Formation Of Smaller Oil Droplets Research Articles

Effect of protein oxidation on the structure and emulsifying properties of fish gelatin

This study aimed to investigate the effect of oxidation on fish gelatin and its emulsifying properties. Fish gelatin was oxidized with varying concentrations of H2O2 (0–30 mM). Increased concentrations of the oxidant led to a decrease in amino acids in the gelatin, including glycine, lysine, and arginine. Additionally, the relative content of ordered secondary structure and triple helix fractions decreased. Zeta potential decreased, while particle size, surface hydrophobicity, and water contact angle increased. Regarding emulsifying behavior, oxidation promoted the adsorption of gelatin to the oil–water interface and reduced interfacial tension. With increased degrees of oxidation, the zeta potential and size of the emulsion droplets decreased. The oxidized gelatin exhibited better emulsifying activity but worse emulsifying stability. Based on these results, a mechanism for how oxidation affects the emulsifying properties of gelatin was proposed: the increase in gelatin’s hydrophobicity and the decrease in triple helix structure induced by oxidation reduced the interfacial tension at the oil–water interface. This promoted protein adsorption at the oil–water interface, allowing the formation of smaller oil droplets and enhancing gelatin’s emulsifying activity. However, the decrease in electrostatic repulsion between emulsion droplets and the decrease in solution viscosity increased the flocculation and aggregation of oil droplets, ultimately weakening the emulsifying stability of gelatin.

Improvement of Oxidative Stability of Fish Oil-in-Water Emulsions through Partitioning of Sesamol at the Interface

The susceptibility of polyunsaturated fatty acids to oxidation severely limits their application in functional emulsified foods. In this study, the effect of sesamol concentration on the physicochemical properties of WPI-stabilized fish oil emulsions was investigated, focusing on the relationship between sesamol-WPI interactions and interfacial behavior. The results relating to particle size, zeta-potential, microstructure, and appearance showed that 0.09% (w/v) sesamol promoted the formation of small oil droplets and inhibited oil droplet aggregation. Furthermore, the addition of sesamol significantly reduced the formation of hydrogen peroxide, generation of secondary reaction products during storage, and degree of protein oxidation in the emulsions. Molecular docking and isothermal titration calorimetry showed that the interaction between sesamol and β-LG was mainly mediated by hydrogen bonds and hydrophobic interactions. Our results show that sesamol binds to interfacial proteins mainly through hydrogen bonding, and increasing the interfacial sesamol content reduces the interfacial tension and improves the physical and oxidative stability of the emulsion.

Study of dextrin addition on the formation and physicochemical properties of whey protein-stabilized emulsion: Effect of dextrin molecular dimension

Oil-in-water (O/W) emulsion was prepared using whey protein as a natural emulsifier, and dextrin was incorporated with the emulsion formation. Dextrins with varying molecular dimensions (from 21.6 to 101.3 nm) were obtained by controlled enzymatic hydrolysis with α-amylase. The effects of molecular dimension of dextrin on the formation, stability, and physicochemical properties of the emulsions were then analyzed, by measuring their visual appearance, microstructure, particle size, zeta-potential, and rheological properties. Moreover, the environmental stress was assessed by temperature, pH, and ionic strength. The results indicated the presence of dextrin did not adversely affect the formation of small oil droplets during homogenization and the short-term stability of O/W emulsion. While in long-term storage, the emulsion with large dextrin and starch molecule was unstable to aggregate, and small dextrin could cooperate well in stabilizing the oil droplets in the emulsion system. A shear-thinning behavior was observed in all emulsions, and an increase in the emulsion viscosity (from 2.1 to 7.7 mPa.s) was examined with the addition of dextrin. Environmental stress of emulsion with low dimension dextrin was determined, indicating it was relatively thermal-stable. And some aggregations were found in emulsions near pH 4 and 5, as well as with NaCl addition. These results suggest that whey protein with low dimension dextrin addition may be a useful emulsifier for utilization within the food industry.

PH influences the interfacial properties of blue whiting (M. poutassou) and whey protein hydrolysates determining the physical stability of fish oil-in-water emulsions

This work investigates the influence of the interfacial properties of whey protein (WPH) and blue whiting protein (BPH) hydrolysates on the physical stability of fish oil-in-water emulsions stabilized with these hydrolysates at pH 2 or 8. Measurements of interfacial tension and dilatational rheology confirmed that pH is a key factor affecting these interfacial properties of WPH and BPH. WPH, when tested at 1 and 10 mg/mL, showed a higher interfacial activity at pH 8 when compared to pH 2 or to BPH at pH 8 or 2, despite having a lower protein content. Moreover, when tested at 0.1 and 1 mg/mL, the dilatational modulus of WPH was significantly higher at pH 8 than at pH 2. These findings correlate with the formation of smaller oil droplets and a more resistant interfacial peptide layer for WPH at pH 8, hence explaining the improved physical stability of the 5% fish oil-in-water emulsion stabilized with WPH at pH 8. BPH did not show significant differences in interfacial activity with pH but exhibited significantly higher dilatational elasticity and viscosity at pH 2 compared to pH 8 (when measured at 0.1 mg/mL and 0.01 or 0.1 Hz). This correlates with the formation of stable 5% fish oil-in-water emulsions with BPH at pH 2 but not at pH 8.

Enhancing lycopene stability and bioaccessibility in homogenized tomato pulp using emulsion design principles

The objective of this study was to examine the impact of oil, emulsifier, and texture modifier addition on the bioaccessibility of lycopene in homogenized tomato pulp. Different types (olive or corn oil) and levels (0 to 8 wt%) of digestible lipids, a protein-based emulsifier (whey protein isolate, WPI) and/or a polysaccharide-based texture modifier (sodium alginate, SA) were added to the tomato pulp. The addition of these substances increased the amount of lycopene liberated from the tomato tissues. WPI addition led to the formation of smaller oil droplets during homogenization that scattered light more strongly, thereby leading to a tomato pulp that appeared more turbid. SA addition increased the viscosity of the tomato pulp, thereby increasing its uniformity. The best storage stability of lycopene in the tomato pulp was achieved by adding 8% corn oil and 1% WPI. However, the best in vitro bioaccessibility of lycopene (61.5%) was achieved using 6% olive oil and 1% SA. Overall, our results show that lycopene bioaccessibility in tomato products can be increased by careful manipulation of emulsion properties.Industrial relevance: Lycopene is a strongly hydrophobic carotenoid found in tomatoes that contributes to their desirable appearance and potential health benefits. However, it has poor chemical stability and low oral bioavailability, which limits its beneficial effects. We show that the stability and bioaccessibility of lycopene can be improved by high-pressure homogenization of tomato pulp in the presence of specific food additives. This approach may be suitable for the large-scale production of tomato products with enhanced health benefits.

Corn Oil-Water Separation: Interactions of Proteins and Surfactants at Corn Oil/Water Interfaces.

Purification and collection of industrial products from oil-water mixtures are commonly implemented processes. However, the efficiencies of such processes can be severely influenced by the presence of emulsifiers that induce the formation of small oil droplets dispersed in the mixtures. Understanding of this emulsifying effect and its counteractions which occur at the oil/water interface is therefore necessary for the improvement of designs of these processes. In this paper, we investigated the interfacial mechanisms of protein-induced emulsification and the opposing surfactant-induced demulsification related to corn oil refinement. At corn oil/water interfaces, the pH-dependent emulsifying function of zein protein, which is the major storage protein of corn, was elucidated by the surface/interface-sensitive sum frequency generation (SFG) vibrational spectroscopy technique. The effective stabilization of corn oil droplets by zein protein was illustrated and correlated to its ordered amide I group at the oil/water interface. Substantial decrease of this ordering with the addition of three industrial surfactants to corn oil-zein solution mixtures was also observed using SFG, which explains the surfactant-induced destabilization and coalescence of small oil droplets. Surfactant-protein interaction was then demonstrated to be the driving force for the disordering of interfacial proteins, either by disrupting protein layers or partially excluding protein molecules from the interface. The ordered zein proteins at the interface were therefore revealed to be the critical factor for the formation of corn oil-water emulsion.

Phase behavior and stability of nano-emulsions prepared by D phase emulsification method

D phase emulsification method was applied to prepare nano-emulsions in the Span 80-Tween 80/glycerin/water/mineral oil system. The phase behavior of this system during the entire emulsification process and the stability of the prepared emulsions were investigated by means of a pseudo-ternary phase experimental design. A possible emulsification mechanism was preliminarily proposed on the basis of our experimental results. It was found that the special self-assembled structure of the D phase and its capability for oil phase were the crucial factors in the D phase emulsification. Firstly, the surfactant alignment of the D phase was beneficial to the formation of small oil droplets in the O/D phase. Then, a quick movement of the surfactants toward the oil-water interface was critical for preparing nano-emulsions. Furthermore, the stability of the nano-emulsions during storage (30 days) was predominantly related to the addition amount of surfactants. The higher the content of surfactant in the system, the more stable the nano-particle interface film was formed. The stable interface film avoids the aggregation of the particles due to the thermal motion of the molecules, and the nano-particles could remain stable during storage.

Dietary glycerol monolaurate supplementation for the modification of functional properties of egg white protein.

Understanding the interactions between feed additives and the functional properties of egg white protein (EWP) may offer novel insights into the effects of feed additives on laying hens and may provide an alternative for modification of the functional properties of EWP by using laying hens as bioreactors. Glycerol monolaurate (GML) is widely used in the food industry as an effective antibacterial emulsifier. In this work, the effects of three doses of dietary GML supplementation (150, 300, and 450 mg kg-1 hen) on the functional properties of EWP were investigated. The hardness of EWP gels was significantly improved by 300 and 450 mg kg-1 GML supplementation. Foaming capacity (FC) and foaming stability (FS) were increased after GML treatment; 450 mg kg-1 GML supplementation showed the most significant improvements, with 44.82% in FC and 23.39% in FS. Stabilization of EWP-oil emulsions was also improved, supported by a slowed creaming process and the formation of smaller oil droplets. The heat denaturation temperature and rheological properties were also modified by dietary GML supplementation, implying improved thermal stability. Our study demonstrated that GML supplementation has the potential to modify the functional properties of EWP, broadening the application of GML and providing a new perspective for evaluation of the efficacy of feed additives. © 2019 Society of Chemical Industry.

Formulation of oil-in-water emulsions for pesticide applications: impact of surfactant type and concentration on physical stability.

Oil-in-water (O/W) emulsions can be utilized as effective pesticide delivery systems in the agricultural industry. In this study, the effects of hydrophile-lipophile balance (HLB), concentration, and location of surfactants on the formation and physical stability of O/W emulsions suitable for pesticide applications was investigated using dynamic light scattering and vertical laser profiling. A non-polar pesticide (lambda-cyhalothrin) was used as a model. The pesticide emulsion with the highest stability was obtained using a commercial non-ionic surfactant (polyoxyethylene castor oil ether, EL-20) with a required HLB value of 10.5. Emulsion stability increased as the surfactant concentration was increased from 2 to 6%, which was attributed to the formation of smaller oil droplets during emulsification. Emulsions prepared with the surfactant initially in the oil phase were more stable than those prepared with it initially in the aqueous phase. The optimum formulation of the pesticide emulsion was determined as follows: 5% lambda-cyhalothrin (active ingredient) and 6% EL-20 (surfactant) dissolved in 5% S-200 (aromatic hydrocarbon, as oil phase), then deionized water up to 100%, which met the quality indicators set by the FAO standards. The present study is expected to provide useful information to improve the stability of pesticide emulsions for commercial applications.

Production of highly concentrated oil-in-water emulsions using dual-channel microfluidization: Use of individual and mixed natural emulsifiers (saponin and lecithin)

The fabrication of concentrated oil-in-water emulsions is useful for reducing storage and transportation costs, as well as for providing desirable textural, optical, stability, and release characteristics in commercial products. In this study, 50wt% oil-in-water emulsions were produced from natural emulsifiers using high-pressure dual-channel microfluidization (89.6MPa, 1 pass). The particle size and charge characteristics of emulsions stabilized using a hydrophilic biosurfactant (quillaja saponin) or mixtures of hydrophilic and hydrophobic biosurfactants (quillaja saponin+soy lecithin) were measured. The physical stability of the emulsions was determined during storage under quiescent conditions (pH7, 25°C). The mean droplet diameter and polydispersity decreased with increasing hydrophilic and hydrophobic biosurfactant concentration. Surface potential measurements indicated that interfacial composition depended on the amount of hydrophilic and hydrophobic biosurfactant present. The inclusion of hydrophobic emulsifier in the oil phase and hydrophilic emulsifier in the aqueous phase prior to homogenization, led to the formation of smaller oil droplets than using the hydrophilic emulsifier alone. The relatively small size and polydispersity of the droplets in the mixed-emulsifier systems led to a higher emulsion viscosity and a better aggregation stability, i.e., there was a smaller change in particle size during storage. However, some creaming was still observed in the emulsions due to the presence of a fraction of relatively large droplets. In summary, concentrated emulsions stabilized by mixed biosurfactants may be advantageous for commercial application in certain food, beverage, and pharmaceutical products.

Synergistic performance of lecithin and glycerol monostearate in oil/water emulsions

The effects of the combination of two low-molecular weight emulsifiers (lecithin and glycerol-monostearate (GMS)) on the stability, the dynamic interfacial properties and rheology of emulsions have been studied. Different lecithin/GMS ratios were tested in order to assess their impact in the formation and stabilization of oil in water emulsions. The combination of the two surfactants showed a synergistic behaviour, mainly when combined at the same ratio.The dynamic film properties and ζ-potential showed that lecithin dominated the surface of oil droplets, providing stability to the emulsions against flocculation and coalescence, while allowing the formation of small oil droplets. At long times of adsorption, all of the mixtures showed similar interfacial activity. However, higher values of interfacial pressure at the initial times were reached when lecithin and GMS were at the same ratio. Interfacial viscoelasticity and viscosity of mixed films were also similar to that of lecithin alone. On the other hand, emulsions viscosity was dominated by GMS.The synergistic performance of lecithin-GMS blends as stabilizers of oil/water emulsions is attributed to their interaction both in the bulk and at the interface.

Influence of lecithin on the processing stability of model whey protein hydrolysate‐based infant formula emulsions

Whey protein hydrolysate (WPH)‐based oil‐in‐water (O/W) emulsions containing lecithin (0–5%, w/w, oil) were produced and stored at 4 °C for 14 days. Surface tension and interfacial tension of these systems were measured for formulation development. Fat globule size distribution (FGSD) analysis and confocal laser scanning microscopy (CLSM) were used to assess the physical stability of emulsions during storage and identify mechanisms of instability. Lecithin decreased interfacial tension between oil and aqueous phases of model emulsions and allowed formation of smaller oil droplets on homogenisation. However, low‐intermediate levels (1–3%) of lecithin caused coalescence and shift to bimodal FGSD during storage of emulsions.

Formation of vitamin D nanoemulsion-based delivery systems by spontaneous emulsification: Factors affecting particle size and stability

Oil-in-water nanoemulsions are particularly suitable for encapsulation of lipophilic nutraceuticals because of their ability to form stable and transparent delivery systems with high oral bioavailability. In this study, the influence of system composition and preparation conditions on the particle size and stability of vitamin D nanoemulsions prepared by spontaneous emulsification (SE) was investigated. SE relies on the formation of small oil droplets when an oil/surfactant mixture is titrated into an aqueous solution. The influence of oil phase composition (vitamin D and MCT), surfactant-to-oil ratio (SOR), surfactant type (Tween 20, 40, 60, 80 and 85), and stirring conditions on the initial particle size of vitamin D nanoemulsions was studied. Nanoemulsions with small droplet diameters (d<200nm) could be formed using Tween 80 at SOR⩾1 at high stirring speeds (800rpm). These systems were relatively stable to droplet growth at ambient temperatures (<10% in diameter after 1month storage), but unstable to heating (T>80°C). The thermal stability of the nanoemulsions could be improved by adding a cosurfactant (sodium dodecyl sulphate (SDS)). The spontaneous emulsification method is simple and inexpensive to carry out and therefore has great potential for forming nanoemulsion-based delivery systems for food, personal care, and pharmaceutical applications.

Fundamental Aspects of the Science and Engineering of Oil Spill Dispersant Systems: An Overview of Recent Research Activities of the Gulf of Mexico Research Initiative-funded CMEDS Project

ABSTRACT Upon consideration of dispersant-related research, both before and after the Macondo Well oil release, it can be divided into two general categories: (1) the fundamentals of how dispersants work and the effects that may result from their use (e.g., physicochemical and transport characteristics of drops, bubbles, hydrates, surfactants), and (2) an applied focus that has emphasized the design of new dispersants or an enhancement of the performance of those products that are currently available. While there is an extensive amount of data relating to dispersants, a main focus has been on the demonstration of their effectiveness in bench tests and examination of the toxicity of dispersants and dispersed oil. As a result, there is a need for an enhanced understanding of dispersant and dispersed oil thermodynamics and their fate and transport, with a goal to translate the science and engineering to the development of new, effective dispersant systems. The focus of the work to be discussed addresses the following areas: Formation of small oil droplets: Widely dispersed stable oil droplets in the water column are easily accessible to microbes and therefore highly susceptible to degradation. It is important therefore, to understand the fundamental mechanisms of oil breakup and colloidal stabilization in order to develop new and effective dispersants. Dispersant-related processes under deep sea conditions: Current dispersants have been developed for surface spills. The efficacy of such formulations when applied at the high pressures and low temperatures representative of deep ocean release has not been systematically studied. Because of concomitant gas release at the discharge point, and the pressures involved, the liquid droplet is essentially a gas-expanded liquid which could behave quite differently when treated with dispersant components depending upon how they partition at the phase interfaces, i.e., gas/water, gas/oil, oil/water. Fluid mechanics of stabilized oil droplets: Droplet transport, as influenced by all thermodynamic variables of relevance under deep sea conditions, is being studied. Droplet interactions with solid particulates: A better understanding of these processes, either in marine sediments or in the water column, will help predict the environmental fate of the droplets. Development of alternative dispersants: Based on the knowledge gained with respect to the fundamentals, a key goal is the systematic translation of that understanding to the development of new and improved materials. This paper summarizes recent work of a collaborative research effort involving investigators from 22 universities, with particular emphasis on increasing the understanding of the science and engineering of oil spill dispersants.

Characterization and demulsification of solids-stabilized oil-in-water emulsions Part 1. Partitioning of clay particles and preparation of emulsions

Kaolinite clay particles treated with asphaltenes were used to study the partitioning of the clay particles between an oil-in-water emulsion and an aqueous phase. It was found that the interaction energy of the adsorbed particles and the equilibrium ratio of the clay concentration at the oil droplet surface to that in the bulk water were strong functions of the clay contact angle θ, for θ > 65°. For a given initial clay concentration in the bulk water and emulsification conditions, the variation of the oil droplet diameter with θ exhibited a minimum at θ ≈ 65°. Under similar emulsification conditions, a higher initial clay concentration in the bulk water resulted in the formation of smaller oil droplets and a larger volume of creamed emulsion.