Oil-loaded Emulsions Research Articles

Effects of gelatin-transglutaminase crosslinking, vitamin addition, and storage temperature on the properties of curcumin/fish oil-loaded emulsions

Effects of gelatin-transglutaminase crosslinking, vitamin addition, and storage temperature on the properties of curcumin/fish oil-loaded emulsions

Optimization of spray drying process of buriti oil-loaded bilayer emulsions

Buriti oil is extracted from the fruits of a palm tree (Mauritia flexuosa L.) native to the Amazon rainforest, having one of the highest levels of β-carotene found in nature. The emulsification of buriti oil contributes to protecting the bioavailability of its bioactive compounds during processing. Drying oil-loaded emulsions is a way to produce microcapsules that have higher storage stability and expand the application possibilities of buriti oil. The objective of this work was to evaluate the impact of spray drying conditions on the microencapsulation of buriti oil, using response surface methodology. Bilayer emulsions were stabilized by whey protein isolate and high-methoxyl pectin and spray dried. The effects of inlet air temperature (154–196 °C) and feed flow rate (1.2–6.8 mL/min) on different properties of the microcapsules were evaluated. Higher air temperatures caused a positive effect on process yield but affected the color and encapsulation efficiency, while the increase in feed flow rate had a positive effect on the color of microcapsules. The higher drying rates negatively affected the microcapsules, resulting in larger and agglomerated particles, with the presence of holes in their surface. Surface models were obtained to predict color parameters of the microcapsules, which can be used as tools to quality control during processing. In general, the low drying rate resulted in microcapsules with suitable characteristics to ensure oil protection. The optimized spray drying process allows the production of buriti oil microcapsules with potential for application as natural pigments in the food industry.

Molecular modification of low-dissolution soy protein isolates by anionic xanthan gum, neutral guar gum, or neutral konjac glucomannan to improve the protein dissolution and stabilize fish oil emulsion

Herein, the effects of anionic xanthan gum (XG), neutral guar gum (GG), and neutral konjac glucomannan (KGM) on the dissolution, physicochemical properties, and emulsion stabilization ability of soy protein isolate (SPI)-polysaccharide conjugates were studied. The SPI-polysaccharide conjugates had better water dissolution than the insoluble SPI. Compared with SPI, SPI-polysaccharide conjugates had lower β-sheet (39.6 %–56.4 % vs. 47.3 %) and α-helix (13.0 %–13.2 % vs. 22.6 %) percentages, and higher β-turn (23.8 %–26.5 % vs. 11.0 %) percentages. The creaming stability of SPI-polysaccharide conjugate-stabilized fish oil-loaded emulsions mainly depended on polysaccharide type: SPI-XG (Creaming index: 0) > SPI-GG (Creaming index: 8.1 %–21.2 %) > SPI-KGM (18.1 %–40.4 %). In addition, it also depended on the SPI preparation concentrations, glycation times, and glycation pH. The modification by anionic XG induced no obvious emulsion creaming even after 14-day storage, which suggested that anionic polysaccharide might be the best polysaccharide to modify SPI for emulsion stabilization. This work provided useful information to modify insoluble proteins by polysaccharides for potential application.

Characterization and Antifungal Activity of Lemongrass Essential Oil-Loaded Nanoemulsion Stabilized by Carboxylated Cellulose Nanofibrils and Surfactant.

Nanocellulose is an emerging green, biodegradable and biocompatible nanomaterial with negligible toxicities. In this study, a carboxylated nanocellulose (i.e., 2,2,6,6-tetramethylpiperidin-1-oxyl (TEMPO)-oxidized cellulose nanofibril (TEMPO-CNF)) was prepared from corn stover and characterized by X-ray diffraction (XRD), Fourier Transform Infrared Spectroscopy (FTIR) and differential scanning calorimetry (DSC)/thermogravimetric analysis (TGA). Corn stover-derived TEMPO-CNF was explored as an emulsion co-stabilizer together with Tween 80 for lemongrass essential oil-loaded emulsions. Droplet size, phase behavior and thermodynamic stability of oil-in-water emulsions stabilized by Tween 80 and TEMPO-CNF were investigated. The optimal nanoemulsion stabilized by this binary stabilizer could achieve a mean particle size of 19 nm, and it did not form any phase separation against centrifugal forces, freeze-thaw cycles and at least 30 days of room temperature storage. The nanoencapsulated essential oil had better inhibition activity against the mycelial growth of Aspergillus flavus than pure essential oil. Results from this study demonstrate the potential of using agricultural byproduct-derived nanomaterial as nanoemulsion stabilizers for essential oils with good emulsion thermodynamic stability as well as enhanced antifungal activities.

Effects of octenyl succinic anhydride chemical modification and surfactant physical modification of bovine bone gelatin on the stabilization of fish oil-loaded emulsions.

In this work, octenyl succinic anhydride (OSA) chemical modification with surfactant physical modification was combined to modify bovine bone gelatin (BBG) for emulsion stabilization at pH 6.0 (to simulate acidic food environment). OSA modification decreased the β-sheet percentage and increased β-turn percentage of BBG. Further, the combination of OSA modification with surfactant physical modification had obvious and different effects on the emulsifying properties of BBG. The creaming stability of gelatin/surfactant-stabilized emulsions was dependent on gelatin structure, surfactant type, and preparation pH. The emulsions stabilized by OBBG/Span 80 and OBBG/soybean lecithin (only blurry creaming at day 28) had significantly better creaming stability than other emulsions. These results demonstrated that the combination of OSA modification with surfactant modification could be applied to improve the emulsifying properties of BBG.

Fish gelatin-polysaccharide Maillard products for fish oil-loaded emulsion stabilization: Effects of polysaccharide type, reaction time, and reaction pH

Herein, the effects of polysaccharide types (xanthan gum, XG; guar gum, GG; and konjac glucomannan, KGM), reaction time (0–24 h), and reaction pH (5–9) on the fish gelatin (FG)-polysaccharide Maillard products for the stabilization of fish oil-loaded emulsions were studied. FG-polysaccharide complexes also showed better emulsifying properties than pure fish gelatin and pure polysaccharides. Further, the formation, physicochemical properties, and emulsifying properties of FG-polysaccharide Maillard products were dependent on polysaccharide type, reaction time, and reaction pH. Maillard conjugates had the best emulsifying properties (FG-GG: 0% of creaming index (CI); FG-KGM: 21.1% ± 0.7% of CI) among the FG-GG and FG-KGM Millard products, whereas the intermediate products (intermediates and fish gelatin) had the best emulsifying properties (0% of CI) among the FG-XG Maillard products. This work provided useful information to apply FP-polysaccharide Maillard products for the stabilization of fish oil-loaded emulsions in the field of food science.

Effect of β-cyclodextrin deodorization on the volatile chemicals and functional properties of three types of gelatins.

The exploration of deodorization is important for the application of gelatin in food industry. In this work, the effect of β-cyclodextrin (β-CD) deodorization on the volatile chemicals and functional properties of three types of gelatins (commercial porcine skin gelatin, cold water fish skin gelatin, and Chinese longsnout catfish skin gelatin) were studied. The results suggested the odors of commercial gelatins were significantly less than home-extracted gelatins. The β-CD deodorization efficiency was dependent on both β-CD concentration and volatile chemical. (E)-2-Octenal (C8H14O), 1-octen-3-ol (C8H16O), 2-pentyl-furan (C9H14O), and hentriacontane (C17H36) could be deodorized at low β-CD concentration (even at 2 mg/mL). The best β-CD deodorization concentration for 66.7 mg/mL of Chinese longsnout catfish skin gelatin was 30 mg/mL. β-CD addition could not change the gel forming ability and emulsion activity of gelatins, whereas it had different and concentration-dependent effects on the emulsion stability of gelatins. β-CD addition had no obvious effects on the droplet sizes, droplet coalescence and liquid-gel transition behaviors, but had different effects on the creaming of the emulsions stabilized by three types of gelatins. The encapsulation of β-carotene did not significantly change the droplet trimodal size distribution and liquid-gel transition of fish oil-loaded emulsions. However, β-carotene might delay the droplet coalescence. The creaming stability of β-carotene/fish oil-loaded gelatin/β-CD-stabilized emulsions was dependent on the gelatins, β-CD, and β-carotene. Finally, the β-carotene retention in the emulsions was dependent not on β-CD addition but on the nature of the gelatins. These results provided useful information to understand the molecular deodorization behaviors and explore the deodorization of emulsifiers for food emulsions.

Effects of tannic acid interfacial absorption on the physicochemical stability of algal oil-loaded emulsions and inhibition of fishy off-flavor

In the present study, the inhibition of fishy off-flavor and destabilization in algae oil-loaded emulsions by tannic acid (TA) adsorption on octenyl succinic anhydride (OSA) starch interfaces were investigated. The changes of typical fishy off-flavor components in the emulsion, physiochemical stability, and interaction between TA and OSA starch were analyzed. The TA fortification significantly prevented the production of fishy smell-related volatile components such as heptanal and (E, E)-3, 5-octadiene-2-one. The proportion of TA on the interface was more than 90 %, forming an interfacial film with the antioxidant function. The emulsions stabilized by OSA starch-TA complexes had better oxidative and physical stability. The isothermal titration calorimetry suggested that the interaction between OSA starch and TA included hydrogen bonding and van der Waals forces (ΔG = -13.272 kJ·mol−1·K−1, ΔH = -1.302 × 103 kJ·mol−1, ΔS = -4.326 kJ·mol−1·K−1). Altogether, these results provided application guidance for developing starch-based oil-in-water emulsion systems with antioxidant properties.

Effect of extraction methods on the properties of tilapia scale gelatins

Three types of tilapia scale gelatins (hot water-pretreated gelatin, HWG; acetic acid-pretreated gelatin, AAG; and pepsin enzyme-pretreated gelatin, PEG) were extracted and their gel strength, foaming properties, and emulsifying properties were analyzed. They had different gel strength values: AAG (370 ± 10 g Bloom) > HWG (320 ± 10 g Bloom) > PEG (280 ± 10 g Bloom). The creaming index values of tilapia scale gelatin-stabilized fish oil-loaded emulsions were dependent on gelatin type (HWG ≈ AAG > PEG) at low gelatin concentration (2 mg/mL), whereas they were similar and low (8–10 %) at high gelatin concentration (10 mg/mL). Extraction methods had no consistently significant effects on the gelatin foaming properties. In summary, tilapia scale gelatins had better gel strength and foaming properties and similar or even better emulsifying properties than mammalian gelatins. Therefore, tilapia scales could be a potential source of gelatins to replace mammalian gelatins.

Effects of antioxidant types on the stabilization and in vitro digestion behaviors of silver carp scale gelatin-stabilized fish oil-loaded emulsions

Lipid oxidation is a major challenge in the development and storage of lipid-containing food products. In this work, we extracted aquatic gelatin from silver carp scales and studied the effects of antioxidant types (water-soluble and lipid-soluble types) on the stabilization, lipid oxidation, and in vitro digestion behaviors of silver carp scale gelatin-stabilized fish oil-loaded emulsions. Vitamin C (VC), a water-soluble antioxidant, and vitamin E (VE), a lipid-soluble antioxidant, had no obvious effects on the appearance, droplet size distribution, and droplet stability of the emulsion. VC slowed the liquid-gel transition of the emulsions at room temperature. The emulsion creaming stability decreased with the increase of VC concentration, whereas it increased with the increase of VE concentration. Lipid oxidation hierarchy of emulsion groups at room temperature were VC<VE<control<pure oil. Free fatty acids were mainly released from the silver carp scale gelatin-stabilized emulsions in the simulated intestinal fluid. Moreover, compared with the control group, VC increased the free fatty acid release percentages, whereas VE decreased them. This work provided useful information for developing antioxidants in the field of food science and in value-added utilization research of aquatic by-products.

Effect of transglutaminase crosslinking on the structural, physicochemical, functional, and emulsion stabilization properties of three types of gelatins

Molecular modification has attracted many attentions in the field of gelatin science. In this work, a transglutaminase (TG) modification method was developed and applied to modify bovine bone gelatin, porcine skin gelatin, and cold-water fish skin gelatin, and then the effect of TG crosslinking on the structural, physicochemical, functional, and emulsion stabilization properties of three types of gelatins were explored and compared. The results demonstrated that TG modification increased the nanoparticle formation behaviors and change the physicochemical and functional properties of three types of gelatins. Further, TG-modified aquatic gelatin showed comparable foaming properties (147% ± 6% for foaming capability and 55% ± 4% for foam stability) and higher emulsifying properties (18 ± 1 m2/g for emulsion activity index and 142 ± 11 min for emulsion stability index) to unmodified mammalian gelatins. In addition, TG-modified gelatins decreased the droplet sizes and increased creaming stability of fish oil-loaded emulsions compared with unmodified gelatins. All these results suggested TG modification was an efficient molecular modification method for gelatins. Moreover, TG-modified aquatic gelatin could be potential mammalian gelatin replacer. This work could provide useful information to understand the relationship among animal sources, tissue sources, extraction methods, amino acid compositions, molecular modification, molecular structure, physicochemical properties, functional properties, and emulsification stability of gelatins.

Effect of carbon numbers and structures of monosaccharides on the glycosylation and emulsion stabilization ability of gelatin

Herein, the effect of saccharide glycosylation by nine monosaccharides on bovine bone gelatin for the stabilization of fish oil-loaded emulsions was explored. The gelatin modification was analyzed and then the emulsifying properties of monosaccharide-modified gelatins were analyzed at pH 9.0 and 3.0. The results demonstrated that glycosylated gelatin structure, droplet stability, creaming stability, and liquid-gel transition time were dependent on monosaccharide carbon numbers, monosaccharide structures, and solution pH. Glycosylation modification of gelatins did not obviously change the emulsion droplet stability at pH 9.0, whereas it increased the emulsion droplet stability at pH 3.0. Glycosylation modification of gelatins did not obviously change the emulsion creaming index values (5.1%–8.4% at pH 9.0 and 25.8%–33.1% at pH 3.0). Three-carbon and four-carbon monosaccharides glycosylation significantly increased emulsion liquid-gel transition times. This work provided useful information to understand the effects of carbon numbers and structures of monosaccharides on the protein modification.

Effects of phospholipid type and concentration on the emulsion stability and in vitro digestion behaviors of fish oil-loaded emulsions

Effects of phospholipid type and concentration on the emulsion stability and in vitro digestion behaviors of fish oil-loaded emulsions

Anhydride structures affect the acylation modification and emulsion stabilization ability of mammalian and fish gelatins

In this work, ring-like anhydrides (C4, C5, and C6) with different sizes and succinic anhydrides (C4, C10, C12, C14, and C16) with different side chain lengths were used to modify bovine bone gelatin (BBG) and cold-water fish skin gelatin (CFG), and the effect of acylated gelatins on fish oil-loaded emulsions stability was explored. The results showed that the degree of N-acylation decreased with increased ring sizes or side chain lengths, and the surface hydrophobicity of acylated gelatins increased with increased anhydride carbon numbers. Acylated CFGs had higher droplet stability and lower liquid-gel transition time than acylated BBGs. Only BBG-C12 had a slight increase on the creaming stability among these acylated gelatins. These results demonstrated that the gelatins could be modified by all the anhydrides and their emulsion stabilization ability was dependent on the gelatin type and anhydride structure. The results could be beneficial for protein-based emulsifier development and application.

Silver carp scale gelatins for the stabilization of fish oil-loaded emulsions

Herein, three types of silver carp scale gelatins were extracted, and their molecular weight distribution, structural properties, functional properties and emulsifying properties were investigated and discussed. Acetic acid-extracted gelatin (AAG), hot water-extracted gelatin (HWG), and pepsin enzyme-extracted gelatin (PEG) showed similar and four clear bands in sodium dodecyl sulfate-polyacrylamide gel electrophoresis pattern, whereas they showed different β chain amounts and β-sheet percentages. The water-holding capacity values (g/g of gelatin) were: AAG (16.8 ± 1.1) > HWG (14.0 ± 0.7) ≈ PEG (13.5 ± 1.6). The fat-binding capacity values (g/g of gelatin) were: AAG (11.8 ± 0.3) > HWG (9.5 ± 1.3) > PEG (5.3 ± 0.4). Emulsion droplet sizes and creaming index values decreased with the increase of gelatin concentrations for all the fish oil-loaded emulsions stabilized by three types of gelatins. Compared with PEG, AAG and HWG show similar and higher emulsion stability at high gelatin concentration (10 mg/mL). The stabilization mechanism of fish oil-loaded silver carp scale gelatin-stabilized emulsions involved an “extraction method-protein molecular weight distribution-protein molecular structure-molecular interaction-emulsibility-droplet structure-emulsion stability” route. This work would be beneficial for the research on the relationship of structure and function of gelatin and to the comprehensive utilization of aquatic products.

Formulation and Evaluation of Spray-Dried Reconstituted Flaxseed Oil-in-Water Emulsions Based on Flaxseed Oil Cake Extract as Emulsifying and Stabilizing Agent.

Spray drying of emulsions is a promising way of increasing their durability, offering the possibility of reconstitution, with the addition of water. The present study aimed to examine the properties of flaxseed oil cake extract (FOCE) as an emulsifying and stabilizing agent for spray-dried reconstituted oil-in-water emulsions. Maltodextrin: starch: flaxseed oil emulsions with FOCE or distilled water as liquid phases, and 10% and 20% of oil were spray-dried at 180 °C. The solubility, flowability, cohesiveness, bulk, and tapped densities of the spray-dried powders were analyzed. Additionally, the characteristics of initial and reconstituted emulsions, such as stability, creaming index, color, particle size, and rheological properties were evaluated. Results showed that FOCE could be an adequate emulsifier for spray-dried emulsions with a high oil content providing high stability after reconstitution, when compared to emulsions based only on maltodextrin–starch wall material with water as the liquid phase. This study showed an encouraging way for producing natural and plant-based spray-dried oil-loaded emulsions for food applications.

Processing and Formulation Optimization of Mandarin Essential Oil-Loaded Emulsions Developed by Microfluidization

Emulsions can be used as delivery systems for bioactive ingredients for their incorporation in food products. Essential oils are natural compounds found in plants that present antioxidant and antimicrobial activity. Therefore, the main goal of this work was to develop emulsions, containing mandarin essential oil stabilized by two food-grade surfactants and guar gum, and to evaluate their physical stability. The initial droplet size of emulsions developed by microfluidization was optimized, obtaining diameters below one micron regardless of the processing conditions. However, the emulsion processed at 25,000 psi and one pass exhibited the lowest mean droplet sizes and polidispersity, and therefore, a higher stability. Different ratios of Tween 80 and Span 80 were assessed as stabilizers. Results obtained indicated that the ratio of surfactants had a significant effect on the mean droplet sizes, physical stability, and rheological properties. Thus, we found that the optimum ratio of surfactants was 75/25 (Tween80/Span80) on account of the lowest droplet mean diameters, lack of coalescence, and a low creaming rate. The rheological characterization of the stable emulsions showed a shear thinning flow behavior, and G″ (loss modulus) values higher than G′ (storage modulus) values, in all the frequency range. The rheological behavior may be governed by the guar gum, which was confirmed by field emission scanning electron microscopy (FESEM). This research can be considered as the starting point for future applications of mandarin essential oil in emulsions, which can be incorporated in products as food preservatives.

Octenyl succinic anhydride modification of bovine bone and fish skin gelatins and their application for fish oil-loaded emulsions

Molecular modification of emulsifiers has attracted many attentions in the field of emulsions. In this work, an octenyl succinic anhydride (OSA) modification method is developed to modify bovine bone gelatins and fish skin gelatins, and then the effect of OSA modification on the gelatins and their application for fish oil-loaded emulsions are explored and compared. The results demonstrate that OSA can be successfully applied to modify gelatins and change their isoelectric points. Moreover, the degree of succinylation (DS) logarithmically increases with OSA-gelatin mass ratios in the chemical reaction process. Further, the OSA modification has no obvious effects on the initial emulsion droplet sizes of fish oil-loaded emulsions. Finally, the emulsion storage experiments suggest that the DS increase of OSA-modified bovine bone gelatins increases the droplet stability, phase transition time, and creaming index of fish oil-loaded emulsions, whereas the DS increase of OSA-modified fish skin gelatins only increases the droplet stability and has no obvious effects on the phase transition and creaming index of fish oil-loaded emulsions. This work will provide useful information to understand the relationship among molecular modification, molecular structure, and function of protein. It also will provide a potential route to optimize the preparation and application of fish oil-loaded emulsions in the field of food and drug industries.

Gelatin-stabilized traditional emulsions: Emulsion forms, droplets, and storage stability

Fish oils are important substances in the field of food and drug delivery. Due to their unstable double bonds, fishy taste, and poor water solubility, it is pivotal to investigate novel dosage forms for fish oils, such as encapsulated droplets. In this work, we primarily prepared gelatin-stabilized fish oil-loaded traditional emulsions and investigated their emulsion forms, droplets, and storage stability under different preparation and storage conditions. Our results showed that higher gelatin solution pH, higher storage temperature in the range of 4–37 °C, and increased storage time induced the emulsion form switch from a liquid form to a redispersible gel form of the fish oil emulsion. The droplets had core-shell microstructures and a trimodal size distribution, which decreases linearly with increasing gelatin solution pH and homogenizing time, but decreases exponentially with increasing homogenizing speed. In addition, storage temperature showed a notably different effect on traditional emulsion storage. This work provides a fundamental knowledge for the formation, microstructure, and properties of gelatin-based traditional emulsions. It also provides a promising new application for fish oil-loaded emulsions in food beverages, soft candy, and other food products.

Droplet and creaming stability of fish oil-loaded gelatin/surfactant-stabilized emulsions depends on both the adsorption ways of emulsifiers and the adjusted pH

The droplet and creaming stability of food emulsions stabilized by mixed emulsifiers is a research hotspot in the field of emulsions. In this work, we mainly explore the effect of pH change on the droplet and creaming stability of fish oil-loaded emulsions synergetically (Span 80 and SL) or competitively (Tween 80 and SDS) stabilized by gelatin/surfactant. The results demonstrate that initial droplet stability and droplet storage stability, and creaming stability of the pH-adjusted emulsions are dependent on both the adsorption ways of emulsifiers and the adjusted pH: (1) Competitively stabilized emulsions have more stable droplets than synergetically stabilized emulsions; (2) SDS-dominant competitively stabilized emulsions have more stable droplets than gelatin-dominant emulsions; (3) Basic pH-adjusted emulsions have more stable droplets than acidic pH-adjusted emulsions; (4) The synergetically stabilized emulsions at acidic pH have significantly higher creaming indexes than that at basic pH; and (5) The competitively stabilized emulsions have high or similar creaming indexes to that at acidic pH. Further, the mechanisms are proposed according to Stokes’ Law. This work will provide useful information to understand the interfacial properties of mixed emulsifiers in the food emulsions and promising application perspective for the development of food beverages including acidic and alkali beverages.