Emulsion microgel particles: Novel encapsulation strategy for lipophilic molecules

Impact of pH on the fabrication of egg white reinforced soy protein composite microgels for gastrointestinal delivery purposes

Protein molecules such as soy protein isolate (SPI) and egg white (EW) are highly promising materials for developing hydrogels (especially micro/nanogels) for the encapsulation, protection and controlled release of bioactive substances. However, there are limited numbers of studies on the formulation and behavior of these two gelling materials as microgels. In our study, composite microgels of SPI and EW at various component ratios and pH conditions have been successfully prepared; the rheological behavior and structural properties of these composite microgels before, during and after in vitro digestion have been analyzed; and their performance in curcumin encapsulation and gastrointestinal delivery has also been investigated. It was concluded that the SPI-EW composites at a mass ratio of 50 : 50 showed the best gelling properties in terms of storage modulus. Composite microgels prepared at pH 4 had larger particle sizes with more compact structures than those prepared at pH 7, due to their acidic complex coacervation, and therefore were more resistant to gastrointestinal digestion. The results suggest that the SPI-EW composite microgel particles prepared at pH 4 could achieve better sustained-release of curcumin in the in vitro gastrointestinal tract, with preserved antioxidant activity. Our study shows promise for the utilization of protein-based composite micro/nanogels for oral delivery applications.

Recent research and applications in lipid-based food and lipid-incorporated bioink for 3D printing

Three-dimensional (3D) printing, as an emerging digital production technology, has recently been receiving increasing attention in food processing. It is important to understand the effect of key ingredients of food materials on the printing, which makes it possible to achieve a wider range of structures using few nozzles and to provide tailored nutrition and personalization. This comprehensive review delves into the latest research on 3D-printed lipid-based foods, encompassing a variety of products such as chocolate, processed cheese, as well as meat. It also explores the development and application of food bioinks that incorporate lipids as a pivotal component, including those based on starch, protein, oleogels, bigels, and emulsions, as well as emulsion gels. Moreover, this review identifies the current challenges and presents an outlook on future research directions in the field of 3D food printing, especially the research and application of lipids in food 3D printing.

Development of injectable microgel-based scaffolds via enzymatic cross-linking of hyaluronic acid-tyramine/gelatin-tyramine for potential bone tissue engineering

Currently, the healing of large bone defects relies on invasive surgeries and the transplantation of autologous bone. As a less invasive treatment option, the provision of microenvironments that promote the regeneration of defective bones holds great promise. Here, we developed hyaluronic acid (HA)/gelatin (Ge) microgel-based scaffolds to guide bone regeneration. To enable the formation of microgels by enzymatic cross-linking in the presence of horseradish peroxidase (HRP) and hydrogen peroxide (H2O2), we modified the polymers with tyramine (TA). Spectrophotometry and proton nuclear magnetic resonance (1H NMR) spectroscopy analysis confirmed successful tyramine substitution on polymer backbones. To enable the formation of microgels by a water-in-oil emulsion approach, the HRP and H2O2 concentrations were tuned to achieve the gelation in a few seconds. By varying the stirring speed from 600 to 1000 rpm, spherical microgels were produced with an average size of 116 ± 8.7 and 68 ± 4.7 μm, respectively. The results showed that microgels were injectable through needles and showed good biocompatibility with the cultured human osteosarcoma cell line (MG-63). HA/Ge-TA microgels served as a promising substrate for MG-63 cells since they improved the alkaline phosphatase activity and level of calcium deposition. In summary, the developed HA/Ge-TA microgels are promising injectable microgel-based scaffolds in bone tissue engineering.

Preparation of shellac nanoparticles-chitosan complexes stabilized Pickering emulsion gels and its application in β-carotene delivery

Shellac nanoparticles (SNPs)-based Pickering emulsion gels show promise as delivery carriers but face challenges due to poor emulsifying properties. This study aimed to fabricate stable emulsion gels using SNPs and chitosan (CS) complexes, creating a β-carotene delivery system. The effects of oil phase fractions, emulsifier concentrations and SNPs/CS ratios on rheological properties and the structural properties of emulsion were investigated. The formation of SNPs/CS complexes was through hydrogen bonding and electrostatic interactions. By adjusting the SNPs/CS ratio to 1/0.33, the contact angle of the complexes was optimized to approximately 90°. SNPs/CS complexes served dual roles as emulsifiers and gelling agents in the emulsion gels. Notably, the gel strength (storage modulus) of the emulsion gels remained unchanged after the encapsulation of β-carotene. Emulsion gels with SNPs/CS (1/0.25) complexes showed the highest β-carotene bioaccessibility at 80.4 %. Furthermore, this system could expand the use of shellac-based emulsion gels in food applications.

Fabrication, digestion behavior and β-carotene bioaccessibility of emulsion-filled double-network gel: Effect of corn fiber gum/soy protein isolate ratio and surfactant types

Emulsion fortified with β-carotene was added to corn fiber gum (CFG)/soy protein isolate (SPI) double network gel matrix to obtain emulsion-filled gels (EFG) via dual induction of laccase and glucono-δ-lactone. Protein digestion was accompanied by the release of β-carotene from gel matrix during in vitro digestion. The surfactant types and corn fiber gum/soy protein isolate ratio affected the β-carotene bioaccessibility via changing oil-water interfacial composition and emulsion particle size during in vitro digestion. As compared with Tween-20 EFGs, emulsion droplets released from SPI EFGs was more susceptible to flocculation, followed with coalescence due to proteolysis of interfacial SPI during gastric digestion. The resulting oil droplets with large particle size exhibited lower lipase adsorption, thus reducing the free fatty acid content and β-carotene bioaccessibility. The confocal laser scanning microscope (CLSM) observation confirmed that protein hydrolysate from gel matrix were adsorbed onto the oil-water interface competing with Tween-20 during intestinal digestion. For EFGs with higher CFG content, steric hindrance of CFG molecules and less emulsion release could inhibit droplet flocculation, thus enhancing β-carotene bioaccessibility.

Influence of gelatinized octenyl succinic anhydride-modified waxy adlay seed starch on the properties of astaxanthin-loaded emulsions: Emulsion properties, stability and in vitro digestion properties

Octenyl succinic anhydride (OSA)-modified starch is a commonly used food emulsifier and its emulsifying properties are positively correlated with the degree of substitution (DS). However, the maximum concentration of OSA in starch approved by the FDA and the China National Food Safety Standards is 3%. This study aims to enhance the emulsifying properties of OSA-modified waxy adlay seed starch by gelatinization under a limited DS and investigate its use in preparing delivery systems. The gelatinized OSA starch exhibited a more flexible macromolecular structure and better emulsifying activity (20.19 m2/g). The gelatinized OSA starch-stabilized astaxanthin-loaded emulsions showed high retention of astaxanthin (>50%) and long-term stability (56 days). In vitro digestion, the emulsion system showed a protective effect on astaxanthin, and the bioaccessibility of astaxanthin was increased to 16.32%. This study indicated that gelatinization could enhance the emulsifying properties of OSA starch, and this starch-stabilized emulsion was an effective system for astaxanthin.

Preparation, Characterization and Formation Mechanism of High Pressure-Induced Whey Protein Isolate/κ-Carrageenan Composite Emulsion Gel Loaded with Curcumin

In order to explore the formation mechanism of the emulsion gel induced by high pressure processing (HPP) and its encapsulation and protection of functional ingredients, a curcumin-loaded whey protein isolate (WPI)/κ-carrageenan (κ-CG) composite emulsion gel induced by HPP was prepared. The effect of pressure (400, 500 and 600 MPa), holding time (10, 20 and 30 min) and concentration of κ-CG (0.8%, 1.0% and 1.2%, w/v) on the swelling rate, gel strength, the stability of curcumin in the emulsion gel, water distribution and its mobility, as well as the contents of interface protein were characterized. The results showed that the addition of κ-CG significantly reduced the protein concentration required for the formation of emulsion gel induced by HPP and greatly reduced the swelling rate of the emulsion gel. The gel strength and storage stability of the composite emulsion gels increased with the increase in pressure (400-600 MPa) and holding time (10-30 min). When the pressure increased to 500 MPa, the stability of curcumin in the emulsion gel significantly improved. When the ratio of WPI to κ-CG was 12:1 (the κ-CG concentration was 1.0%), both the photochemical and thermal stability of curcumin were higher than those of the other two ratios. The HPP significantly increased the mobility of monolayer water in the system, while the mobility of multilayer water and immobilized water was significantly reduced. Increasing the holding time and the concentration of κ-CG both can result in an increase in the interfacial protein content in the oil/water system, and the HPP treatment had a significant effect on the composition of the interfacial protein of the emulsion gel.

Microgel delivery systems of functional substances for precision nutrition

Microgels delivery system have great potential in functional substances encapsulation, protection, release, precise delivery and nutritional intervention. Microgel is a three-dimensional network structure formed by physical or chemical crosslinking of biopolymers, whose characteristics include dispersion and swelling, stable structure, small volume and high specific surface area, and is a special kind of colloid. In this chapter, the common wall materials for preparing food grade microgels, and the main preparation principles, methods, advantages and disadvantages of microgels loaded with functional substances were firstly reviewed. Then the main characteristics of microgel as delivery system, such as deformability, high encapsulation, stimulus-responsive release and targeted delivery, and its potential benefits in intervening chronic diseases were summarized. Finally, the applications of microgel delivery system for functional substance in the field of precision nutrition were discussed. This chapter will help to design of next-generation advanced targeting microgel delivery system, and realize precision nutrition intervention of food functional substances on body health.

Modulating peppermint oil flavor release properties of emulsion-filled protein gels: Impact of cross-linking method and matrix composition

For some food applications, it is desirable to control the flavor release profiles of volatile flavor compounds. In this study, the effects of crosslinking method and protein composition on the flavor release properties of emulsion-filled protein hydrogels were explored, using peppermint essential oil as a model volatile compound. Emulsion-filled protein gels with different properties were prepared using different crosslinking methods and gelatin concentrations. Flavor release from the emulsion gels was then monitored using an electronic nose, gas chromatography-mass spectrometry (GC-MS), and sensory evaluation. Enzyme-crosslinked gels had greater hardness and storage modulus than heat-crosslinked ones. The hardness and storage modulus of the gels increased with increasing gelatin concentration. For similar gel compositions, flavor release and sensory perception were faster from the heat-crosslinked gels than the enzyme-crosslinked ones. For the same crosslinking method, flavor release and perception decreased with increasing gelatin concentration, which was attributed to retardation of flavor diffusion through the hydrogel matrix. Overall, this study shows that the release of hydrophobic aromatic substances can be modulated by controlling the composition and crosslinking of protein hydrogels, which may be useful for certain food applications.

Physicochemical properties and in vitro digestion behavior of emulsion micro-gels stabilized by κ-carrageenan and whey protein: Effects of sodium alginate addition

Emulsion micro-gels exhibit significant potential as functional ingredients for modifying food texture, replacing saturated fats, or serving as templates for the controlled release of bioactive compounds. Structural design principles are being applied more frequently to develop innovative emulsion micro-gels. In this paper, whey protein concentrate (WPC), κ-carrageenan and sodium alginate (SA) were utilized for preparing emulsion micro-gels. To reveal the regulation mechanism of the structural and physicochemical properties of emulsion micro-gels on lipid digestion, the influence of SA additions on the structural, physicochemical properties and in vitro digestion behavior of κ-carrageenan/WPC-based emulsion micro-gel were explored. The FTIR results suggest that the emulsion micro-gels are formed through non-covalent interactions. With the increase of SA addition (from 0.7 g/100 mL to 1.0 g/100 mL), the decreased mean droplet size, the increased hardness, elasticity indexes, and water holding capacity, the reduced the related peak times all indicated that the emulsion micro-gels exhibit enhanced rheological, stability, and mechanical properties. It can be concluded from the microstructure, particle size distribution of the emulsion micro-gels during simulated digestion and free fatty acid release that both κ-carrageenan/WPC-based emulsion micro-gel and κ-carrageenan/WPC/SA-based emulsion micro-gel can inhibit lipid digestion due to the ability to maintain structural stability and hindering the penetration of bile salts and lipase through the hydrogel networks. And the ability is regulated by the binding properties the gel matrix and oil droplets, which determine the structure and physicochemical properties of emulsion micro-gels. The research suggested that the structure of emulsion micro-gels can be modified to produce various lipid digestion profiles. It may be significant for certain practical application in the design of low-fat food and controlled release of bioactive agents.

Comparison on emulsifying and emulgelling properties of low methoxyl pectin with varied degree of methoxylation from different de-esterification methods

Low methoxyl pectin (LMP) with different degree of methoxylation (DM, 40-50 %, 20-30 % and 5-10 %) were prepared from commercially available citrus pectin using high hydrostatic pressure assisted enzymatic (HHP-pectin) and traditional alkaline (A-pectin) de-esterification method. The results showed that both de-esterification methods and DM exhibited LMPs with varied physicochemical, structural, and functional properties. As the DM decreased, LMP showed a decrease in molecular weight (Mw), while an increase in negative charges and rhamnogalacturonan I (RG-I) ratio, accompanied with better emulsion stability, emulsion gel strength and water-holding properties. Relative to A-pectin, HHP-pectin had higher Mw and lower RG-I side chain ratio, contributing to its better thermal stability, apparent viscosity, and emulgelling properties. HHP-pectin with lower DM (5-10 %) showed superior thickening, emulsifying and emulgelling properties, while that with higher DM (40-45 %) had superior thermal stability, which provided alternative for de-esterification and targeted structural modification of pectin.

Lupin protein-stabilized oil droplets contribute to structuring whey protein emulsion-filled gels

This work aimed to understand the role of lupin protein or mixed lupin-whey protein stabilized oil droplets on the texture and microstructure of a heat-induced whey protein gel. Protein-stabilized emulsions were compared to surfactant-stabilized emulsions to investigate the potential of their interfacial interactions to impart unique structures in the filled gels. The structure development was followed in situ using rheology and the final heat-induced gels were characterized by small and large amplitude oscillatory rheology and confocal microscopy. The development of the gel modulus as well as the final gel properties were linked to the type of interactions between the whey protein matrix and the protein adsorbed at the oil interface. The final gels were selectively dissolved in various buffers, and the results showed that replacing interfacial whey protein with lupin protein resulted in a reduced amount of disulfide bridges, explaining the softer gel in the lupin containing gels compared to those with whey protein. Non-covalent interactions were the main forces involved in the formation of actively filled droplets in the gel network. This work demonstrated that by modulating the interfacial composition of the oil droplets, differing gel structures could be achieved due to differences in the protein-protein interactions between the continuous and the interfacial phase. There is therefore potential for the development of innovative products using lupin-whey protein mixtures, by careful control of the processing steps and the matrix composition.

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.

Characterizations of emulsion gel formed with the mixture of whey and soy protein and its protein digestion under in vitro gastric conditions

Partially replacing animal proteins with plant proteins to develop new products has much attention. To get knowledge of their application in emulsion gels, heat-induced composite protein emulsion gels were fabricated using the mixtures of whey protein isolate (WPI) and soy protein isolate (SPI) with the final total protein concentration of 10% (w/w). The water holding capacity (WHC), mechanical and rheological properties and microstructure of mixed protein emulsion gels prepared at different WPI to SPI ratios (100:0, 90:10, 70:30, 50:50, 30:70, 10:90, 0:100, w/w) were investigated. The ratios of WPI to SPI showed little effect on the WHC of the mixed protein emulsion gels (p > 0.05). Increasing the ratio of SPI decreased the hardness and storage modulus (G') of mixed protein emulsion gels, whereas the porosity of mixed protein emulsion gels in the microstructure increased, as shown by CLSM. Both β-lactoglobulin and α-lactalbumin from WPI and 7 S and 11 S from SPI participated in forming the gel matrix of mixed protein emulsion gels. More protein aggregates existed as the gel matrix filler at the high soy protein levels. Interestingly, the G' of mixed protein emulsion gels at the WPI to SPI ratio of 50:50 was higher than the sum of G' of individual WPI and SPI emulsion gels. The whey protein network predominated the gel matrix, while soy protein predominated in the active filling effect. When subjected to an in vitro dynamic gastric digestion model, soy protein in the gels (WPI:SPI = 50:50) degraded faster than whey protein during gastric digestion. This study provided new information on the characteristics of composite protein emulsion gel fabricated with the WPI and SPI mixture.

Structured Emulgels by Interfacial Assembly of Terpenes and Nanochitin

Interfacial assemblies formed by colloidal complexation are effective in multiphase stabilization, as shown in structured liquids and Pickering emulgels. Herein, we demonstrate a type of biobased colloidal system that spontaneously stabilizes an organic phase in a continuous hydrogel phase. Specifically, a triterpene extracted from bark (betulin, BE) is added to an organic phase containing a coniferous resin (rosin acid, a diterpene). BE is shown to take part in strong noncovalent interactions with the nanochitin dispersed in the aqueous (hydrogel) phase, leading to a complex of high interfacial activity. The viscoelastic response of the system is rationalized by the presence of a superstable structured dual network. When used as a templating material, the emulgel develops into structured liquids and cryogels. The herein introduced all-biobased type of nanoparticle surfactant system forms a gel ("emulsion-filled" with "aggregated droplets") that features the functional benefits of both betulin and nanochitin.

Development of Emulsion Gels Stabilized by Chitosan and Octenyl Succinic Anhydride-Modified β-Cyclodextrin Complexes for β-Carotene Digestion and 3D Printing

β-cyclodextrin (β-CD)-based emulsion gels encapsulated with nutrition for three-dimensional (3D) printing are promising, while obstacles such as low bioaccessibility of bioactive compounds and the molding process in food manufacturing hinder their application. This study intended to develop stable composite emulsion gels using the complexes of chitosan (CS) and octenyl succinic anhydride (OSA)-modified β-CD (OCD) to conquer these challenges. The esterification of OSA generated more negatively charged OCD and ester groups, which aided in the combination of OCD and CS through enhanced electrostatic and hydrogen bonding interactions. The addition of CS improved the emulsification properties of the complexes and acted as a bridge link in the aqueous phase, thereby increasing the gel strength of the composite emulsion gels. Moreover, the encapsulation of β-carotene destabilized the strength of the emulsion gels by lowering the interfacial tension. The emulsion gel stabilized by OCD3/CS-0.75% at an initial pH not only successfully encapsulated β-carotene and presented the highest bioaccessibility of 41.88 ± 0.87% in the in vitro digestion but also showed excellent 3D printability. These results provided a promising strategy to enhance the viscoelasticity of β-CD-based emulsion gels and accelerate their application in bioactive compound delivery systems and 3D food printing.

Saltiness perception in gel-based food systems (gels and emulsion-filled gels)

Reducing salt in food without compromising its quality is a huge challenge. Some review articles have been recently published on saltiness perception in some colloidal systems such as emulsions. However, no published reviews are available on saltiness perceptions of gel-based matrices, even though salt release and perception in these systems have been extensively studied. This article reviews the recent advances in salt perception in gel-based systems and provides a detailed analysis of the main factors affecting salt release. Strategies to enhance saltiness perception in gels and emulsion-filled gels are also reviewed. Saltiness perception can be improved through addition of biopolymers (proteins and polysaccharides) due to their ability to modulate texture and/or to adhere to or penetrate through the mucosal membrane on the tongue to prolong sodium retention. The composition of the product and the distribution of salt within the matrix are the two main factors affecting the perception of salty taste. Food structure re-design can lead to control the level of interaction between the salt and other components and change the structure, which in turn affects the mobility and release of the salt. The change of ingredients/matrix can affect the texture of the product, highlighting the importance of sensory evaluation.

High-Performance Nanogel-in-Oils as Emulsion Evolution Controller for Displacement Enhancement in Porous Media

We designed and synthesized high-performance nanogel-in-oils with intermediate properties between solid particles and liquid droplets for multiphase flow control in porous media. The ultrasmall polymeric nanogels prepared via inverse emulsion polymerization were efficiently encapsulated in micrometer-sized oil droplets with the aid of surfactants during transfer from the oil phase to the aqueous phase. The composite colloidal system exhibited high loading capacity, unimodal size distribution, and long-term kinetic stability in suspension. The colloidal behaviors of nanogel-in-oils and the corresponding interfacial evolution during displacement in porous media were investigated via microfluidic experiments. In situ emulsification was observed with a state contrary to that of static characterizations. The spontaneous and sustainable formation of foam-like water-in-oil macroemulsions originated from aqueous phase breakup and oil film development, both enhanced by nanogel-in-oils. Sweeping efficiency enhancement by invasion events and residual oil transport in macroemulsion phases yielded exceptional displacement performances. Flow field fluctuations and emulsion state variations can be manipulated by adjusting nanogel-in-oil concentrations. The nanogel-in-oil suspension was found to exhibit optimal performance among the tested dispersed systems.

Transglutaminase, glucono-δ-lactone, and citric acid-induced whey protein isolation-milk fat emulsion gel embedding lutein and its application in processed cheese

In this study, transglutaminase (TG), glucono-δ-lactone (GDL), and citric acid (CA) were used to induce the formation of whey protein isolate (WPI)-milk fat emulsion gels to embed lutein, and the emulsion gels induced in different ways were used for the preparation of processed cheese. The protective effect of emulsion gels induced in different ways on lutein was investigated, and the stability of lutein in emulsion gels and processed cheese was analyzed. The results showed that the acidification rate of CA was higher than that of GDL, which was the key step in acid-induced gels, and that the difference in acidification rate led to differences in gel structure. Compared with the 2 acid inducers (GDL and CA), TG exhibited greater potential for forming gel structures with high strength. The TG-induced emulsion gels showed the best physical stability and the highest embedding efficiency for lutein. After heat treatment (85°C), the GDL-induced emulsion gels had higher retention rate of lutein and showed good thermal stability compared with the CA-induced emulsion gels. The processed cheese added with the TG-induced emulsion gel had higher hardness and springiness compared with the processed cheese added with the other 2 kinds of emulsion gels, whereas the processed cheese added with the CA-induced emulsion gel had a lower density of network structure, showing porosity and a larger aggregated structure, but the highest bioavailability of lutein. These results provide valuable information for the formation of cold-set emulsion gel and provide the possibility for the application of emulsion gel embedding active substances in processed cheese.

Synthetic and biopolymeric microgels: Review of similarities and difference in behaviour in bulk phases and at interfaces

This review discusses the current knowledge of interfacial and bulk interactions of biopolymeric microgels in relation to the well-established properties of synthetic microgels for applications as viscosity modifiers and Pickering stabilisers. We present a timeline showing the key milestones in designing microgels and their bulk/ interfacial performance. Poly(N-isopropylacrylamide) (pNIPAM) microgels have remained as the protagonist in the synthetic microgel domain whilst proteins or polysaccharides have been primarily used to fabricate biopolymeric microgels. Bulk properties of microgel dispersions are dominated by the volume fraction (ϕ) of the microgel particles, but ϕ is difficult to pinpoint, as addressed by many theoretical models. By evaluating recent experimental studies over the last five years, we find an increasing focus on the analysis of microgel elasticity as a key parameter in modulating their packing at the interfaces, within the provinces of both synthetic and biopolymeric systems. Production methods and physiochemical factors shown to influence microgel swelling in the aqueous phase can have a significant impact on their bulk as well as interfacial performance. Compared to synthetic microgels, biopolymer microgels show a greater tendency for polydispersity and aggregation and do not appear to have a core-corona structure. Comprehensive studies of biopolymeric microgels are still lacking, for example, to accurately determine their inter- and intra- particle interactions, whilst a wider variety of techniques need to be applied in order to allow comparisons to real systems of practical usage.

Food gel-based systems for efficient delivery of bioactive ingredients: design to application

Food gels derived from natural biopolymers are valuable materials with significant scientific merit in the food industry because of their biocompatibility, safety, and environmental friendliness compared to synthetic gels. These gels serve as crucial delivery systems for bioactive ingredients. This review focuses on the selection, formulation, characterization, and behavior in gastrointestinal of hydrogels, oleogels, and bigels as delivery systems for bioactive ingredients. These three gel delivery systems exhibit certain differences in composition and can achieve the delivery of different bioactive ingredients. Hydrogels are suitable for delivering hydrophilic ingredients. Oleogels are an excellent choice for delivering lipophilic ingredients. Bigels contain both aqueous and oil phases, whose gelation makes their structure more stable, demonstrating the advantages of the above two types of gels. Besides, the formation and properties of the gel system are confirmed using different characterization methods. Furthermore, the changing behavior (e.g., swelling, disintegration, collapse, erosion) of the gel structure in the gastrointestinal is also analyzed, providing an opportunity to formulate soft substances that offer better protection or controlled release of bioactive components. This can further improve the transmissibility and utilization of bioactive substances, which is of great significance.

Application of guar (Cyamopsis tetragonoloba L.) gum in food technologies: A review of properties and mechanisms of action

With the world continuing to push toward modernization and the consumption of processed foods growing at an exponential rate, the demand for texturizing agents and natural additives has also risen as a result. It has become increasingly common to use thickening agents in food products to modify their rheological and textural properties and enhance their quality characteristics. They can be divided into (1) animal derived (chitosan and isinglass), (2) fermentation produced (xanthan and curdlan), (3) plant fragments (pectin and cellulose), (4) seaweed extracts (agar and alginate), and (5) seed flours (guar gum and locust bean gum). The primary functions of these materials are to improve moisture binding capacity, modify structural properties, and alter flow behavior. In addition, some have another responsibility in the food sector, such as the main ingredient in the delivery systems (encapsulation) and nanocomposites. A galactomannan polysaccharide extracted from guar beans (Cyamopsis tetragonolobus), known as guar gum (GG), is one of them, which has a wide range of utilities and possesses popularity among scientists and consumers. In the world of modernization, GG has found its way into numerous industries for use in food, cosmetics, pharmaceuticals, textiles, and explosives. Due to its ability to form hydrogen bonds with water molecules, it imparts significant thickening, gelling, and binding properties to the solution as well as increases its viscosity. Therefore, this study is aimed to investigate the characteristics, mechanisms, and applications of GG in different food technologies.

In Vitro Bioaccessibility Assessment of Phenolic Compounds from Encapsulated Grape Pomace Extract by Ionic Gelation

Grape pomace is a by-product of winemaking characterized by a rich chemical composition from which phenolics stand out. Phenolics are health-promoting agents, and their beneficial effects depend on their bioaccessibility, which is influenced by gastrointestinal digestion. The effect of encapsulating phenol-rich grape pomace extract (PRE) with sodium alginate (SA), a mixture of SA with gelatin (SA-GEL), and SA with chitosan (SA-CHIT) on the bioaccessibility index (BI) of phenolics during simulated digestion in vitro was studied. A total of 27 individual phenolic compounds (IPCs) were quantified by UHPLC. The addition of a second coating to SA improved the encapsulation efficiency (EE), and the highest EE was obtained for SA-CHIT microbeads (56.25%). Encapsulation affected the physicochemical properties (size, shape and texture, morphology, crystallinity) of the produced microbeads, which influenced the delivery of phenolics to the intestine and their BI. Thus, SA-GEL microbeads had the largest size parameters, as confirmed by scanning electron microscopy (SEM), and the highest BI for total phenolic compounds and IPCs (gallic acid, 3,4-dihydroxybenzoic acid and o-coumaric acid, epicatechin, and gallocatechin gallate) ranged from 96.20 to 1011.3%. The results suggest that encapsulated PRE has great potential to be used as a functional ingredient in products for oral administration.

Constitution and reconstitution of microcapsules with high diacylglycerol oil loading capacity based on whey protein isolate / octenyl succinic anhydride starch/ inulin matrix

The aim of this study was to constitute microcapsule systems with high oil loading capacity by octenyl succinic anhydride (OSA) starch, whey protein isolate (WPI) and inulin (IN) substrates to provide a new method for encapsulating diacylglycerol oil. Specifically, this study characterizes the physicochemical properties and reconstitution capacity of highly oil loading diacylglycerol microcapsules by comparing the wall encapsulation capacity of the binary wall system OSA-IN, WPI-IN and the ternary wall system WPI-OSA (1:9, 5:5, 9:1)-IN for diacylglycerol oil. It was found that WPI-OSA (5:5)-IN significantly improved the water solubility of microcapsules (86.11 %) compared to OSA-IN microcapsules, and the addition of WPI made the surface of microcapsules smoother and increased the thermal stability and solubility of microcapsules; the addition of OSA enhanced the wettability of microcapsules compared to WPI-IN. In addition, WPI-OSA (5:5)-IN microcapsules have the highest encapsulation efficiency (96.03 %), high emulsion stability after reconstitution, and the smallest droplet size (212.83 nm) after 28 d. Therefore, the WPI-OSA-IN composite system is suitable for the production of highly oil-loaded microencapsulated systems with excellent reconstitution ability to expand the application of diacylglycerol oil.

Development of engineered probiotics with tailored functional properties and their application in food science

The potential health benefits of probiotics may not be cognized because of the substantial curtailment in their viability during food storage and passage through the gastrointestinal system. Intestinal flora composition, and resistance against pathogens are among the health benefits associated with probiotic consumption. In the gastric environment, pH 2.0, probiotics dramatically lose their viability during the transit through the gastrointestinal system. The challenge remains to maintain cell viability until it reaches the large intestine. In extreme conditions, such as a decrease in pH or an increase in temperature, encapsulation technology can enhance the viability of probiotics. Probiotic bacterial strains can be encapsulated in a variety of ways. The methods are broadly systematized into two categories, liquid and solid delivery systems. This review emphasizes the technology used in the research and commercial sectors to encapsulate probiotic cells while keeping them alive and the food matrix used to deliver these cells to consumers.

Graphical abstract

OSA-starch stabilized EPA nanoliposomes: preparation, characterization, stability and digestion in vitro and in vivo

OSA-starch stabilized EPA nanoliposomes (OSA-EPA-NLs) were prepared by thin film rehydration/dispersion method. The physical properties and morphology of OSA-EPA-NLs were characterized. The best formulated sample was used to measure the storage stability and oxidative properties of EPA under different environmental stresses and to determine release and absorption of OSA-EPA-NLs in vitro and in vivo. The results showed that the encapsulation efficiency of OSA-EPA-NLs was 84.61%. All samples were relatively stable under different environmental stresses, and the release rate of EPA in simulated intestine stage (89.87%) was higher than that in the simulated gastric stage (5.86%). The areas under the EPA concentration-time curve of OSA-EPA-NLs group and EPA-NLs group through in vivo study were 0.42 and 0.32, respectively, which indicated that OSA-starch could improve the stability of EPA nanoliposomes and enhance EPA bioavailability in the form of ethyl esters.

Recent progress in emulsion gels: from fundamentals to applications

Emulsion gels, also known as gelled emulsions or emulgels, have garnered great attention both in fundamental research and practical applications due to their superior stability, tunable morphology and microstructure, and promising mechanical and functional properties. From an application perspective, attention in this area has been, historically, mainly focused on food industries, e.g., engineering emulsion gels as fat substitutes or delivery systems for bioactive food ingredients. However, a growing body of studies has, in recent years, begun to demonstrate the full potential of emulsion gels as soft templates for designing advanced functional materials widely applied in a variety of fields, spanning chemical engineering, pharmaceutics, and materials science. Herein, a concise and comprehensive overview of emulsion gels is presented, from fundamentals to applications, highlighting significant recent progress and open questions, to scout for and deepen their potential applications in more fields.

Design of glucono-δ-lactone-induced pinto bean protein isolate/κ-carrageenan mixed gels with various microstructures: fabrication, characterization, and release behavior

BACKGROUND

Protein gels are used for different purposes, such as providing good texture, serving as fat replacers, and enhancing the nutritional and functional characteristics of foods. They can also deliver controlled release agents for sensitive drugs. The objective of this study was to investigate the impact of κ-carrageenan (kcr) concentration (0, 1.5, 3, and 4.5 mg g^-1 ) on the morphological and physicochemical properties and release behavior of glucono-δ-lactone (GDL)-induced pinto bean protein aggregate (PBA) gels.

RESULTS

When κ-carrageenan concentration increased from 0 to 1.5 and 3 mg.g^-1 , the firmness of the samples increased significantly, by 2.04 and 3.7 fold, respectively (P < 0.05). A compact and homogenous network with considerable strength and maximum water-holding capacity (97.52 ± 1.17%) was obtained with the addition of 3 mg g^-1 κ-carrageenan to the gel system. Further increasing the κ-carrageenan concentration to 4.5 mg g^-1 produced a coarse gel structure with higher storage modulus (G'), firmness (6.30-fold), thermal stability, and entrapment efficiency (85.6%). Depending on the κ-carrageenan concentration, various microstructures from protein continuous phase to κ-carrageenan continuous phase were observed. The release test indicated that 70.25% of the loaded curcumin was released in the simulated gastrointestinal tract for pure PBA gels. In contrast, for binary gels containing 4.5 mg g^-1 κ-carrageenan, curcumin was protected in the upper gastrointestinal tract, and 64.45% of loaded curcumin was delivered to the colon.

CONCLUSION

Our study showed that κ-carrageenan/PBA gels had high entrapment efficiency and could protect curcumin in the upper gastrointestinal tract. The hydrogels are therefore very valuable for colon-targeting delivery purposes. © 2022 Society of Chemical Industry.

Producing mixed-soy protein adsorption layers on alginate microgels to controlled-release β-carotene

In this study, the effects of soy protein isolate (SPI) on the morphology, encapsulation efficiency, storage stability, swelling behavior, and in vitro digestion behavior of calcium alginate (CA) microgels were investigated. CA and calcium alginate-SPI (CAS) microgels with encapsulated β-carotene were prepared by extruding a mixture of alginate and SPI using a co-extrusion technique, followed by cross-linking with Ca²⁺. All microgels exhibited homogeneous sizes and spherical shapes, and CAS microgels showed high levels of protein loading efficiency. The encapsulation efficiency and storage stability of β-carotene within CAS microgels were higher than those within CA microgels. The introduction of SPI into CAS microgels resulted in a higher degree of gel size shrinkage in gastric fluid and a lower degree of swelling in intestinal fluid compared to CA microgels. In vitro digestion was conducted to investigate the effects of the addition of SPI on the release behavior of CA and CAS microgels. Results obtained showed that CAS microgels were more resistant to simulated gastric fluid than CA microgels. Cryo-scanning electron microscopy (cryo-SEM) and confocal laser scanning microscopy (CLSM) observations indicated that the release behavior was dependent on the porosity of the CA and CAS microgels, and the porosity was influenced by the concentration of SPI. This study showed that the introduction of SPI to CA microgels can lead to the development of an effective controlled release delivery system.

Recent advances in cellulose microgels: Preparations and functionalized applications

Microgels are soft, deformable, permeable, and stimuli-responsive microscopic polymeric particles that are now emerging as prospective multifunctional soft materials for delivery systems, interface stabilization, cell cultures and tissue engineering. Cellulose microgels are emerging biopolymeric microgels with unique characteristics such as abound hydroxyl structure, admirable designability, multiscale pore network and excellent biocompatibility. This review summarizes the fabrication strategies for microgel, then highlights the fabrication routes for cellulose microgels, and finally elaborates cellulose microgels' bright application prospects with unique characteristics in the fields of controlled release, interface stabilization, coating, purification, nutrition/drug delivery, and bio-fabrication. The challenges to be addressed for further applications and considerable scope for development in future of cellulose microgels are also discussed.

Multiphase displacement manipulated by micro/nanoparticle suspensions in porous media via microfluidic experiments: From interface science to multiphase flow patterns

Multiphase displacement in porous media can be adjusted by micro/nanoparticle suspensions, which is widespread in many scientific and industrial contexts. Direct visualization of suspension flow dynamics and corresponding multiphase patterns is crucial to understanding displacement mechanisms and eventually optimizing these processes in geological, biological, chemical, and other engineering systems. However, suspension flow inside the opaque realistic porous media makes direct observation challenging. The advances in microfluidic experiments have provided us with alternative methods to observe suspension influence on the interface and multiphase flow behaviors at high temporal and spatial resolutions. Macroscale processes are controlled by microscale interfacial behaviors, which are affected by multiple physical factors, such as particle adsorption, capillarity, and hydrodynamics. These properties exerted on the suspension flow in porous media may lead to interesting interfacial phenomena and new displacement consequences. As an underpinning science, understanding and controlling the suspension transport process from interface to flow patterns in porous media is critical for a lower operating cost to improve resource production while reducing harmful emissions and other environmental impacts. This review summarizes the basic properties of different micro/nanoparticle suspensions and the state-of-the-art microfluidic techniques for displacement research activities in porous media. Various suspension transport behaviors and displacement mechanisms explored by microfluidic experiments are comprehensively reviewed. This review is expected to boost both experimental and theoretical understanding of suspension transport and interfacial interaction processes in porous media. It also brings forward the challenges and opportunities for future research in controlling complex fluid flow in porous media for diverse applications.

Effect of ultrasonic pretreatment on the rheology and structure of grass pea (Lathyrus sativus L.) protein emulsion gels induced by transglutaminase

In this study, emulsion gels were prepared by sonicated grass pea protein isolates (GPPI) at different ultrasonic amplitudes (25, 50 and 75 %) and times (5, 10 and 20 min). Formation of emulsion gels was induced by transglutaminase. Enzymatic gelation of emulsions stabilized by sonicated GPPI occurred in two stages. A relatively fast stage led to the formation of a weak gel which was followed by a slow stage that strongly reinforced the gel structure. Emulsion gels fabricated by sonicated GPPIs showed a homogeneous and uniform droplet distribution with higher elastic modulus compared to the native protein. A stiffer emulsion gel with a higher G' was formed after the protein was treated at 75 % amplitude for 10 min. After sonication of GPPI, the water holding capacity (WHC) of emulsion gels increased in accordance with the mechanical properties. Higher intermolecular cross-linking within the gel network increased the thermal stability of emulsion gels fabricated by sonicated GPPI. Although sonicated-GPPI emulsion gels clearly displayed homogenous microstructure in comparison to that made with native GPPI, the microstructures of these gels were nearly identical for all sonication amplitudes and times.

The Improvement of Dispersion Stability and Bioaccessibility of Calcium Carbonate by Solid/Oil/Water (S/O/W) Emulsion

Solid/oil/water (S/O/W) emulsion loaded with calcium carbonate (CaCO₃) was constructed to raise the dispersion stability and bioaccessibility. In the presence or absence of sodium caseinate (NaCas), the particle size, Zeta-potential, physical stability, and apparent viscosity of stabilized S/O/W emulsions with different gelatin (GEL) concentrations (0.1~8.0 wt%) were compared. Combined with a confocal laser scanning microscope (CLSM), cryoscanning electron microscope (Cryo-SEM), and interfacial adsorption characteristics, the stabilization mechanism was analyzed. The bioavailability of CaCO₃ was investigated in a simulated gastrointestinal tract (GIT) model. The S/O/W-emulsion droplets prepared by the NaCas-GEL composite have a smaller particle size, higher Zeta-potential, larger apparent viscosity, and better physical stability compared with GEL as a single emulsifier. CLSM results confirmed that CaCO₃ powder was encapsulated in emulsion droplets. The Cryo-SEM results and interfacial adsorption characteristics analysis indicated that the NaCas-GEL binary composite could effectively reduce the interfacial tension, and the droplets form a denser three-dimensional network space structure with a shell-core structure which enhanced the stability of the system. GIT studies showed that the droplets presented higher CaCO₃ bioaccessibility than the CaCO₃ powder. This study enriched the theory of the S/O/W transfer system and provided theoretical support for the development of CaCO₃ application in liquid food.

Stability, Structure, Rheological Properties, and Tribology of Flaxseed Gum Filled with Rice Bran Oil Bodies

In this study, rice bran oil bodies (RBOBs) were filled with varying concentrations of flaxseed gum (FG) to construct an RBOB-FG emulsion-filled gel system. The particle size distribution, zeta potential, physical stability, and microstructure were measured and observed. The molecular interaction of RBOBs and FG was studied by Fourier transform infrared spectroscopy (FTIR). In addition, the rheological and the tribology properties of the RBOB-FG emulsion-filled gels were evaluated. We found that the dispersibility and stability of the RBOB droplets was improved by FG hydrogel, and the electrostatic repulsion of the system was enhanced. FTIR analysis indicated that the hydrogen bonds and intermolecular forces were the major driving forces in the formation of RBOB-FG emulsion-filled gel. An emulsion-filled gel-like structure was formed, which further improved the rheological properties, with increased firmness, storage modulus values, and viscoelasticity, forming thermally stable networks. In the tribological test, with increased FG concentration, the friction coefficient (μ) decreased. The elasticity of RBOB-FG emulsion-filled gels and the ball-bearing effect led to a minimum boundary friction coefficient (μ). These results might contribute to the development of oil-body-based functional ingredients for applications in plant-based foods as fat replacements and delivery systems.

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.

Construction of lipid-biomacromolecular compounds for loading and delivery of carotenoids: Preparation methods, structural properties, and absorption-enhancing mechanisms

Due to the unstable chemical properties and poor water solubility of carotenoids, their processing adaptation and oral bioavailability are poor, limiting their application in hydrophilic food systems. Lipid-biomacromolecular compounds can be excellent carriers for carotenoid delivery by taking full advantage of the solubilization of lipids to non-polar nutrients and the water dispersion and gastrointestinal controlled release properties of biomacromolecules. This paper reviewed the research progress of lipid-biomacromolecular compounds as encapsulation and delivery carriers of carotenoids and summarized the material selection and preparation methods for biomacromolecular compounds. By considering the interaction between the two, this paper briefly discussed the effect of these compounds on carotenoid water solubility, stability, and bioavailability, emphasizing their delivery effect on carotenoids. Finally, various challenges and future trends of lipid-biomacromolecular compounds as carotenoid delivery carriers were discussed, providing new insight into efficient loading and delivery of carotenoids.

Docosahexaenoic Acid Delivery Systems, Bioavailability, Functionality, and Applications: A Review

Docosahexaenoic acid (DHA), mainly found in microalgae and fish oil, is crucial for the growth and development of visual, neurological, and brain. In addition, DHA has been found to improve metabolic disorders associated with obesity and has anti-inflammatory, anti-obesity, and anti-adipogenesis effects. However, DHA applications in food are often limited due to its low water solubility, instability, and poor bioavailability. Therefore, delivery systems have been developed to enhance the remainder of DHA activity and increase DHA homeostasis and bioavailability. This review focused on the different DHA delivery systems and the in vitro and in vivo digestive characteristics. The research progress on cardiovascular diseases, diabetes, visual, neurological/brain, anti-obesity, anti-inflammatory, food applications, future trends, and the development potential of DHA delivery systems were also reviewed. DHA delivery systems could overcome the instability of DHA in gastrointestinal digestion, improve the bioavailability of DHA, and better play the role of its functionality.

CaCO3 loaded lipid microspheres prepared by the solid-in-oil-in-water emulsions technique with propylene glycol alginate and xanthan gum

Calcium carbonate (CaCO3) is difficult to deliver in food matrices due to its poor solubility. In this work, CaCO3 powders were encapsulated into Solid-in-Oil-in-Water (S/O/W) emulsions to fabricate delivery systems. The impact of the concentrations of propylene glycol alginate and Xanthan gum (PGA-XG) complexes on the physical stability and structural characteristics of S/O/W calcium-lipid emulsions microspheres were studied. The S/O/W calcium-lipid emulsions were characterized by the particle size, zeta potential, physical stability, and apparent viscosity. The S/O/W calcium-lipid emulsion has higher physical stability (including 6-week storage at 4°C), smaller mean particle size (7.60 ± 1.10 μm), and higher negative zeta-potential (45.91 ± 0.97 mV) when the concentration of PGA-XG complexes was 0.8 wt%. Moreover, Confocal laser scanning microscopy (CLSM) images confirmed that the CaCO3 powders were encapsulated in the O phase. Transmission electron microscopy (TEM) showed that S/O/W calcium-lipid emulsion was spherical. The X-ray diffraction (XRD) analysis further confirmed that CaCO3 was loaded in the S/O/W calcium-lipid emulsion as an amorphous state. The formation mechanism of S/O/W calcium-lipid microspheres was studied by Fourier transform infrared spectroscopy (FTIR) and Raman spectrum analysis. This study provided new ideas that accelerate the creation of a novel type of calcium preparation with higher quality utilization.

High-performance displacement by microgel-in-oil suspension in heterogeneous porous media: Microscale visualization and quantification

HYPOTHESIS

Preferential flow in porous media is commonly encountered and decreases the multiphase displacement efficiency. Here, we synthesized microgel-in-oil in suspension and demonstrated that microgel-in-oil as a novel additive could present self-adaptive transport behavior and introduce a novel multiphase displacement mode for improving displacement efficiency in heterogeneous porous media.

EXPERIMENTS

We investigated the microgel-in-oil formation process and characterized their morphology with fluorescence microscopy and Cryo-SEM. The suspension displacement performance in heterogeneous porous media was evaluated using a microfluidic chip containing a preferential flow pathway (PFP) and a parallel matrix region. The displacement results of microgel-in-oil were compared to plain microgel particles and analyzed from pore-scale particle transport behavior to macroscopic multiphase flow patterns.

FINDINGS

The results show that suspension with moderate microgel-in-oil yields the optimal displacement efficiency. Fewer microgel-in-oil cannot alter the flow direction, while too many microgel-in-oil would block the PFP region. The topological analysis identified that suspensions with moderate microgel-in-oil content could achieve the strongest sweeping and carrying abilities that contribute to the highest displacement efficiency. The synergistic transport of microgel-in-oil and plain microgel particles would result in local pressure fluctuations to divert displacing fluid from PFP into the matrix region, which explains the above flow behavior.

Are quinoa proteins a promising alternative to be applied in plant-based emulsion gel formulation?

Emulsion gels are structured emulsion systems that behave as soft solid-like materials. Emulsion gels are commonly used in food-product design both as fat replacers and as delivery carriers of bioactive compounds. Different plant-derived proteins like soy, chia, and oat have been used in emulsion gel formulation to substitute fat in meat products and to deliver some vegetable dyes or extracts. Quinoa protein isolates have been scarcely applied in emulsion gel formulation although they seem to be a promising alternative as emulsion stabilizers. Quinoa protein isolates have a high protein content with a well-balanced amino acid profile and show good emulsifying and gelling capabilities. Unlike quinoa starch, quinoa protein isolates do not require any chemical modification before being used. The present article reviews the state of the art in food emulsion gels stabilized with vegetable proteins and highlights the potential uses of quinoa proteins in emulsion gel formulation.