Effects of inducer type and concentration on the formation mechanism of W/O/W double emulsion gels

Improvement of physicochemical properties and quercetin delivery ability of fermentation-induced soy protein isolate emulsion gel processed by ultrasound

This study aimed to investigate the effects of ultrasonic treatment at different powers on the physicochemical properties, microstructure and quercetin delivery capacity of fermentation-induced soy protein isolate emulsion gel (FSEG). The FSEG was prepared by subjecting soy protein isolate (SPI) emulsion to ultrasonic treatment at various powers (0, 100, 200, 300, and 400 W), followed by lactic acid bacteria fermentation. Compared with the control group (0 W), the FSEG treated with ultrasound had higher hardness, water holding capacity (WHC) and rheological parameters. Particularly, at an ultrasonic power of 300 W, the FSEG had the highest hardness (101.69 ± 4.67 g) and WHC (75.20 ± 1.07%) (p < 0.05). Analysis of frequency sweep and strain scanning revealed that the storage modulus (G') and yield strains of FSEG increased after 300 W ultrasonic treatment. Additionally, the recovery rate after creep recovery test significantly increased from 18.70 ± 0.49% (0 W) to 58.05 ± 0.54% (300 W) (p < 0.05). Ultrasound treatment also resulted in an increased β-sheet content and the formation of a more compact micro-network structure. This led to a more uniform distribution of oil droplets and reduced mobility of water within the gel. Moreover, ultrasonic treatment significantly enhanced the encapsulation efficiency of quercetin in FSEG from 81.25 ± 0.62 % (0 W) to 90.04 ± 1.54% (300 W). The bioaccessibility of quercetin also increased significantly from 28.90 ± 0.40% (0 W) to 42.58 ± 1.60% (300 W) (p < 0.05). This study enriches the induction method of soy protein emulsion gels and provides some references for the preparation of fermented emulsion gels loaded with active substances.

Fabrication and Stability Improvement of Monoglyceride Oleogel/Polyglycerol Polyricinoleate-Stabilized W/O High Internal Phase Pickering Emulsions

To decrease the lipid content in water-in-oil (W/O) emulsions, high internal phase Pickering W/O emulsions (HIPPE) were fabricated using magnetic stirring using a combination of monoglyceride (MAG) oleogel and polyglycerol polyacrylate oleate (PGPR) as stabilizers. Effects of MAGs (glyceryl monostearate-GMS, glycerol monolaurate-GML and glycerol monocaprylate-GMC) and internal phase components on the formation and properties of HIPPEs were investigated. The results showed that milky-white stabilized W/O HIPPE with up to 85 wt% aqueous phase content was successfully prepared, and the droplet interfaces presented a network of MAG crystals, independent of the MAG type. All HIPPEs exhibited great stability under freeze-thaw cycles but were less plastic. Meanwhile, GML-oleogel-based HIPPEs had larger particle size and were less thermal stable than GMS and GMC-based HIPPEs. Compared to guar gum, the internal phase components of sodium chloride and sucrose were more effective in reducing the particle size of HIPPEs, improving their stability and plasticity, and stabilizing them during 100-day storage. HIPPEs presented great spreadability, ductility and plasticity after whipping treatment. This knowledge provides a new perspective on the use of oleogels as co-stabilizers for the formation of W/O HIPPEs, which can be used as a potential substitute for creams.

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.

O1/W/O2 double emulsion gels based on nanoemulsions and Pickering particles for co-encapsulating quercetin and cyanidin: A functional fat substitute

An O1/W/O2 double emulsion gel, as a functional fat substitute and based on nanoemulsions and hydrophobic Pickering particles, is prepared by two-step emulsification to co-encapsulate hydrophilic cyanidin and hydrophobic quercetin. Nanoemulsions loading quercetin are fabricated by Tween-80 and combining high-speed and high-pressure emulsification. Phytosterol nanoparticles stabilize the W-O2 interface of the secondary emulsion to load cyanidin in the W phase. The concentration of Tween-80 is optimized as 0.3% by the droplet size and viscosity of nanoemulsions. The structural stability of double emulsion gels will be weakened along with the increase of nanoemulsions, showing lower modulus and encapsulation efficiency (EE) and bigger droplets. In double emulsion gels, the EE of quercetin and cyanidin reaches 93% and 85.6%, respectively. Analysis of molecular interaction indicates that Tween-80 would decrease the in-situ hydrophobicity of phytosterol nanoparticles by hydrogen bonding adsorption, thereby weakening the emulsification. The pH-chromic 3D printing of double emulsion gels is designed according to the pH sensitivity of cyanidin. Texture profile analysis is performed to test the textural properties of 3D-printed objects. The simulated digestion is conducted on double emulsion gels. The double emulsion gel with fewer nanoemulsions is beneficial for protecting quercetin and improving the delivery due to the higher structural stability, while that with more nanoemulsions is conducive to the digestion of cyanidin and camellia oil due to weakened semi-solid properties. This double emulsion gel further simulates fat tissues by co-encapsulating hydrophilic and hydrophobic substances, promoting the application of fat substitutes in the food industry.

An Updated Comprehensive Overview of Different Food Applications of W1/O/W2 and O1/W/O2 Double Emulsions

Double emulsions (DEs) present promising applications as alternatives to conventional emulsions in the pharmaceutical, cosmetic, and food industries. However, most review articles have focused on the formulation, preparation approaches, physical stability, and release profile of encapsulants based on DEs, particularly water-in-oil-in-water (W1/O/W2), with less attention paid to specific food applications. Therefore, this review offers updated detailed research advances in potential food applications of both W1/O/W2 and oil-in-water-in-oil (O1/W/O2) DEs over the past decade. To this end, various food-relevant applications of DEs in the fortification; preservation (antioxidant and antimicrobial targets); encapsulation of enzymes; delivery and protection of probiotics; color stability; the masking of unpleasant tastes and odors; the development of healthy foods with low levels of fat, sugar, and salt; and design of novel edible packaging are discussed and their functional properties and release characteristics during storage and digestion are highlighted.

Co-encapsulation of collagen peptide and astaxanthin in WG/OG/W double emulsions-filled alginate hydrogel beads: Fabrication, characterization and digestion behaviors

The double emulsions-filled hydrogel beads delivery systems with controlled lipolysis and sustained-release property of co-encapsulated bioactive substances will be highly desired. Herein, the water-in-oil-in-water emulsion with gelled inner water phase and oil phase (WG/OG/W) filled hydrogel beads as a novel co-delivery system were developed with varied concentrations of rice bran wax and W/O emulsions to achieve effectively controlled release of lipolysis and nutraceuticals. Interestingly, the gelation of oil phase triggered by rice bran wax could enhance the storage stability of WG/OG/W emulsions due to the enhanced viscoelastic property. Increasing the mass fractions of W/O emulsions improved the stability of double emulsions due to increased viscosity and decreased particle size. Cryo-SEM observation showed that the double emulsion droplets were scattered in the three-dimensional network of alginate gel beads. Increased the addition of rice bran wax or W/O emulsions, the encapsulation efficiency of collagen peptide and astaxanthin was significantly improved. The in vitro digestion results indicated that increasing the concentrations of rice bran wax and W/O emulsion fractions in WG/OG/W emulsion-filled gel beads could effectively delay the release extent of free fatty acids and encapsulated nutraceuticals. The presence of rice bran wax contributed to increase the bioaccessibility of collagen peptide and astaxanthin.

The structural and functional properties of soybean protein-polyglutamic acid complex effected the stability of W/O/W emulsion encapsulated Nattokinase

Nattokinase (NK) derived from food is a sustainable thrombolytic agent. In this study, to protect vulnerable biological activity of NK, the targeted modified W/O/W emulsions were fabricated from complexes of soybean isolate protein (SPI) and polyglutamic acid (PGA). The results showed that the SPI-PGA complex formed a tighter internal structure through non-covalent bonds. The secondary structure, α-helix and β-sheet content of the 1:3 (v/v) ratio complex of SPI to PGA increased by 6.14% and 8.62%, respectively. The emulsification and stability of the complexes were improved by refining structural properties as against SPI. The W/O/W emulsions coated by complexes formed the stronger network structure with higher encapsulation efficiency, better interfacial features, and better storage stability. Moreover, the highest bioavailability was achieved by W/O/W emulsions coated with 1:3 ratio complex at 80.69%. This study provided a new strategy towards tailoring ideal emulsion vehicles and expanded the NK application in food formulations.

Fabrication of anthocyanin–rich W1/O/W2 emulsion gels based on pectin–GDL complexes: 3D printing performance

The stability of anthocyanin-rich W₁/O/W₂ double emulsions prepared with Nicandra physalodes (Linn.) Gaertn. Seeds pectin was investigated, including droplet sizes, ζ-potential, viscosity, color, microstructures and encapsulation efficiency. Furthermore, the gelation behavior, rheological behavior, texture behavior and three-dimensional (3D) printing effects of the W₁/O/W₂ emulsion gels induced with Glucono-delta-lactone (GDL) were studied. The L*, b*, ΔE, droplet sizes and ζ-potential of the emulsions were gradually increased, while other indicators were gradually decreased during 28 days of storage under 4 ℃. The storage stability of sample under storage at 4 ℃ was higher than 25 ℃. The G' of W₁/O/W₂ emulsion gels gradually boosted with increased GDL addition, and reached the highest after the addition of 1.6 % GDL. In creep-recovery sweep, the minimum strain of 1.68 % and the highest recovery rate of 86 % were also found for the emulsion gels with 1.6 % GDL. Accordingly, the models "KUST", hearts, flowers printed by emulsion gels after 60 min addition of 1.6 % GDL had the best printing effects. The W₁/O/W₂ emulsion gels based on pectin-GDL complexes exhibited good performance in protecting anthocyanins and suggested as a potential ink for food 3D printing.

Novel Colloidal Food Ingredients: Protein Complexes and Conjugates

Food proteins, polysaccharides, and polyphenols are natural ingredients with different functional attributes. For instance, many proteins are good emulsifiers and gelling agents, many polysaccharides are good thickening and stabilizing agents, and many polyphenols are good antioxidants and antimicrobials. These three kinds of ingredients can be combined into protein, polysaccharide, and/or polyphenol conjugates or complexes using covalent or noncovalent interactions to create novel multifunctional colloidal ingredients with new or improved properties. In this review, the formation, functionality, and potential applications of protein conjugates and complexes are discussed. In particular, the utilization of these colloidal ingredients to stabilize emulsions, control lipid digestion, encapsulate bioactive ingredients, modify textures, and form films is highlighted. Finally, future research needs in this area are briefly proposed. The rational design of protein complexes and conjugates may lead to the development of new functional ingredients that can be used to create more nutritious, sustainable, and healthy foods.

Effect of sodium alginate on the yogurt stability was dependent on the thickening effect and interaction between casein micelles and sodium alginate

The effect of sodium alginate (SA) on the yogurt stability and the related mechanisms were investigated. It was found that low-concentration SA (≤0.2 %) increased the yogurt stability, while high-concentration SA (≥0.3 %) decreased the yogurt stability. Sodium alginate increased the viscosity and viscoelasticity of yogurt and this effect was positively correlated with its concentration, suggesting that SA worked as the thickening agent in yogurt. However, addition of ≥0.3 % SA damaged the yogurt gel. These results suggested that interaction between milk protein and SA might play an important role in the yogurt stability besides the thickening effect. Addition of ≤0.2 % SA did not change the particle size of casein micelles. However, addition of ≥0.3 % SA induced aggregation of casein micelles and increased the size. And the aggregated casein micelles precipitated after 3 h storage. Isothermal titration calorimetry analysis showed that casein micelles and SA were thermodynamically incompatible. These results suggested that the interaction between casein micelles and SA induced aggregation and precipitation of casein micelles, which was critical in the destabilization of yogurt. In conclusion, the effect of SA on the yogurt stability was dependent on the thickening effect and the interaction between casein micelles and SA.

Engineering Emulsion Gels as Functional Colloids Emphasizing Food Applications: A Review

Gels are functional materials with well-defined structures (three-dimensional networks) assembled from the dispersed colloids, and capable of containing a large amount of water, oil, or air (by replacing the liquid within the gel pores), known as a hydrogel, oleogel, and aerogel, respectively. An emulsion gel is a gelled matrix filled with emulsion dispersion in which at least one phase, either continuous phase or dispersed phase forms spatial networks leading to the formation of a semisolid texture. Recently, the interest in the application of gels as functional colloids has attracted great attention in the food industry due to their tunable morphology and microstructure, promising physicochemical, mechanical, and functional properties, and superior stability, as well as controlled release, features for the encapsulated bioactive compounds. This article covers recent research progress on functional colloids (emulsion gels), including their fabrication, classification (protein-, polysaccharide-, and mixed emulsion gels), and properties specifically those related to the gel-body interactions (texture perception, digestion, and absorption), and industrial applications. The emerging applications, including encapsulation and controlled release, texture design and modification, fat replacement, and probiotics delivery are summarized. A summary of future perspectives to promote emulsion gels' use as functional colloids and delivery systems for scouting potential new applications in the food industry is also proposed. Emulsion gels are promising colloids being used to tailor breakdown behavior and sensory perception of food, as well as for the processing, transportation, and targeted release of food additives, functional ingredients, and bioactive substances with flexibility in designing structural and functional parameters.