Filled Hydrogel Particles Research Articles

Effects of the Incorporation of Calcium Chloride on the Physical and Oxidative Stability of Filled Hydrogel Particles.

In this study, the effects of calcium chloride (CaCl2) addition on the physical and oxidative stabilities of filled hydrogel were investigated. The results revealed that CaCl2 significantly enhanced the particle size, interfacial layer thickness, apparent viscosity, and viscoelastic behavior of filled hydrogels and decreased their light and whiteness values (p < 0.05). This phenomenon was mainly attributed to the strong binding ability between Ca2+ and protein/pectin mixtures, which were present in the interfacial area or aqueous phase, as verified by cryo-scanning electron microscopy results. Moreover, lower levels of CaCl2 (2 or 4 mM) significantly enhanced the oxidative stability of filled hydrogels (p < 0.05), particularly at a concentration of 4 mM. However, a higher level of CaCl2 (6 or 8 mM) resulted in an electrostatic shielding effect, which resulted in the aggregation of multiple droplets and the flocculation of the filled hydrogels, which negatively affected the oxidative stability of filled hydrogels. The findings of this study indicated that appropriate Ca2+ levels (4 mM) improved the physical and oxidative stability of filled hydrogel, and this finding may provide useful insights for the development of effective delivery systems for specific applications.

Effects of Sodium Chloride on the Physical and Oxidative Stability of Filled Hydrogel Particles Fabricated with Phase Separation Behavior.

The objective of this study was to investigate the influence of sodium chloride (NaCl) concentration (0–500 mM) on the physical and oxidative stabilities of filled hydrogel that were stabilized using heat-denatured whey protein concentrate and high methoxy pectin. Our results showed that with an increase in NaCl concentration, the particle sizes, zeta-potentials, and interfacial layer thickness of filled hydrogels significantly increased and the lightness and whiteness gradually decreased (p < 0.05). Moreover, rheological characterization revealed that the apparent viscosity and viscoelastic behavior gradually decreased at higher NaCl concentration, which was mainly ascribed to the influence of NaCl on the electrostatic repulsion between droplets, thereby adversely impacting the physical stability of filled hydrogels. Furthermore, the result of cryo-scanning electron microscopy also verified the abovementioned results. Notably, higher NaCl concentration significantly promoted the oxidation of lipids and proteins (p < 0.05), thereby decreasing the oxidative stabilities of filled hydrogels. Our results indicated that filled hydrogels prepared under different ionic strength conditions can provide the theoretical basis for their future application in emulsion-based foods.

Transglutaminase crosslinking promotes physical and oxidative stability of filled hydrogel particles based on biopolymer phase separation

In the present study, the effect of transglutaminase (TGase) concentration on the physical and oxidative stabilities of filled hydrogel particles created by biopolymer phase separation was investigated. The results showed that filled hydrogels had relatively smaller particle sizes, higher absolute zeta-potentials, higher interfacial layer thicknesses and lightness values with the increasing of TGase concentration (P < 0.05), as evidenced by the apparent viscosity and viscoelasticity behavior. However, the relatively higher TGase concentration promoted the protein aggregation, which weakens the protection of the surface protein layer, having the negatively impacted the physical stability of filled hydrogels. Microstructural images which obtained via cryo-scanning electron microscopy also verified the above results. In particular, it is noted that filled hydrogels displayed the lowest degrees of lipid and protein oxidation during 10 days of storage (P < 0.05) at TGase concentration of 10 U/g. Prevention against oxidation was attributed mainly to TGase crosslinking of protein molecules on the surface of droplets, which likely provided a denser interface around lipid droplets. Our results indicated that TGase was a favourable agent to crosslink protein on the surface of lipid and improve the physical and oxidative stability of filled hydrogel particles.

Physical properties and stability of filled hydrogel particles based on biopolymer phase separation: Influence of the ratio of protein to polysaccharide

Filled hydrogel particles can be fabricated by incorporating an oil-in-water emulsion into portions of separated incompatible lower and upper phases together and remixing with later acidification to pH 5.0. The purpose of present study was to investigate the influence of different heat-denatured whey protein concentrates (HWPC)/high methoxy pectin (HMP) mass ratios (1:1, 2:1, 3:1, 4:1, and 5:1) of phase separated systems on the physical characteristics and stabilities of filled hydrogel particles. The results showed that the particle size of filled hydrogel particles significantly decreased with increasing HWPC/HMP mass ratios (P < 0.05), which was verified by reduced interfacial layer thickness. Moreover, decreased particle size also induced consistent reduction of the apparent viscosity and slightly increased the lightness. In particular, when the HWPC/HMP mass ratio was 3:1, the filled hydrogel particles exhibited the lowest amount of conjugated dienes and thiobarbituric acid-reactive substances after 10 days of storage (P < 0.05), which was mainly due to the highest amount of biopolymers distributed at the interfacial membrances (P < 0.05). Our results indicate that the phase separation system formed by HWPC/HMP mass ratio of 3:1 could be used to fabricate filled hydrogel particles with amplified stabilities at acidic pH for novel delivery systems.

Filled hydrogel particles as a delivery system for n − 3 long chain PUFA in low-fat frankfurters: Consequences for product characteristics with special reference to lipid oxidation

This article examines the suitability of filled hydrogel particles for use as a delivery system for n−3 long chain PUFAs in low-fat frankfurters. Their effects on product characteristics over chilled storage were compared with those of frankfurters containing all-pork fat (control) or a comparable amount of fish oil (n−3 LCPUFA) incorporated in liquid form or in an oil-in-water emulsion. In modified samples n−3 fatty acids ranged between 801.34 to 996.37mg/100g as opposed to 66mg/100g in all-pork fat product. As compared with the control, hardness and chewiness values were similar (P>0.05) in filled hydrogel frankfurter. The presence of fish oil favoured lipid oxidation to varying degrees depending on delivery system, in descending order: direct oil addition>oil-in-water emulsion>hydrogels. Sensory evaluation demonstrated the advantages, from a sensory point of view, of hydrogel filled particles as n−3 delivery systems in frankfurters.

Formation and characterization of filled hydrogel beads based on calcium alginate: Factors influencing nanoemulsion retention and release

Filled hydrogel particles fabricated from natural lipids and biopolymers can be utilized as tailor-made encapsulation and delivery systems. In the present study, the impact of nanoemulsion fabrication method (low energy versus high energy) on the retention and release of a lipophilic bioactive component (curcumin) and of lipid droplets from calcium alginate beads was investigated. Initially, curcumin was dissolved within an oil phase, and then the oil phase was encapsulated within the hydrogel beads using a two-step process. First, nanoemulsions composed of the same constituents (medium chain triglycerides, Tween 60, curcumin, and phosphate buffer) were prepared using either low energy (spontaneous emulsification) or high energy (microfluidization) homogenization. Second, the nanoemulsions were mixed with alginate solutions (0.25–1.5%), and then the resulting mixture was dripped into calcium solutions (10–500 mM) to form filled hydrogel beads. Unloaded beads became more spherical and rigid with increasing alginate and calcium concentrations. Turbidity and spectrophotometry measurements showed that the amount and extent of curcumin and lipid droplet release from the hydrogel beads decreased with increasing alginate and calcium concentration, which was attributed to a reduction in the pore size of the hydrogel matrix. In particular, a high amounts of curcumin released were observed in delivery systems containing high Tween 60 concentrations, which was attributed to rapid diffusion of curcumin-loaded surfactant micelles out of the beads. These results have important implications for the design of delivery systems to entrap and control the release of lipophilic bioactive components within filled hydrogel particles.

Oxidative stability of n-3 fatty acids encapsulated in filled hydrogel particles and of pork meat systems containing them

The effect of storage time (2°C, 19days) and heating (70°C, 30min) on physical characteristics and oxidative stability of fish oil encapsulated in filled hydrogel particles was determined and compared with a conventional oil-in-water (O/W) emulsion with the same oil content (8.5%). Subsequently they were used to enrich meat systems with n-3 LCPUFAs, and their lipid oxidation was evaluated and compared with two other meat systems: one containing all animal fat and another with fish oil added directly. Filled hydrogel particles were more effective in lowering the oxidation rate than O/W emulsion, even when thermal treatment was applied. Oxidative stability over the storage time was best in the n-3 LCPUFA-enriched meat system containing filled hydrogel particles, in which TBARS levels were up to 62% lower than other systems containing fish oil. Hydrogel particles offer a promising means of controlling lipid oxidation in n-3 LCPUFA-enriched meat products.

Fabrication, characterization and properties of filled hydrogel particles formed by the emulsion-template method

The purpose of this study was to fabricate filled hydrogel particles based on an emulsion-templating method that could be used as delivery systems. An oil-in-water-in-oil (O/W/O) emulsion was produced using a 2 step process: (i) an O/W emulsion was produced by high pressure homogenization of an oil phase with a water phase containing whey protein isolate (15% WPI, 100mM NaCl, pH 7); (ii) an O/W/O emulsion was produced by high shear mixing of the O/W emulsion with another oil phase. The O/W/O emulsion was then thermally processed (90°C, 30min), which caused the whey protein molecules to unfold and form a hydrogel in the water phase. The filled hydrogel particles (O/W) were isolated from the O/W/O emulsion by washing with n-hexane. These particles could be dispersed in aqueous solutions containing hydrophilic emulsifiers to inhibit aggregation. Confocal microscopy and spectroscopy measurements indicated that a high percentage of the internal oil phase remained encapsulated in the whey protein hydrogel particles (>94%). During storage for 7days at room temperature, there were no changes in the size or charge of the filled hydrogel particles. The results suggest that emulsion templating could be a suitable process of encapsulating and protecting labile lipids using hydrogel particles.

Food-grade filled hydrogels for oral delivery of lipophilic active ingredients: Temperature-triggered release microgels

Delivery systems are often needed to encapsulate lipophilic active agents, protect them during storage, and then release them within the mouth. In this study, gelatin and caseinate were used to fabricate temperature-sensitive filled hydrogel particles. Filled hydrogel microspheres were formed by electrostatic complexation of caseinate and gelatin in the presence of caseinate-coated lipid droplets. This was achieved by mixing aqueous 1% sodium caseinate and 1% gelatin solutions (volume ratio 1:2) at pH5.8 with an oil-in-water emulsion. The majority of lipid droplets were trapped within the hydrogel microspheres. Turbidity and viscosity measurements of the hydrogels indicated that hydrogel particles dissociated upon heating because of gelatin melting (around 35°C). Light scattering and confocal fluorescence microscopy indicated that lipid droplets were released from the gelatin-based hydrogel particles after oral processing, which was attributed to hydrogel melting under simulated mouth conditions. Our results suggest that hydrogel particles based on electrostatic complexation of sodium caseinate and gelatin could be useful as oral delivery systems for lipophilic active agents.

Retention and release of oil-in-water emulsions from filled hydrogel beads composed of calcium alginate: impact of emulsifier type and pH.

Delivery systems based on filled hydrogel particles (microgels) can be fabricated from natural food-grade lipids and biopolymers. The potential for controlling release characteristics by modulating the electrostatic interactions between emulsifier-coated lipid droplets and the biopolymer matrix within hydrogel particles was investigated. A multistage procedure was used to fabricate calcium alginate beads filled with lipid droplets stabilized by non-ionic, cationic, anionic, or zwitterionic emulsifiers. Oil-in-water emulsions stabilized by Tween 60, DTAB, SDS, or whey protein were prepared by microfluidization, mixed with various alginate solutions, and then microgels were formed by simple extrusion into calcium solutions. The microgels were placed into a series of buffer solutions with different pH values (2 to 11). Lipid droplets remained encapsulated under acidic and neutral conditions, but were released under highly basic conditions (pH 11) due to hydrogel swelling when the alginate concentration was sufficiently high. Lipid droplet release increased with decreasing alginate concentration, which could be attributed to an increase in the pore size of the hydrogel matrix. These results have important implications for the design of delivery systems to entrap and control the release of lipophilic bioactive components within filled hydrogel particles.

Structure–function relationships in food emulsions: Improving food quality and sensory perception

Increasing consumer demand for higher quality, cheaper, more convenient, and healthier emulsion-based products means that the food industry must have a good understanding of the relationship between the structural and functional properties of food emulsions. This review article provides an overview of the relationship between the composition and structural organization of oil-in-water emulsions and their physicochemical (optical, rheological, and stability) and sensory (appearance, texture, flavor, and mouthfeel) properties. It also discusses recent advances in the design of structured emulsions with novel functional properties, such as multiple emulsions, filled-hydrogel particles, multilayer emulsions, microclusters, and air-filled emulsions.

Oil-filled hydrogel particles for reduced-fat food applications: Fabrication, characterization, and properties

The food industry needs effective strategies to develop reduced calorie products with desirable sensory attributes. This study utilizes controlled phase separation of biopolymer mixtures to form oil-filled hydrogel particles suitable for use in food products. Filled hydrogel particles were fabricated from fat droplets (0 to 1%), sodium caseinate (1.5 to 3%) and high-methoxy pectin (1.5 to 3%) mixtures (pH 5) using two different approaches: multistep and simple methods. The multistep method involved inducing segregative phase separation of the mixed biopolymers at pH 7 (due to electrostatic repulsion), and then reducing to pH 5 to promote aggregative phase separation (due to electrostatic attraction). The simple method involved mixing all the components together at pH 7 and then adjusting to pH 5. The oil-filled hydrogel particles were spheroid in shape, with mean particle diameters (d43) around 10 μm. They consisted of fat droplets trapped within caseinate-rich hydrogel particles that were dispersed within a pectin-rich phase. The hydrogel particles increased the lightness and viscosity of aqueous solutions, and may therefore be suitable to replace fat droplets or starch granules in reduced calorie products. The food industry needs effective strategies to develop reduced calorie products with desirable sensory attributes. This study utilizes controlled phase separation of biopolymer mixtures to form oil-filled hydrogel particles suitable for use in food products. They consisted of fat droplets trapped within caseinate-rich hydrogel particles dispersed within a pectin-rich phase. The hydrogel particles increased the lightness and viscosity of aqueous solutions, and may be suitable to replace fat droplets or starch granules within reduced calorie products.

Hydrogel microspheres for encapsulation of lipophilic components: Optimization of fabrication & performance

Filled hydrogel microspheres consisting of small oil droplets trapped within biopolymer matrices are useful for encapsulating and delivering lipophilic bioactive agents. The aim of this study was to improve the current method of microsphere fabrication by increasing lipid loading capacity and microsphere yields, reducing the number of processing steps involved in fabrication, and creating microspheres that resist gravitational separation during storage. Filled hydrogel microspheres were fabricated from a phase separated mixture of pectin, caseinate, and emulsified oil to form an oil-in-water-in-water (O/W1/W2) emulsion. This system was then acidified and the resulting microspheres were cross-linked with transglutaminase. The order in which the biopolymer phases (W1 and W2) and oil droplets (O) were mixed together did not impact the lipid loading capacity. Decreasing the proportion of the continuous biopolymer phase (W2) used in the preparation procedure increased microsphere yields; however too low proportions (60–70%) caused excessive foaming and protein coagulation. Alternative methods of fabricating filled hydrogel particles using free oil (rather than emulsified oil) proved unsuccessful, resulting in the formation of large non-encapsulated oil droplets (d ∼ 10 μm). Hydrogel microspheres (d32 ∼ 3 μm) with high stability to gravitational separation could be produced by fabricating microspheres with an oil-to-biopolymer ratio of ∼2.6, since this ratio formed particles with a density that nearly matched the surrounding aqueous phase.

Factors Influencing the Formation and Stability of Filled Hydrogel Particles Fabricated by Protein/Polysaccharide Phase Separation and Enzymatic Cross-Linking

Filled hydrogel particles can be used to encapsulate, protect, and deliver lipophilic components. In this study, we investigated the influence of preparation conditions on the size of filled hydrogel particles created using biopolymer phase separation and enzymatic cross-linking. We then investigated the stability of these particles to external stresses: pH (pH 2–8); heat (40°–90 °C, 20 min); sodium chloride (0–500 mM); and calcium chloride (0–8 mM). Filled hydrogel particles were fabricated as follows: (i) high methoxy pectin, sodium caseinate, and caseinate-coated lipid droplets were mixed at pH 7 under conditions where phase separation due to thermodynamic incompatibility occurred; (ii) this mixture was acidified (pH 5) to induce adsorption of anionic pectin molecules around lipid-filled caseinate-rich particles; (iii) the caseinate within the particles was enzymatically cross-linked using transglutaminase. Three mixing conditions (0, 100, and 1,000 rpm) were tested during particle acidification. Particle size measurements indicated that larger particles were formed at 0 and 100 rpm than at 1,000 rpm. Under high pH conditions (pH 6–8), particles cross-linked with transglutaminase remained intact while control particles (not cross-linked) disintegrated. The addition of calcium to both control and cross-linked particles resulted in system gelation above 4 mM calcium chloride. Control and cross-linked particles remained stable to heating and to the addition of sodium chloride. Results from this study demonstrate the versatility and robustness of this delivery system for lipophilic bioactives.

Control of lipase digestibility of emulsified lipids by encapsulation within calcium alginate beads

Structured delivery systems, fabricated from natural lipids and polymers, are finding increasing use to improve the oral bioavailability of poorly water-soluble drugs and nutraceuticals, as well as to control the release of lipophilic bioactive molecules within the human gastrointestinal tract. This study focused on the development of filled hydrogel particles to control the digestion and release of encapsulated lipids. These filled hydrogel particles were fabricated by trapping sub-micron lipid droplets within calcium alginate beads. These particles remained intact when the pH was varied from 1 to 7, but exhibited some shrinkage at pH 1 and 2. The free fatty acids released from the filled hydrogel particles after addition of pancreatic lipase were monitored using a pH-stat in vitro digestion model. Encapsulation of lipid droplets within calcium alginate beads ( d = 2.4 mm) reduced the free fatty acids released from around 100% to less than 12% after 120 min. The rate and extent of lipid digestion increased with decreasing bead size (from 3.4 to 0.8 mm), decreasing degree of cross-linking ( i.e., lower calcium or alginate concentrations), and decreasing triglyceride molecular weight ( i.e., tributyrin > MCT ≈ corn oil). These results have important implications for the design of delivery systems to protect and release lipophilic bioactive components within the human body, as well as to modulate satiety/satiation by controlling the rate of lipid digestibility.

Fabrication and characterization of filled hydrogel particles based on sequential segregative and aggregative biopolymer phase separation

In this study, filled hydrogel particles were created based on the ability of proteins and ionic polysaccharides to phase separate through both aggregative (complexation) and segregative (incompatibility) mechanisms. At pH 7, a mixture of 3% (w/w) high-methoxy pectin and 3% (w/w) sodium caseinate phase separated through a segregative mechanism. Following centrifugation, the phase separated system consisted of an upper pectin-rich phase and a lower casein-rich phase. Casein-coated lipid droplets added to the phase separated pectin/caseinate system partitioning into the lower casein-rich phase. This was attributed to a reduction in the unfavorable osmotic stress in this phase associated with biopolymer depletion. When shear was applied this system formed an oil-in-water-in-water (O/W 1/W 2) emulsion consisting of oil droplets (O) contained within a casein-rich watery dispersed phase (W 1) suspended in a pectin-rich watery continuous phase (W 2). Acidification of the O/W 1/W 2 system from pH 7–5 promoted adsorption of pectin around the casein-rich W 1 droplets, resulting in the formation of filled hydrogel particles ( d = 3–4 μm) that remained stable to aggregation or dissociation when stored for 24 h at ambient temperature. These particles may be useful as encapsulation and delivery systems for lipophilic components in the food, cosmetics and pharmaceutical industries.

Emulsion Design to Improve the Delivery of Functional Lipophilic Components

The food industry has used emulsion science and technology for many years to create a diverse range of food products, such as milk, cream, soft drinks, nutritional beverages, dressings, mayonnaise, sauces, dips, deserts, ice cream, margarine, and butter. The majority of these food products are conventional oil-in-water (O/W) or water-in-oil (W/O) type emulsions. Recently, there has been increasing interest within the food industry in either improving or extending the functional performance of foods using novel structured emulsions. This article reviews recent developments in the creation of structured emulsions that could be used by the food and other industries, including nanoemulsions, multiple emulsions, multilayer emulsions, solid lipid particles, and filled hydrogel particles. These structured emulsions can be produced from food-grade [generally recognized as safe (GRAS)] ingredients (e.g., lipids, proteins, polysaccharides, surfactants, and minerals), using simple processing operations (e.g., mixing, homogenizing, and thermal processing). The structure, production, performance, and potential applications of each type of structured emulsion system are discussed.

Emulsion‐Based Delivery Systems for Lipophilic Bioactive Components

There is a pressing need for edible delivery systems to encapsulate, protect, and release bioactive lipids within the food, medical, and pharmaceutical industries. The fact that these delivery systems must be edible puts constraints on the type of ingredients and processing operations that can be used to create them. Emulsion technology is particularly suited for the design and fabrication of delivery systems for encapsulating bioactive lipids. This review provides a brief overview of the major bioactive lipids that need to be delivered within the food industry (for example, omega-3 fatty acids, carotenoids, and phytosterols), highlighting the main challenges to their current incorporation into foods. We then provide an overview of a number of emulsion-based technologies that could be used as edible delivery systems by the food and other industries, including conventional emulsions, multiple emulsions, multilayer emulsions, solid lipid particles, and filled hydrogel particles. Each of these delivery systems could be produced from food-grade (GRAS) ingredients (for example, lipids, proteins, polysaccharides, surfactants, and minerals) using simple processing operations (for example, mixing, homogenizing, and thermal processing). For each type of delivery system, we describe its structure, preparation, advantages, limitations, and potential applications. This knowledge can be used to facilitate the selection of the most appropriate emulsion-based delivery system for specific applications.