Lecithin-stabilized Emulsions Research Articles

Plant-Based Oil-in-Water Food Emulsions: Exploring the Influence of Different Formulations on Their Physicochemical Properties.

The global focus on incorporating natural ingredients into the diet for health improvement encompasses ω-3 polyunsaturated fatty acids (PUFAs) derived from plant sources, such as flaxseed oil. ω-3 PUFAs are susceptible to oxidation, but oil-in-water (O/W) emulsions can serve to protect PUFAs from this phenomenon. This study aimed to create O/W emulsions using flaxseed oil and either soy lecithin or Quillaja saponins, thickened with modified starch, while assessing their physical properties (oil droplet size, ζ-potential, and rheology) and physical stability. Emulsions with different oil concentrations (25% and 30% w/w) and oil-to-surfactant ratio (5:1 and 10:1) were fabricated using high-pressure homogenization (800 bar, five cycles). Moreover, emulsions were thickened with modified starch and their rheological properties were measured. The physical stability of all emulsions was assessed over a 7-day storage period using the TSI (Turbiscan Stability Index). Saponin-stabilized emulsions exhibited smaller droplet diameters (0.11-0.19 µm) compared to lecithin (0.40-1.30 µm), and an increase in surfactant concentration led to a reduction in droplet diameter. Both surfactants generated droplets with a high negative charge (-63 to -72 mV), but lecithin-stabilized emulsions showed greater negative charge, resulting in more intense electrostatic repulsion. Saponin-stabilized emulsions showed higher apparent viscosity (3.9-11.6 mPa·s) when compared to lecithin-stabilized ones (1.19-4.36 mPa·s). The addition of starch significantly increased the apparent viscosity of saponin-stabilized emulsions, rising from 11.6 mPa s to 2117 mPa s. Emulsions stabilized by saponin exhibited higher stability than those stabilized by lecithin. This study confirms that plant-based ingredients, particularly saponins and lecithin, effectively produce stable O/W emulsions with flaxseed oil, offering opportunities for creating natural ingredient-based food emulsions.

Comparative effects of micro vs. submicron emulsions on textural properties of myofibrillar protein composite gels

This study aimed to investigate the impact of emulsion particle size (micro vs. submicron) on the physicochemical and rheological properties of myofibrillar protein (MP) gels. MP-based oil-in-water micro-emulsions (∼2,091 nm) and submicron-emulsions (∼522 nm) were compared with each other and with lecithin-stabilized micro-emulsions (∼1,330 nm) and submicron-emulsions (∼543 nm). Emulsion particle size, ζ-potential, and morphological properties using transmission and confocal microscopies) were measured. Additionally, dynamic rheological behavior, mechanical strength, water-holding capacity (WHC), water mobility, and protein secondary structures of the emulsion gels containing 2.5% protein and 5% oil) were analyzed. The results showed that emulsion droplet size had no significant effect on gel strength and storage modulus, regardless of the surfactants used. However, the MP-coated submicron-emulsion exhibited a greater improvement in gel WHC (p < 0.05) compared to its micro-emulsion counterpart. Overall, emulsion gels displayed greater strength than oil-free control gels. MP-based emulsions proved more effective than lecithin-stabilized emulsions in modifying the gelling properties, primarily due to the formation of a visible interfacial protein film that prevented oil droplet aggregation. Based on these findings, protein-based emulsions were preferred over lecithin-based emulsions, with MP submicron-emulsions offering the advantage of enhanced moisture retention in cooked MP gels.

Emulsifiers modulate the extent of gastric lipolysis during the dynamic in vitro digestion of submicron chia oil/water emulsions with limited impact on the final extent of intestinal lipolysis

Consumer demands for healthier foods are constantly on the rise and results in the diversification of sources such as vegetable oils. Chia oil is a relevant source of α-linolenic acid. One of the targeted applications is the inclusion of chia oil in emulsified form in beverages where it is necessary to obtain stable submicron emulsions, acting as carrier of nutrients such as lipids. In the present work, high-pressure homogenization was employed to produce emulsions (10% chia oil) with small oil droplets (300 nm), formulated with different emulsifiers (beta-lactoglobulin (BLG), lecithin and Tween 80). These emulsions were submitted to a dynamic in vitro digestion (DIDGI) to better understand the main mechanisms involved in the process of lipolysis, in order to design systems that may allow the modulation of the digestive action of lipases, thus ensuring the maximum bioaccessibility of the lipids. This device mimics part of the transient biochemical conditions as well as the flow of foods through the different compartments occurring in the real digestion. Significant differences were observed in the lipolysis during the gastric phase. BLGemulsions reached a lipolysis degree of 30%. Lecithin-stabilized emulsions behave similarly to BLG ones during the first 90 min but lipolysis levelled off further ∼20%. Finally, Tween-80-stabilized emulsions remained almost undigested (around 2%). No significant differences were noticed in duodenum and distal small intestine, irrespective of the emulsifier employed. After digestion, the fatty acid bioaccessibility was higher with BLG as emulsifier.

In-vitro digestion of whey protein- and soy lecithin-stabilized High Oleic Palm Oil emulsions

Sweet whey- and soy lecithin-stabilized emulsions have been studied as potential delivery systems of High Oleic Palm Oil bioactive compounds. However, the gastrointestinal behavior of these systems has not been investigated. In this work, two High Oleic Palm Oil emulsions were submitted to in vitro digestion using a standardized static method. Stability of the emulsions was followed in each digestive phase and the final extent and kinetics release as well as the bioaccessibility of free fatty acids were measured and compared against non-encapsulated control. No changes were found in the droplet size of the emulsion after oral digestion, however, during gastric digestion, destabilization was observed due to the pH and the ionic strength of the medium. During the intestinal phase, nanoemulsions showed the highest rate constant followed and the least free fatty acids release final extent (78.48 ± 3.08 wt%) in comparison with macroemulsions (86.06 ± 2.04 wt%) and control (107.77 ± 1.45 wt%). Saturated fatty acids showed lower bioaccessibility in both emulsions than for control, meanwhile it increased for unsaturated ones. The results obtained allow addressing future research in formulation and design of delivery systems to improve the High Oleic Palm Oil digestibility and bioactive compounds bioaccessibility.

Phospholipid composition and emulsifying properties of rice bran lecithin from enzymatic degumming

The phospholipid composition and emulsifying properties of rice bran lecithin recovered from enzymatic degumming catalyzed by phospholipase A1 (PLA1) were investigated and comparing to those from citric acid and water degumming. Rice bran lecithin from enzymatic degumming (RLED) had a different phospholipid composition compared with that from water and citric acid degumming, with a particularly high lysophospholipid concentration. Meanwhile, PLA1 showed hydrolysis selectivity for phosphatidylcholine and phosphatidylethanolamine, but almost no selectivity for phosphatidylinositol. RLED provided better emulsion stability compared with rice bran lecithin from citric acid degumming (RLCD) and water degumming (RLWD). RLED-stabilized emulsions exhibited smaller particle sizes when deionized water or phosphate buffer were used as the aqueous phase, compared with RLCD and RLWD-stabilized emulsions. RLED, RLCD, and RLWD-stabilized emulsions had similar shear stresses when using phosphate buffer as the aqueous phase, and lower shear stresses when using deionized water. Furthermore, the apparent viscosity was higher when using phosphate buffer as the aqueous phase. Meanwhile, the microstructure of rice bran lecithin-stabilized emulsions corresponded with their particle size distribution and viscosity. This information will help food industry to evaluate the potential applications of RLED.

Modulation of caseinate-stabilized model oil-in-water emulsions with soy lecithin.

Demands for plant-based food and beverage products have escalated in recent years. However, many commercial coffee creamers are still being made using dairy derivatives such as sodium caseinate. Therefore, there is a need to investigate the replacement of dairy based proteins with plant-based alternatives. This study was carried out to systematically investigate the properties of model O/W emulsions stabilized by either sodium caseinate (0.25 to 1.5%) or soy lecithin (0.5 to 1.5%). The model emulsions were made of 10% medium chain triglyceride (MCT) oil-in-water emulsions at pH 7. All model O/W emulsions exhibited whitish appearances similar to that of commercial creamers and were effective at lightening black coffee, except those containing the lowest emulsifier concentrations i.e., 0.25% caseinate or 0.5% lecithin. The lightness of the model emulsions depended on the type and level of emulsifier used, with soy lecithin-stabilized emulsions having similar lightening power compare to that stabilized by sodium caseinate. No feathering or free oil were observed in the whitened coffees at the highest emulsifier level used. Mixtures of caseinate and lecithin emulsifiers were also used and model O/W emulsions with similar physical properties to that stabilized by sodium caseinate alone were produced. The mixed emulsifier-stabilized model emulsions had similar lightness when added to coffee than those stabilized by the individual emulsifiers, suggesting similar stabilization mechanisms using these emulsifiers alone or in combination.

The Effect of Sodium Carboxymethylcellulose on the Stability and Bioaccessibility of Anthocyanin Water-in-Oil-in-Water Emulsions

Water-in-oil-in-water (W1/O/W2) emulsions provide protective encapsulation to plant bioactive compounds in food matrix and under gastrointestinal conditions. However, the stability of the emulsions during the storage is crucial for their use in the food industry. Hence, the aim of this study was to enhance the stability and bioaccessibility of W1/O/W2 emulsions containing anthocyanins with the use of sodium carboxymethylcellulose (CMCNa). The emulsions were prepared by ultrasound technology, adding polyglycerol polyricinoleate (PGPR) in the inner aqueous phase of emulsions, and lecithin and Tween 20 in the outer aqueous phase. The systems were physicochemical characterized over the time and their behavior under simulated gastrointestinal conditions was investigated. Our results showed high encapsulation efficiencies above 90% and an increase in bioaccessibility with the use of CMCNa. Moreover, the polymer addition slowed down the free fatty acid release and increased the oil digestibility of lecithin-stabilized emulsions. These latter emulsions presented the highest bioaccessibility (31.08 ± 1.73%), the more negative values of ζ-potential and no variations on the particle size and the backscattering profile over the time, thus being the most stable emulsions. These results provide useful information for the design of anthocyanin emulsion-based delivery systems to guarantee their functionality in food matrices as well as through the gastrointestinal tract.

Emulsifier Dependent in vitro Digestion and Bioaccessibility of β-Carotene Loaded in Oil-in-Water Emulsions

This study was performed to examine the effect of emulsifiers used to coat emulsion droplets containing β-carotene on the behavior of lipid digestion and bioaccessibility. Different emulsifiers (whey protein isolate, soy protein isolate, sodium caseinate, Tween 20, and soy lecithin) were used to prepare emulsions with similar sized droplets (200–400 nm). Protein-stabilized emulsions showed a similar behavior of digestion, and morphological change in the simulated gastrointestinal conditions. Soy lecithin-stabilized emulsions showed the lowest rate and extent of lipid digestion probably due to the low emulsifying capability of soy lecithin, showing coalesced droplets occurring after exposure to the gastric phase. Tween 20-stabilized emulsions had a lower rate and extent of lipid digestion than that of protein-stabilized emulsions, even though Tween 20-stabilized emulsions had a more stable structure to resistant to aggregation in gastric phase. Even though the difference in the digestion rate and extent, β-carotene bioaccessibility was not significantly different among emulsions stabilized by different emulsifiers at p < 0.05.

Physicochemical properties and digestibility of emulsified lipids in simulated intestinal fluids: influence of interfacial characteristics

An improved understanding of the behaviour of lipids within the gastrointestinal tract will facilitate the structural design of foods that provide specific physiological responses. In this work, we studied the influence of interfacial characteristics (emulsifier type and surface area) on the behaviour of emulsified lipids within a simulated small intestine (duodenum). Pluronic F68-stabilized emulsions were more resistant to lipid digestion than lecithin-stabilized emulsions. Interfacial tension, droplet charge (ζ-potential), and microstructure measurements were used to identify the physicochemical origin of this effect. Pluronic F68 was shown to be more difficult than lecithin to displace from lipid droplet surfaces by bile salts and lipase arising from the duodenal juice. Specifically, duodenal components decreased the interfacial tension of a Pluronic-covered interface to a lesser extent, as compared to the interface covered by lecithin. These results demonstrate that the properties of the interfacial layer surrounding lipid droplets can be designed to modulate the lipid digestion process. This knowledge is critical for the rational development of delivery systems for food and pharmaceutical applications that can control the uptake of lipids and lipid-soluble components under physiological conditions.

Effect of lipid type on water‐in‐oil‐emulsions stabilized by phosphatidylcholine‐depleted lecithin and polyglycerol polyricinoleate

Water-in-oil (W/O, 30:70) emulsions were prepared with phosphatidylcholine-depleted lecithin [PC/(PI,PE) = 0.16] or polyglycerol polyricinoleate (PGPR) as emulsifying agents by means of pressure homogenization. The effect of lipid type (medium-chain triacylglycerols, sunflower, olive, butter oil, or MCT-oil/vegetable fat blends) was investigated in relation to particle size distribution, coalescence stability and the sedimentation of the water droplets. A significant correlation (p <0.05) was observed between the interfacial pressure caused by the addition of lecithin to the pure lipids and the specific surface area of the emulsion droplets (rs = 0.700), and between the viscosity of the lipids used as the continuous phase (reflecting the fatty acid composition) and the specific surface area of the emulsion droplets (rs = 0.8459) on the other hand. Blends of vegetable fat and MCT-oil led to reduced coalescence stability due to the attachment of fat crystals to the emulsion droplets. Lecithin-stabilized W/O emulsions showed significantly higher viscosities compared to those stabilized with PGPR. It was possible to adjust the rheological properties of lecithin-stabilized emulsions by varying the lipid phase.

Rheology and stability of acidified food emulsions treated with high pressure.

The stability and rheology of acidified model oil-in-water emulsions (pH 3.6 +/- 0.1) were evaluated before and after high-pressure treatments. Varying concentrations of canola oil (0-50% w/w), whey protein isolate, polysorbate 60, soy lecithin (0.1-1.5% w/w each), and xanthan (0.0-0.2% w/w) were chosen. Exposure to high pressures (up to 800 MPa for 5 min at 30 degrees C) did not significantly affect the equivalent surface mean diameter D[3,2], flow behavior, and viscoelasticity of the whey protein isolate and polysorbate 60-stabilized emulsions. Pressure treatments had negligible effects on emulsion stability in these systems, except when xanthan (0.2% w/w) was present in which pressure improved the stability of polysorbate 60-stabilized emulsions. Soy lecithin-stabilized emulsions had larger mean particles sizes and lower emulsion volume indices than the others, indicating potential instability, and application of pressure further destabilized these emulsions.

Effect of emulsifier on oxidation properties of fish oil-based structured lipid emulsions.

The effects of the emulsifiers lecithin, Tween 20, whey protein isolate, mono-/diacylglycerols, and sucrose fatty acid ester on oxidation stability of a model oil-in-water emulsion prepared with enzymatically synthesized menhaden oil-caprylic acid structured lipid were evaluated. Oxidation was monitored by measuring lipid hydroperoxides, thiobarbituric acid reactive substances, and the ratio of combined docosahexaenoic acid (DHA) and eicosapentaenoic acid (EPA) contents to palmitic acid in the emulsion. After high-pressure homogenization, all emulsions, except those prepared with lecithin, had similar droplet size distributions. All structured lipid emulsions, except for the lecithin-stabilized emulsions, were stable to creaming over the 48-day period studied. Emulsifier type and concentration affected oxidation rate, with 0.25% emulsifier concentration generally having a higher oxidation rate than 1% emulsifier concentration. Overall, oxidation did not progress significantly enough in 48 days of storage to affect DHA and EPA levels in the emulsion.

Detrimental effect of excess lecithin on the stability of fluorocarbon/lecithin emulsions

The formation and stability of concentrated lecithin-stabilized emulsions of perfluorodecalin (100% and 70% w/v, i.e. 51.5% and 36.1% v/v) have been studied for lecithin/fluorocarbon ratios ranging from 2 to 11. The stability was found to go through a maximum for a lecithin/fluorocarbon ratio of 4-6%

Stability of lecithin-stabilized emulsions in the presence of sucrose or hydroxyethylcellulose

The stability of lecithin-stabilized oil-in-water emulsions as a function of oil phase volume fraction in the range 0.011–0.766 was checked by studying creaming and measuring distribution of droplet diameter at ages between 1 day and 6 months. Emulsions with lower oil volume fractions were found to be more flocculated (and then creamed faster) but more stable towards coalescence than emulsions with higher oil volume fractions. The effects of adding sucrose or a non-gelling polymer (hydroxyethylcellulose) in the aqueous phase were studied over a 1 month period. The addition of sucrose improved stability of the emulsions towards coalescence, flocculation and creaming, whereas the addition of polymer improved stability towards coalescence but led to a net increase in the degree of flocculation and then a destabilization versus creaming. These results could be related to a depletion phenomenon in the emulsions in the presence of polymer.

The role of calcium ions and bile salts on the pancreatic lipase-catalyzed hydrolysis of triglyceride emulsions stabilized with lecithin.

Lecithin-stabilized triglyceride emulsions are subject to hydrolysis by pancreatic lipase. The time profiles of these reactions are characterized by a lag-phase and a zero-order phase. Lag phases are more pronounced with long-chain triglycerides. Ca2+ is effective in reducing the lag-phase and activating lipase. Kinetic analysis of the reactions suggests that, like previous findings by others, taurodeoxycholate (TDC) micellar solutions combine with the lipase-colipase complex to form another catalytically active enzyme form. This enzyme form exhibits reduced activity in the absence of Ca2+. In the presence of Ca2+ the mixed micelle-lipase complex becomes more active and opens a new pathway for lipolysis. It is suggested that this enzyme form can bind more easily to interfaces with different physicochemical properties. Under these conditions, Ca2+ activates the lipolysis of short-, medium-, and long-chain triglycerides by a similar mechanism. Maximum activities were measured in the presence of approximately 6 mM TDC and 30 mM Ca2+. The experimental conditions approximate the physiological conditions in the gastrointestinal tract since all of the factors studied here have been reported to be necessary for in vivo lipolysis and/or absorption of triglycerides. A mechanistic model for lipolysis in the presence of Ca2+ and the bile salt TDC is proposed which accounts for most of the experimental observations in a quantitative manner.