Fabrication and characterization of W/O/W emulsions with crystalline lipid phase

Electrostatic spraying encapsulation of probiotic-loaded W/O/W emulsion in sodium alginate microspheres to enhance probiotic survival stability

Water-oil-water (W/O/W) double emulsions have been widely studied and applied in probiotic encapsulation. However, challenges remain in enhancing emulsion stability, protecting encapsulated probiotics from adverse environmental conditions, and improving their viability. This study aimed to optimize the functional components of each phase of the W/O/W emulsion to address these issues. First, the prebiotic fructooligosaccharide, which promotes bacterial growth, was incorporated into the inner water phase. The oil phase (O) was composed of sunflower oil, polyglyceryl polyricinoleate, and different proportions of cocoa butter to investigate the critical role of cocoa butter in maintaining emulsion stability. The effect of varying ratios of whey protein isolate and gum arabic complexes in the outermost water phase on emulsion stability was also systematically investigated. Finally, combined with electrostatic spraying technology, sodium alginate was used as the encapsulating wall material for the probiotic-encapsulated emulsion, and the stability of the system during in vitro gastrointestinal digestion was evaluated. This study utilized electrostatic spray technology to create a protective "armor" around the emulsion encapsulating probiotics. The combination of emulsion encapsulation and electrostatic spray encapsulation significantly improved the survival stability of probiotics, providing a method for maintaining high viability in complex food media.

The effects of different types of polysaccharides on the structure and physical properties of W/O/W emulsions under varying pH conditions

BACKGROUND

Biopolymer based water-in-oil-in-water double (W1/O/W2) emulsion systems comprise a complex emulsion system that might be affected by several factors and the status at multiple phases. The present study investigated the physicochemical properties of W1/O/W2 double emulsions with inner W1 phase incorporated with various polysaccharides and the outer phase stabilized by whey protein isolate (WPI). Six different polysaccharides were selected as co-emulsifiers in the inner phase, and their effects on morphology, droplet size, zeta potential and rheology properties were evaluated. Furthermore, the impact of WPI/polysaccharide concentration and pH on the physicochemical properties and storage stability of the emulsions was compared.

RESULTS

Emulsions with an inner phase incorporated with xanthan gum and carrageenan exhibited better stability than others. Increasing the concentration of WPI enhanced the overall stability of the double emulsion, although it compromised the integrity of the internal W1/O interface. On the other hand, a 1.0% concentration of polysaccharide, specifically when carrageenan is used, slowed down droplet floating and coagulation. An acidic external aqueous phase (pH 4) led to larger and more uniform particle size distributions, as well as enhanced stability. The lower pH decreased the viscosity and delayed molecular exchange in the oil phase, thereby preserving the structure of the double emulsion.

CONCLUSION

These findings contribute to a better understanding of the factors influencing the stability and properties of W1/O/W2 double emulsions with addition of anionic polysaccharides in the inner water phase. © 2024 Society of Chemical Industry.

Nano-encapsulation of essential amino acids: ruminal methane, carbon monoxide, hydrogen sulfide and fermentation

This study aimed to evaluate the effect of nano-encapsulation of four essential amino acids (AA), threonine, methionine, tryptophan, and lysine on in vitro ruminal total gas, methane, carbon monoxide, and hydrogen sulfide production as well as the rumen fermentation profile in cattle. The highest (P < 0.001) rate and asymptotic gas production after 48 h of incubation was observed in the diets that had threonine, followed by lysine, methionine, and tryptophan. Asymptotic methane gas production decreased in the following order: threonine > lysine > tryptophan > methionine (P < 0.0001) and the rate of production per hour followed the same trend (P = 0.0259). CH4 parameters showed that in 4 h, 24 h, and 48 h of incubation the lowest methane production was obtained in the diet with methionine (P < 0.05) and the highest one in diet supplemented with threonine. Methane fractions showed that methionine-containing diets resulted in more (P < 0.05) metabolizable energy versus methane, followed by tryptophan-containing, and then lysine-containing diets. Methionine-fortified diets seem to be the most eco-friendly among those studied regarding methane output. However, based on methane, CO, and H2S output as well as the rumen fermentation profile nano-encapsulated lysine is recommended for use in ruminant nutrition.

Studies on the Properties and Stability Mechanism of Double Emulsion Gels Prepared by Heat-Induced Aggregates of Egg White Protein-Oligosaccharides Glycosylation Products

Multiple emulsions can dissolve some substances with different properties, such as hydrophilicity and lipophilicity, into different phases. They play an important role in protection, controlled release and targeted release of the encapsulated substances. However, it's poor stability has always been one of the main problems restricting its application in the food industry. For this reason, a heat-induced aggregate (HIA) of Maillard graft product of isomalto-oligosaccharides (IMO), as well as egg white protein (EWP), was used as hydrophilic emulsifier to improve the stability of W1/O/W2 emulsions. Moreover, gelatin was added into the internal aqueous phase (W1) to construct W1/O/W2 emulsion-gels system. The encapsulation efficiency of HIA-stabilized W1/O/W2 emulsions remained nearly unaltered, dropping by only 0.86%, significantly outperforming the conjugates and physical mixture of IMO and EWP in terms of encapsulation stability. The emulsion-gels system was constructed by adding 5% gelatin in the W1, and had the highest EE% and good salt and heat stability after 30 days of storage. This experiment provides guidance for improving the stability of W1/O/W2 emulsions system and its application in the package delivery of functional substances in the food field.

Co-delivery of hydrophobic β-carotene and hydrophilic riboflavin by novel water-in-oleic acid-in-water (W/OA/W) emulsions

Hydrophobic β-carotene and hydrophilic riboflavin offer a wide range of health benefits, but their limited stability and bioaccessibility pose challenges to their use in the food industry. This study developed a water-in-oleic acid-in-water (W/OA/W) emulsion. The effects of internal/external water phase emulsifiers were investigated on their microstructure, encapsulation efficiency, and stability. Only 0.05 wt% soybean-derived phosphatidylcholine was required as a lipophilic emulsifier to produce W/OA/W emulsions that can encapsulate both hydrophobic β-carotene and hydrophilic riboflavin. Compared to the commercial pea protein isolate (PPI), the PPI-xylooligosaccharide conjugate demonstrated superior performance as hydrophilic emulsifiers in stabilizing W/OA/W emulsions. The W/OA/W emulsion co-delivery system improved the thermal stability, light stability, and bioaccessibility of β-carotene, as well as the light stability of riboflavin. Overall, the W/OA/W emulsion holds great promise for application in natural food and for co-delivering hydrophobic and hydrophilic bioactive ingredients.

Effect of Diacylglycerol Crystallization on W/O/W Emulsion Stability, Controlled Release Properties and In Vitro Digestibility

Water-in-oil-in-water (W/O/W) emulsions with high-melting diacylglycerol (DAG) crystals incorporated in the oil droplets were fabricated and the compositions were optimized to achieve the best physical stability. The stability against osmotic pressure, encapsulation efficiency and in vitro release profiles of both water- and oil-soluble bioactives were investigated. The presence of interfacial crystallized DAG shells increased the emulsion stability by reducing the swelling and shrinkage of emulsions against osmotic pressure and heating treatment. DAG crystals located at the inner water/oil (W1/O) interface and the gelation of the inner phase by gelatin helped reduce the oil droplet size and slow down the salt release rate. The DAG and gelatin-contained double emulsion showed improved encapsulation efficiency of bioactives, especially for the epigallocatechin gallate (EGCG) during storage. The double emulsions with DAG had a lower digestion rate but higher bioaccessibility of EGCG and curcumin after in vitro digestion. DAG-stabilized double emulsions with a gelled inner phase thus can be applied as controlled delivery systems for bioactives by forming robust interfacial crystalline shells.

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.

Preparation and characterization of glucoamylase microcapsules prepared by W/O/W type complex coacervation freeze drying

Glucoamylase was often used in the brewing industry but was unstable to several environmental factors and reacted quickly to produce fermentable sugar, which limited its applications. Microencapsulation could effectively overcome the drawbacks. This study evaluated the feasibility of the preparation of glucoamylase microcapsules (GM) using W/O/W complex coacervation-freeze-drying method. The parameters of the microcapsules were optimized by the response surface optimization design: core-wall ratio at 1:1, wall-material concentration at 8%, and coagulation time for 20 min. Under current condition, the final microencapsulation efficiency reached 85.64 ± 1.60%. Glucoamylase could be slowly released for more than 96 h in the liquid state, and could react slowly for more than 336 h in the solid state. The optimized GM were incubated for 1 h, and the relative enzyme activity was better than that of free glucoamylase under high temperature conditions. The water capacity, solubility, morphology, differential scanning calorimetry, and Fourier transform infrared spectroscopy were conducted. Glucoamylase exhibited good sustained release characteristics. The microcapsules were more resistant to environmental stimuli and showed stronger robustness after optimization. PRACTICAL APPLICATION: Saccharification enzymes are often used in the winemaking industry, and direct addition will cause the fermentation process to heat up too quickly, resulting in the inactivation of microorganisms and saccharification enzymes, affecting the efficiency of saccharification enzymes. Therefore, microcapsules are used to encapsulate the saccharification enzyme, and its efficacy is slowly released for a long time during the fermentation process.

Preparation and characterization of W1 /O/W2 emulsions stabilized by glycated and heat-modified egg white proteins

BACKGROUND

Water-in-oil-in-water (W₁ /O/W₂ ) emulsions stabilized by protein-carbohydrate complexes were prepared from an inner water phase (W₁ ), an oil phase (O) and an outer water phase (W₂ ). The complexes consisted of heat-induced aggregates (HIAs) of isomalto-oligosaccharide/egg white protein Maillard conjugates. The effects of polyglycerol ester of polyricinoleic acid (PGPR) concentration, HIA concentration, W₁ -to-O volume ratio and W₁ /O-to-W₂ volume ratio on the properties of the W₁ /O/W₂ emulsions were systematically investigated.

RESULTS

At sufficiently high PGPR concentrations (>2%), the emulsions possess a high negative charge (≈-44 mV). The encapsulation efficiency of the emulsions, which was determined by incorporating a hydrophilic yellow dye in the inner water phase prior to homogenization, was relatively high (up to 93%) and did not change significantly during 14-day storage at 4 °C. All emulsions were fluids that exhibited shear thinning behavior.

CONCLUSION

Overall, this study shows that nature-derived emulsifiers can be used to create W₁ /O/W₂ emulsions suitable for application in the food industry. In addition, we provided a viable strategy to encapsulate water-soluble nutrients. © 2022 Society of Chemical Industry.

Encapsulation of amino acids in water-in-oil-in-water emulsions stabilized by gum arabic and xanthan gum

In this study, several kinds of amino acids were successfully encapsulated in a W₁/O/W₂ emulsion produced using a two-step emulsification process. Polyglycerol polyricinoleate (PGPR) was used as a hydrophobic emulsifier in the oil phase, while gum arabic (GA) and xanthan gum (XA) were used as an emulsifier and stabilizer in the outer water (W₂) phase, respectively. The stability and encapsulation efficiency of the W₁/O/W₂ emulsions depended on the ratio of W₁/O emulsion to W₂ phase, as well as the concentration of GA and XA within the outer W₂ phase. A W₁/O/W₂ emulsion prepared using 2 % (w/w) GA and 0.3 % (w/w) XA in the W₂ phase exhibited good stability and a high encapsulation efficiency (>80 %) for several amino acids. As the hydrophobicity of amino acids and storage temperature increased, the leakage from the W₁ to W₂ phases increased, which can be attributed to increasing solubility in the oil phase. The encapsulation efficiency of lysine encapsulated in GA-XA-stabilized W₁/O/W₂ double emulsion was over 84 % after 28 days storage at 4 °C. These results indicate that double emulsions may be useful for the encapsulation of amino acids, which may be useful to protect them from their environment and mask bitter flavors.

Progress in the Application of Food-Grade Emulsions

The detailed investigation of food-grade emulsions, which possess considerable structural and functional advantages, remains ongoing to enhance our understanding of these dispersion systems and to expand their application scope. This work reviews the applications of food-grade emulsions on the dispersed phase, interface structure, and macroscopic scales; further, it discusses the corresponding factors of influence, the selection and design of food dispersion systems, and the expansion of their application scope. Specifically, applications on the dispersed-phase scale mainly include delivery by soft matter carriers and auxiliary extraction/separation, while applications on the scale of the interface structure involve biphasic systems for enzymatic catalysis and systems that can influence substance digestion/absorption, washing, and disinfection. Future research on these scales should therefore focus on surface-active substances, real interface structure compositions, and the design of interface layers with antioxidant properties. By contrast, applications on the macroscopic scale mainly include the design of soft materials for structured food, in addition to various material applications and other emerging uses. In this case, future research should focus on the interactions between emulsion systems and food ingredients, the effects of food process engineering, safety, nutrition, and metabolism. Considering the ongoing research in this field, we believe that this review will be useful for researchers aiming to explore the applications of food-grade emulsions.

Impact of internal aqueous phase gelation on in vitro lipid digestion of epigallocatechin gallate-loaded W1 /O/W2 double emulsions incorporated in alginate hydrogel beads

Our objective was to investigate if the internal aqueous phase gelation of Water-in-oil-in-water double emulsions encapsulated in alginate beads would affect their structural stability and lipid hydrolysis during in vitro digestion. Therefore, bioactive molecules such as (-)-epigallocatechin gallate were encapsulated into different types of delivery systems: original double emulsions (as control) and incorporated double emulsions (filled in alginate hydrogel beads), both with non-gelled or gelled internal aqueous phase by locust bean gum and κ-carrageenan. After 2 h of gastric digestion, the gelled original emulsions showed smaller mean droplet diameters and less coalescence during the in vitro simulated gastrointestinal digestion compared to the non-gelled original emulsions. For the incorporated emulsions, oil droplets released from beads aggregated under intestinal conditions, and the rate of lipolysis was delayed. Interestingly, the internal aqueous phase gelation also impacted the rate and cumulative amount of free fatty acids (FFA) released. PRACTICAL APPLICATION: The combination of incorporating (-)-epigallocatechin gallate-loaded double emulsions into the alginate hydrogel matrix and gelling the internal aqueous phase was a benefit to regulating the rate and extent of lipid digestion for specific applications in foods, such as to control blood lipid levels and appetite.

Fabrication and Characterization of W/O/W Emulgels by Sipunculus nudus Salt-Soluble Proteins: Co-Encapsulation of Vitamin C and β-Carotene

W/O/W emulsions can be used to encapsulate both hydrophobic and hydrophilic bioactive as nutritional products. However, studies on protein stabilized gel-like W/O/W emulsions have rarely been reported, compared to the liquid state multiple emulsions. The purpose of this study was to investigate the effect of different oil–water ratios on the stability of W/O/W emulgels fabricated with salt-soluble proteins (SSPs) of Sipunculus nudus. The physical stability, structural characteristics, rheological properties, and encapsulation stability of vitamin C and β-carotene of double emulgels were investigated. The addition of W/O primary emulsion was determined to be 10% after the characterization of the morphology of double emulsion. The results of microstructure and rheological properties showed that the stability of W/O/W emulgels increased with the increasing concentration of SSPs. Additionally, the encapsulation efficiency of vitamin C and β-carotene were more than 87%, and 99%, respectively, and still could maintain around 50% retention of the antioxidant capacity after storage for 28 days at 4 °C. The aforementioned findings demonstrate that stable W/O/W emulgels are a viable option for active ingredients with an improvement in shelf stability and protection of functional activity.

Development and characterization of medium and high internal phase novel multiple Pickering emulsions stabilized by hordein nanoparticles

Medium and high internal phase W₁/O/W₂ multiple Pickering emulsions (MPEs) were fabricated by physically-modified hordein nanoparticles. A triphasic system was developed at dispersed phase volume fraction (Φ) of 0.5 with an overrun value of ∼40%. No overrun was detected in high internal phase MPEs (Φ 0.8). Optical and confocal laser scanning microscopy confirmed the formation of MPEs. Monomodal droplet size distribution with a mean diameter of 32.90 and 21.48 μm was observed for MPEs at Φ 0.5 and Φ 0.8, respectively. Static multiple light scattering confirmed that creaming was the main mechanism behind the instability of MPEs. Both MPEs revealed pseudo-plastic behavior and predominant storage modulus (G') over the applied frequency range. The encapsulation efficiency of vitamin B₁₂ in MPEs was 98.3% and remained relatively constant during 28 d. These results suggested the excellent potential of hordein nanoparticles as appropriate candidate for designing multi-structural colloidal systems using plant proteins.

Water-in-Oil-in-Water Double Emulsions as Protective Carriers for Sambucus nigra L. Coloring Systems

The use of natural colorants is needed to overcome consumer concerns regarding synthetic food colorants' safety. However, natural pigments have, in general, poor stability against environmental stresses such as temperature, ionic strength, moisture, light, and pH, among others. In this work, water-in-oil-in-water (W1/O/W2) emulsions were used as protective carriers to improve color stability of a hydrophilic Sambucus nigra L. extract against pH changes. The chemical system comprised water and corn oil as the aqueous and oil phases, respectively, and polyglycerol polyricinoleate (PGPR), Tween 80, and gum Arabic as stabilizers. The primary emulsion was prepared using a W1/O ratio of 40/60 (v/v). For the secondary emulsion, W1/O/W2, different (W1/O)/W2 ratios were tested with the 50/50 (v/v) formulation presenting the best stability, being selected as the coloring system to test in food matrices of different pH: natural yogurt (pH 4.65), rice drink (pH 6.01), cow milk (pH 6.47), and soy drink (pH 7.92). Compared to the direct use of the extract, the double emulsion solution gave rise to higher color stability with pH change and storage time, as corroborated by visual and statistical analysis.

Impact of fat crystallization on the resistance of W/O/W emulsions to osmotic stress: Potential for temperature-triggered release

Water-in-oil-in-water (W/O/W) emulsions can be designed to encapsulate, protect, and release both hydrophilic and hydrophobic functional compounds. In this study, we examined the impact of crystallizing the fat phase on the resistance of W/O/W emulsions to osmotic stress, with the aim of developing osmotic-responsive systems. Polyglycerol polyricinoleate (PGPR) was used as a hydrophobic surfactant to stabilize the inner water droplets, while Quillaja saponin and whey protein isolate (WPI) were used as hydrophilic surfactants to coat the oil droplets. The impact of fat crystallization was examined by using either a liquid (soybean oil, SO) or semi-solid (hydrogenated soybean oil, HSO) fat as the oil phase. An osmotic stress was generated by establishing a sucrose concentration gradient between the internal and external water phases. Alterations in the droplet size, morphology, and stability of the W/O/W emulsions was measured when the sucrose concentration gradient was changed. The W/O droplets in the SO-emulsions swelled/shrank when the external sucrose concentration was below/above the internal sucrose concentration, which is indicative of water diffusing into/out of the droplets. Conversely, there was no change in the size of the W/O droplets in the HSO-emulsions under the same conditions, which was attributed to the mechanical strength of the fat crystal network resisting swelling or shrinking. HSO-emulsions did exhibit swelling when they were heated above a critical temperature, due to melting of the fat crystals and disruption of the crystal network. Our results demonstrate that crystallization of the oil phase of W/O/W emulsions can prevent water transport due to osmotic stress, which may be useful for developing temperature-triggered delivery systems for application in foods, cosmetics, pharmaceuticals, or personal care products.