyl lauroyl arginate, rhamnolipid, or tea saponin were fabricated by high-pressure microfluidization method. Differential scanning calorimetry and X-ray diffraction results confirmed the regulatory effect of emulsifiers on the crystallization behavior of NLCs. NLCs stabilized by rhamnolipid presented higher encapsulation efficiency (94.73%) for lutein than those stabilized by tea saponin (90.39%) or ethyl lauroyl arginate (88.86%). Meanwhile, the stability of embedded lutein during storage or photothermal treatments was greatly enhanced. Individual emulsifiers, together with lutein, endowed NLCs with excellent antioxidant capacity. During in vitro digestion, rhamnolipid-stabilized NLCs showed the slowest release of free fatty acids (50.87%) and provided an optimal sustained release for lutein with relatively high bioaccessibility (23.01%).

In Vitro Digestion and Storage Stability of ß-Carotene-Loaded Nanoemulsion Stabilized by Soy Protein Isolate (SPI)-Citrus Pectin (CP) Complex/Conjugate Prepared with Ultrasound.

In this study, we employed the ultrasound-prepared electrostatic complex and covalent conjugate of soy protein isolate (SPI) and citrus pectin (CP) to prepare ß-carotene-loaded nanoemulsions. The in vitro digestion and storage stability of nanoemulsions stabilized by different types of emulsifiers were investigated and compared. Nanoemulsions stabilized by ultrasound-treated complex/conjugate showed the highest encapsulation efficiency; during gastric digestion, these nanoemulsions also demonstrated the smallest droplet sizes and the highest absolute values of zeta potential, indicating that both electrostatic complexation/covalent conjugation and ultrasound treatment could significantly improve the stability of the resulting nanoemulsions. In comparison, complexes were more beneficial for the controlled release of ß-carotene; however, the conjugate-stabilized nanoemulsion showed an overall higher bioaccessibility. The results were also confirmed by optical micrographs. Furthermore, nanoemulsions stabilized by ultrasound-prepared complexes/conjugates exhibited the highest stability during 14-day storage at 25 °C. The results suggested that ultrasound-prepared SPI-CP complexes and conjugates had great application potential for the delivery of hydrophobic nutrients.

Rheology and Tribology of Ethylcellulose-Based Oleogels and W/O Emulsions as Fat Substitutes: Role of Glycerol Monostearate.

Rheological and tribological properties of oleogels and water-in-oil (W/O) emulsions are important for application in fat substitutes. This study investigated the roles of glycerol monostearate (GMS) in tailoring the structural, rheological and tribological properties of ethylcellulose (EC)-based oleogels and W/O emulsions as potential fat substitutes. The addition of GMS contributed to more round and compact oil pores in oleogel networks. The oleogel with 5% GMS had higher crystallinity, leading to solid state (lower tanδ value), mechanical reversibility (higher thixotropic recovery), but a brittle (lower critical strain) structure in the samples. GMS gave the oleogels and emulsions higher oil binding capacity, storage modulus and yield stress. Under oral processing conditions, GMS addition contributed to higher textural attributes and viscosity. Friction coefficients in mixed and boundary regions of oleogels and emulsions were reduced with the increase in GMS content from 0~2%, but increased with 5% GMS. Rheological and tribological properties of lard, mayonnaise and cream cheese can be mimicked by EC oleogels with 5% GMS, or emulsions with 2% GMS and 2-5% GMS, respectively. The study showed the potentials of oleogel and W/O emulsions in designing low-fat products by tuning the structures for healthier and better sensory attributes.

Structural characterization of hydrogel-oleogel biphasic systems as affected by oleogelators.

This work developed novel bi-phasic gel systems containing a hydrogel (κ-carrageenan) and an oleogel, and investigated the roles of different oleogelators (glycerol monostearate-GMS and beeswax-BW) on the structures of the bigels. Stable bigels were obtained via a facile blending approach by carefully controlling the mixing temperature. Microstructural observation indicated that GMS-based bigels were of oil-in-water type, and BW-based bigels were of water-in-oil type. In GMS-based bigels, both water holding capacity and oil holding capacity after freeze-thawing were enhanced with the increase in GMS content. The bigel with 8% (w/w) GMS had water holding capacity and oil holding capacity of 94.81% and 93.13%, respectively. In BW-based bigels, oil holding capacity was also increased (from 36.98% to 88.39%), but separation of oleogel and hydrogel was detected after centrifugation. Textural and rheological analysis revealed that gel strength of the bigels were gradually increased with the increase in oleogelator content, and BW-based bigels were much stronger than GMS-based ones. Moreover, BW-based bigels had higher relaxation degree. DSC analysis found that thermodynamic stability of the bigels were increased with the increase in oleogelator content. Temperature sweep rheological analysis indicated that GMS-based bigels were not able to fully recover their original structure and gel strength after heating-cooling cycle due to the nature of the crystals formed in bigels. This study offered profound structural information about the bigels as affected by different oleogelators, which was also useful for the development of novel functional products.

Cyclodextrin-based metal-organic framework nanoparticles as superior carriers for curcumin: Study of encapsulation mechanism, solubility, release kinetics, and antioxidative stability.

In this paper, we propose a facile program of preparing nanoscale γ-cyclodextrin-based metal-organic frameworks (Nano-CD-MOFs) for the encapsulation of curcumin. Such Nano-CD-MOFs not only possess excellent mono-dispersity and crystalline structure, but also perform superior loading capacity. The results of N2 adsorption-desorption, XRD, DSC, and microtopography are utilized to confirm the presence status of encapsulated curcumin and further reveal the encapsulation mechanism of Nano-CD-MOFs. Curcumin-loaded Nano-CD-MOFs (Cur-Nano-CD-MOFs) dramatically increase curcumin solubility and a top-down uniform dispersion in the dissolution process. The perfect fitting of First-order and Korsmeyer-Peppas models suggests that the release performance of Nano-CD-MOFs is controlled by the loaded quantity of curcumin and related to Fickian diffusion. Moreover, the antioxidative stability of Cur-Nano-CD-MOFs is considerably enhanced even after 120 min of persistent ultraviolet irradiation. Therefore, we suggest that such Nano-CD-MOFs can be promoted as an advanced carrier for the delivery of curcumin or other nutraceuticals.

W/O emulsions featuring ethylcellulose structuring in the water phase, interface and oil phase for multiple delivery.

This study reported a novel approach to stabilize W/O emulsions with nanoparticles and oleogel from ethylcellulose (EC), and the emulsions were applied for multiple delivery. Microstructural observations revealed that EC nanoparticles were distributed within the water droplets and at the interface, and EC oleogel was in the continuous phase. Storage modulus and viscosity were higher, and thixotropic structural recovery rates were lower, in the emulsions with more EC nanoparticles. Both EC nanoparticles and oleogels worked to stabilized the emulsions upon freeze-thawing, as only minor water or oil was released. Upon heating, some EC nanoparticles transited from the interface to the oil phase, and water droplets were aggregated. The interface was recreated when the samples were re-emulsified. When curcumin and anthocyanin were incorporated, both bioactives had improved light stability. During in vitro study, curcumin was mostly released at the early stage of intestinal digestion, while anthocyanin was released at later stage.

Characterization and antioxidant properties of chitosan film incorporated with modified silica nanoparticles as an active food packaging.

In this study, two modified silica nanoparticles (SiO2-GA NPs) were successfully obtained by covalently grafting gallic acid onto silica nanoparticles. The mean particle diameters of their were 112.7 ± 0.55 nm (1-SiO2-GA NPs) and 408.7 ± 3.20 nm (4-SiO2-GA NPs), respectively. Novel antioxidant active packaging composite films were prepared by incorporation of 1-SiO2-GA NPs or 4-SiO2-GA NPs into chitosan. The structure analysis of the composite films showed that intermolecular hydrogen bonds were formed between the two modified silica nanoparticles and chitosan. Compared with the chitosan film, the mechanical properties, water vapor barrier property and UV light barrier ability of the composite films were significantly improved. Moreover, the incorporated of the two modified silica nanoparticles significantly increased antioxidant activity of the composite films. This study indicates that composite films incorporated with modified silica nanoparticles, especially the incorporation of 1-SiO2-GA NPs can be used as novel antioxidant food packaging composite films.

Superfruits in China: Bioactive phytochemicals and their potential health benefits - A Review.

The term "superfruit" usually refers to certain fruits, which are rich in antioxidant components, therefore, are beneficial to human health. In China, there has been the concept of health preservation and dietary therapy through food intake in a long history. However, some other superfruits growing mainly in China have not attracted extensive attention, such as Cili, Goji berry, and sea buckthorn. Many studies suggested all of these superfruits showed strong antioxidant effects and anti-inflammatory activity in common. However, there are various other advantages and functions in different fruits. This article reviewed the research findings from the existing literature published about major antioxidant bioactive compounds and the potential health benefits of these fruits. The phytochemicals from superfruits are bioaccessible and bioavailable in humans with promising health benefits. More studies are needed to validate the health benefits of these superfruits. It would provide essential information for further research and functional food development.

Enhanced stability and controlled gastrointestinal digestion of ß-carotene loaded Pickering emulsions with particle-particle complex interfaces.

In this study, we used large, rigid, and hydrophilic zein-propylene glycol alginate composite particles (ZPCPs) and small, soft, and hydrophobic whey protein microgel (WPM) particles to synergistically stabilize a Pickering emulsion for delivery of ß-carotene. The photothermal stability and storage stability of ß-carotene were improved with the combined use of different particles. Microstructural observations showed that ZPCPs were effectively adsorbed at the oil/water interface despite the substantial interparticle gaps. WPM particles could swell and stretch on the interface due to their deformable structure, thereby forming an interfacial layer of flattened particles to cover a large surface area. The interfacial structure and macroscopic properties of Pickering emulsions were modulated by adjusting the mass ratio and addition sequence of different particles. The combination of ZPCPs and WPM delayed the lipolysis during gastrointestinal digestion. Through controlling the composition of the complex interface, the free fatty acid (FFA) release rate of Pickering emulsions in the small intestinal phase was reduced from 15.64% to 9.03%. When ZPCPs were used as the inner layer and WPM as the outer layer and the mass ratio of ZPCPs to WPM was 4 : 1, the Pickering emulsion showed the best stability and ß-carotene bioaccessibility. The Pickering emulsion with particle-particle complex interfaces could be applied in foods and pharmaceuticals for the purpose of enhanced stability, delayed lipolysis or sustained nutrient release.

Zein Colloidal Particles and Cellulose Nanocrystals Synergistic Stabilization of Pickering Emulsions for Delivery of ß-Carotene.

In this study, we utilized different types of particles to stabilize ß-carotene-loaded Pickering emulsions: spherical hydrophobic zein colloidal particles (ZCPs) (517.3 nm) and rod-shaped hydrophilic cellulose nanocrystals (CNCs) (115.2 nm). Either of the particles was incapable of stabilizing Pickering emulsions owing to their inappropriate wettability. When the mass ratio of ZCPs and CNCs was 1:4, the Pickering emulsion showed the best physical and photothermal stability. Compared to the ZCP-stabilized Pickering emulsion (9.29%), the retention rate of ß-carotene in the Pickering emulsion costabilized by ZCPs and CNCs was increased to 60.23% after 28 days of storage at 55 °C. Confocal microscopy and cryoscanning electron microscopy confirmed that different types of particles could form a multilayered structure or induce the formation of an interparticle network. Furthermore, the complexation of ZCPs and CNCs delayed the lipolysis of the emulsion during in vitro digestion. The free fatty acid (FFA) release rate of Pickering emulsions in the small intestinal phase was reduced from 19.46 to 8.73%. Accordingly, the bioaccessibility of ß-carotene in Pickering emulsions ranged from 9.14 to 27.25% through adjusting the mass ratio and addition sequence of distinct particles at the interface. The Pickering emulsion with the novel particle-particle complex interface was designed in foods and pharmaceuticals for purpose of enhanced stability, delayed lipolysis, or sustained nutrient release.

Development of curcumin loaded core-shell zein microparticles stabilized by cellulose nanocrystals and whey protein microgels through interparticle interactions.

Novel multilayered core-shell microparticles were developed to deliver curcumin using positively charged zein microparticles coated with negatively charged cellulose nanocrystals (CNCs) and positively charged whey protein microgels (WPMs) at pH 4. Different levels of WPMs (0.10%-1.50%, w/v) were utilized to regulate the structure, stability, and in vitro digestion of curcumin loaded zein-CNC core-shell microparticles. The size of zein-CNC-WPM core-shell microparticles ranged from 2087.7 to 2928.2 nm. The electrostatic attraction and hydrogen bonding were mainly involved in the assembly of the core-shell microparticles through particle-particle interactions. The microstructure of the core-shell microparticles was dependent on the level of the WPM. When its appropriate level was adopted (0.50%-1.00%, w/v), the WPM formed a protective shell for zein-CNC-WPM core-shell microparticles. The retention rate of curcumin in the core-shell microparticles increased by 47.56% and 32.79% during light and thermal treatment, respectively. Excess microgels facilitated the bridging aggregation and formation of a network structure on the particle surface, which further reduced their stability and greatly restricted the curcumin release. The potential of nanosized protein microgels was explored to stabilize and modulate the physicochemical properties of multilayered core-shell microparticles through interparticle interactions.

Structural design of zein-cellulose nanocrystals core-shell microparticles for delivery of curcumin.

The novel core-shell microparticles were fabricated to deliver curcumin by using hydrophobic zein microparticles as the core and hydrophilic cellulose nanocrystals (CNCs) as the shell. Different concentrations (0.10-1.50%, w/v) of CNCs were utilized to regulate the microstructure, physicochemical stability, and in vitro digestion of the core-shell microparticles. The size of the microparticles ranged from 1017.3 to 3663.7 nm. Electrostatic attraction and hydrophobic interactions were responsible for the assembly of zein-CNCs core-shell microparticles. The microstructure of the microparticles was dependent on the CNCs level. The retention rate of curcumin in the core-shell microparticles was increased by 76.41% after UV radiation. Furthermore, the rise of CNCs level delayed the release of curcumin from the microparticles in gastrointestinal tract and reduced its bioaccessibility. The potential of utilizing hydrophilic nanoparticles was explored to stabilize hydrophobic microparticles through interparticle interactions, which was useful to develop the novel core-shell microparticles for the application in functional foods.