Formulation of monodisperse oil‐in‐water emulsions loaded with ergocalciferol and cholecalciferol by microchannel emulsification: insights of production characteristics and stability

Nutritional deficiencies of ergocalciferol (VD₂) and cholecalciferol (VD₃) cause skeletal deformations. The primary aim of this study was to encapsulate VD₂ and VD₃ in food‐grade oil‐in‐water (O/W) emulsions by using microchannel emulsification (MCE). Silicon asymmetric straight‐through microchannel (MC) array consisting of 10 313 channels, each having an 11 × 104 μm microslot connected to a 10 μm circular microholes. 1% (w/w) sodium cholate or Tween 20 in water was used as the continuous phase, while 0.5% (w/w) of each VD₂ and VD₃ in different oils served as the dispersed phase. Monodisperse O/W emulsions with Sauter mean diameters of 28 to 32 μm and relative span factor widths below 0.3 were formulated via an asymmetric straight‐through MC array under appropriate operating conditions. The monodisperse O/W emulsions stabilised with Tween 20 remained stable for >30 days with encapsulation efficiencies (EEs) of VD₂ and VD₃ of above 70% at 4 and 25 °C. In contrast, those stabilised with sodium cholate had stability of >30 days with their EEs of over 70% only at 25 °C.     

Double emulsion (W/O/W) gel stabilised by polyglycerol polyricinoleate and calcium caseinate as mangiferin carrier: insights on formulation and stability properties

Mangiferin (MGF) is a phenolic compound isolated from mango, but its poor solubility significantly limits its use. In this study, MGF was embedded into the inner aqueous phase of W₁/O/W₂ emulsions. Firstly, the dissolution method of MGF was determined. MGF remained stable in solution with pH 13 at 30 min, and its solubility reached 10 mg mL⁻¹. When the pH of MGF solutions was adjusted from pH 13 to pH 6, MGF did not immediately crystallise, providing sufficient time to construct the MGF-loaded W₁/O/W₂ emulsions. Subsequently, the MGF-loaded W₁/O/W₂ emulsions were constructed using polyglycerol polyricinoleate (PGPR) and calcium caseinate (CAS). The formation and stability of the W₁/O/W₂ emulsions were investigated. The MGF-loaded W₁/O/W₂ emulsions stabilised with 1% PGPR and 1% – 3% CAS exhibited a low viscosity, limited loading capacity, and poor stability. Conversely, the MGF-loaded W₁/O/W₂ emulsions stabilised by 3%PGPR–3%CAS exhibited optimal loading capacity (encapsulation efficiency = 95.31% and loading efficiency = 0.91%) and stability, which was attributed to the fact that high viscosity and gel state retarded the migration of inner aqueous phase. These results indicated that the W₁/O/W₂ emulsions stabilised by PGPR and CAS may be a potential alternative for encapsulating mangiferin.     

Characterisation of emulsion properties and of interface composition in O/W emulsions prepared with hen egg yolk, plasma and granules

Comprehension of hen egg yolk emulsifying properties remains incomplete because competition between its various emulsifiers (proteins and lipoproteins containing phospholipids) has not been clearly elucidated and colloidal interactions between yolk-stabilised oil droplets have not been documented. Recent studies emphasised the interest of the fractionation of yolk into plasma and granules to improve this comprehension. In the present study, we characterised, concurrently, emulsion properties (oil droplet size and stability against creaming) and interface attributes (interfacial concentrations of proteins and phospholipids, SDS-PAGE profiles of adsorbed proteins and zeta potential) in oil-in-water (O/W) emulsions prepared with yolk, plasma and granules. We observed these features at four physicochemical conditions (pH 3.0 or 7.0 and at 0.15 or 0.55 M NaCl). Emulsion properties in emulsions made with yolk or plasma varied similarly as a function of pH and NaCl concentration whereas granules emulsions exhibited distinct properties. Therefore the main contributors to yolk emulsifying properties are to be sought for among plasma constituents (proteinaceous or phospholipids). Since, in plasma emulsions, variations of emulsion stability against creaming correlated exclusively to variations of protein interfacial concentration, a driving contribution of the proteinaceous part of plasma, namely apo-LDL, was hypothesised. In the pH and ionic strength ranges studied, zeta potentials of the interfaces were low, excluding extended electrostatic repulsion between oil droplets. We deduced that steric repulsion is the main interaction opposing to droplet aggregation in food emulsions made with yolk.     

Rheology: how to characterize and to predict the evolution of W/O/W multiple emulsions

The purpose of this work was to compare the evolution of three multiple emulsions (ME) by different controls. The series of water-in-oil-in-water (W/O/W) multiple emulsions were elaborated and controlled by both the usual analyses which permitted the classification of the multiple emulsions with respect to their thermal stability, and the rheological oscillatory and flow analyses which are polyvalent methods. Further, these allow the 'identity card' of the multiple emulsion to be drawn, its evolution to be followed, and moreover, its behaviour being foreseen by simulating ageing by shear. Three different behaviours are observed; a destructuration, a phase inversion and stability.     

Double emulsions (W/O/W): physical characteristics and perceived intensity of salty taste

This study addressed the correlation between physical characteristics of double emulsions and sensory perception, as the microstructure of these systems may provide the mechanism to understanding the initial cause of the altered salty taste. Thus, double emulsions (W/O/W) were prepared using different volumes of the internal aqueous phase while maintaining the same fat and sodium contents in the evaluated systems. Polyglycerol polyricinoleate (PGPR) and tween 80 were used as hydrophobic and hydrophilic emulsifiers, respectively. After preparation, the samples were stored at 25 °C for 4 days and submitted to analysis of optical microscopy, distribution and polydispersity of the oil droplets size, electrical conductivity, rheological behaviour and sensorial analysis. It was found that the use of different emulsifier concentrations (PGPR) did not influence the physical characteristics of the emulsions with the same formulation, but emulsions with different internal aqueous phase concentrations presented different results. These distinct characteristics may have influenced sensorial perception, as the emulsion with higher internal phase concentration was considered saltier. Thus, it can be concluded that structural differences of the double emulsions can be used to decrease the sodium contents without perceivable changes in salty taste.     

The effect of the type and the concentration of the lipophilic surfactant on the stability and release kinetics of the W/O/W multiple emulsions

Stable multiple emulsions that contain different lipophilic surfactants in the internal aqueous phase have been formulated. The multiple systems were assessed by evaluating several parameters such as macroscopic aspect, droplet size, percent release and accelerated stability under centrifugation or elevated temperature. The effect of polymeric and monomeric surfactants on the release mechanism and stability was examined. An excess of monomeric surfactant in the oil phase enhances the release rate and decreases stability. The release rate can be decreased by an increase of the lipophilic surfactant concentration. It appears that the more the oil globule swells, the less hydrosoluble drug is released. As a result a high swelling capacity is associated with better stability.     

O/W emulsion and W/O/W multiple emulsion: physical characterization and skin pharmacokinetic comparison in the delivery process of caffeine

The aim of this study was to compare the characteristics of an O/W emulsion and a W/O/W emulsion, formulated with similar ingredients. The physical properties of these two types of vehicles were characterized first. Using three types of in vitro models, human skin biopsies, nitrate acetate cellulose membranes and human reconstituted epidermis, the delivery potential of each vehicle for one hydrophilic drug, caffeine, was compared. The assessment of physical parameters, such as particle size, conductivity and rheological behavior enabled the nature of the test emulsions to be clearly identified. Clear differences were observed in the ability of each type of emulsion to deliver caffeine. Whatever the nature of the membrane used for the pharmacokinetic study, the absorption of caffeine was roughly two-fold lower (2.6 for human skin) when the W/O/W multiple emulsion was used as the vehicle. The concomitant determination of physical and kinetic properties of these two test emulsions allowed the W/O/W multiple emulsion and a simple O/W emulsion to be clearly differentiated.     

Droplet characterization and stability of soybean oil/palm kernel olein O/W emulsions with the presence of selected polysaccharides

Droplet characteristics, flow properties and stability of egg yolk-stabilized oil-in-water (O/W) emulsions as affected by the presence of xanthan gum (XG), carboxymethyl cellulose (CMC), guar gum (GG), locust bean gum (LBG) and gum Arabic (AG) were studied. The dispersed phase (40%) of the emulsions was based on soybean oil/palm kernel olein blend (70:30) that partially crystallized during extended storage at 5 °C. In freshly prepared emulsions, the presence of XG, CMC, GG and LBG had significantly decreased the droplet mean diameters. XG, LBG, GG and CMC emulsions exhibited a shear-thinning behavior but AG emulsion exhibited a Bingham plastic behavior and control (without gum) emulsion almost exhibited a Newtonian behavior. Both control and AG emulsions exhibited a severe phase separation after storage (30 days, 5 °C). The microstructure of stored XG emulsion showed the presence of partially coalesced droplets, explaining a large increase in its droplet mean diameters. Increases in droplet mean diameters and decreases in flow properties found for stored GG and LBG emulsions were attributed to droplet coalescence. Nevertheless, the occurrence of droplet coalescence in these emulsions was considered to be small as no free oil could be separated under centrifugation force. Increases in flow properties and excellent stability towards phase separation found for stored CMC emulsion suggested that CMC could retard partial coalescence. Thus, the results support the ability of CMC, GG and LBG in reducing partial coalescence either by providing a sufficiently thick continuous phase or by acting as a protective coating for oil droplets.     

Surface properties of phenolic compounds and their influence on the dispersion degree and oxidative stability of olive oil O/W emulsions

The surface and interfacial properties of gallic acid, catechin and quercetin, and their effect on the dispersion degree and the oxidative stability of olive oil oil-in-water (O/W) emulsions prepared using β-lactoglobulin and Tween 20 were studied.Gallic acid showed no effect on the surface properties while catechin was proven to be able to accumulate at the air/water interface, decreasing the surface tension values with increasing its concentration. All the phenolic antioxidants caused a decrease in the interfacial tension at the oil/water interface, even though only catechin and quercetin showed a concentration dependent behaviour.In emulsions, gallic acid did not affect the droplet size of the systems, catechin caused the formation of oil droplets bigger than those of the control, whilst quercetin improved the dispersion state of the emulsions with the increasing of its concentration. Gallic acid, despite its partitioning in the water phase due to its polarity, delayed the formation of both the hydroperoxides and TBARs and limited their accumulation. Catechin did not affect the formation of oxidation products whilst quercetin, among the tested antioxidants, caused the lowest formation of both hydroperoxides and TBARs through 33 days of storage.     

Effect of high pressure-treated wheat starch as a fat replacer on the physical and rheological properties of reduced-fat O/W emulsions

In the current research, the impact of high hydrostatic pressure-treated wheat starch (HPWS) at different concentrations (10%, 15%, and 20% w/w), as a fat replacer, on the physical, textural and rheological characteristics and stability of model reduced-fat emulsions (25%, 50%, and 75% fat reduction) was examined. Replacing a higher concentration of HPWS augmented the magnitude of zeta potential and decreased the Z-average droplet size and PDI values of the prepared samples, but increasing the fat reduction level (FR) revealed a reverse trend. The rheological analysis showed that HPWS caused an increase in G′ value of the emulsions rather than the control ones, and G′ increased significantly with increasing HPWS concentration, and tan δ decreased evidently, which depicts more solid-like behavior of prepared emulsions. Given results indicated that HPWS by creating comparable spreadability, consistency, elasticity, and yield stress, as well as good stability of the reduced-fat emulsions, can be suggested as a promising fat replacer.     

Verbascosides from olive mill waste water: assessment of their bioaccessibility and intestinal uptake using an in vitro digestion/Caco-2 model system

Olive mill wastewater (OMWW) is an agricultural waste material produced in high quantities in the Mediterranean basin. OMWW may be an inexpensive source of health promoting phytochemicals with potential economic value including many low molecular weight compounds such as verbascosides. While promising as antioxidants in vitro, little information is available on the potential absorption of verbascosides by humans. The main objective of the present study was to characterize the verbascoside content and potential for their bioavailability from a partially purified phenolic fraction (IP) of OMWW. The IP was obtained after ultrafiltration step at 5000 Dalton and gel filtration low-pressure chromatography (LH20) of OMWW. RP-HPLC analysis identified several soluble phenolics compounds including verbascoside and isoverbascoside as major components of OMWW fractions. The potential for bioavailability of these polyphenols was estimated by using both in vitro digestion and Caco-2 human intestinal cell models. In vitro digestive recoveries (bioaccessibility) were found to be 35.5%± 0.55% for verbascoside and 9.2% ± 0.94% for isoverbascoside highlighting potential sensitivity of these phenolics to gastric and small intestinal digestive conditions. Accumulation of verbascosides by highly differentiated Caco-2 monolayers was linear between 10 and 100 μM of verbascoside and isoverbascoside from IP extract. Uptake of verbascoside and isoverbascoside was rapid with peak accumulation occurring after 30 min with total accumulation efficiency of 0.1% and 0.2% providing intracellular levels of 130 and 80 pmol/mg cell protein for verbascoside and isoverbascoside, respectively. Combined, these data suggest that verbascosides present in OMWW are bioaccessible and provides a rationale for subsequent in vivo studies on the bioavailability and bioactivity of OMWW components.     

Dynamic oscillatory shear properties of O/W model system meat emulsions: Linear viscoelastic analysis for effect of temperature and oil concentration on protein network formation

Effects of oil concentration (57.50%, 58.75%, 60.00% and 61.25%) and temperature (5, 10 and 15 °C) on O/W model system meat emulsions were analyzed using oscillatory dynamic shear tests, allowing all emulsion systems to be characterized as linear viscoelastic solids exhibiting a pseudoplastic flow. The emulsion systems were characterized as weak gel-like macromolecular dispersions with G′ much greater than G″, exhibiting a plateau region. A modified Cox-Merz rule was applicable using shift factors. Frequency dependence of complex modulus (G^∗) was studied to measure strength of cross-linking protein network of the emulsion systems by calculating a practically constant order of the relaxation function (α = 0.10) and a concentration dependent stiffness parameter (A_α) using Friedrich and Heymann theory. It was concluded that the viscoelastic characteristics and strength of the emulsion systems increased with increasing oil level, but decreased with temperature. Different mathematical models were successfully constructed to predict the rheological parameters.     

Study of commodity properties of food emulsions Part 1. The effect of dispersion medium composition on kinetic stability of O/W emulsions containing proteins,acidic polysaccharides and calcium salts

The effect of concentrations of acidic polysaccharide and calcium ions on the kinetic stability, viscosity and dispersity of protein-containing O/W emulsions is studied. Variation of kinetic stability of the emulsions studied is independent of dispersion composition. In a wide range of calcium acetate concentrations a correlation is observed between kinetic stability and viscosity of emulsions at sodium alginate concentration in the dispersion medium ≤ 0.3%. The transition zone between liquid solution and gel is widened in the presence of sodium caseinate. Maximum kinetic stability is reached at calcium acetate: sodium alginate concentrations of 1.0-1.2 and ～ 6.0, corresponding to optimum conditions for formation of homogeneous crosslinked structures of calcium alginate and calcium caseinate.     

Influence of pH on linear viscoelasticity and droplet size distribution of highly concentrated O/W crayfish flour-based emulsions

In the present work, the influence of pH on stability of oil-in-water (O/W; 75 wt%/25 wt%) emulsions stabilized by crayfish flour (CF) has been studied. CF (containing ca. 65 wt%) showed poor functionality in a wade range of pH, which inhibits formation of stable emulsions. An indirect procedure has been developed in order to obtain emulsion at a broad pH range, including isoelectric point (pI) value. The emulsions have been characterized by means of linear dynamic viscoelasticity and droplet size distribution (DSD) analysis. These emulsions present a behaviour characteristic of highly concentrated emulsions with a well-developed plateau region. The most unfavourable DSD and linear viscoelastic results correspond to the pI. A significant improvement takes place as the pH value departs from the pI. An exception for linear viscoelasticity results have been found at pH 10, which is close to the pI for rod segments of myofibrillar proteins. Stability of these emulsions has been studied by following the evolution of DSD and linear viscoelastic parameters along time. The poorer results in emulsion stability correspond to pH values close to the pI, at which the increase in droplet size or uniformity parameter as well as the decrease in the plateau modulus become more pronounced. Conversely, the stability significantly improves as the pH departs from pI.     

Influence of chitosan concentration on the stability,microstructure and rheological properties of O/W emulsions formulated with high-oleic sunflower oil and potato protein

Relatively concentrated (40 wt%) O/W emulsions formulated with high-oleic sunflower oil as disperse phase, potato protein isolate as emulsifier and chitosan as stabiliser were prepared by rotor–stator/high-pressure valve/rotor–stator homogenization. The influence of chitosan concentration on the physical stability of emulsions was studied in (0.25–1) wt% range by visual inspection, rheological and microstructural techniques. Steady shear flow curves were sensitive to the occurrence of creaming upon the rise of zero-shear viscosity values. The effect of increasing concentration of chitosan on the zero-shear viscosity turned out to be dependent on emulsion ageing and always resulted in a stepwise increase of the critical shear rate for the onset of shear thinning flow. The critical oscillatory shear stress for the onset of non-linear viscoelastic behaviour was more sensitive than the critical shear rate to detect creaming in emulsions. Mechanical spectra are definitely demonstrated to be the most powerful tool to detect not only creaming but also oil droplet flocculation on account of changes in the plateau relaxation zone. CSLM micrographs supported the interpretation of dynamic viscoelastic results, especially when flocculation as well as coalescence took place. Cryo-SEM micrographs evidenced the formation of increasingly denser protein–polysaccharide networks with chitosan concentration and the fact that the latter governs the microstructure of the emulsion when reaches 1 wt% concentration promoting enhanced physical stability.     

Concentrated O/W emulsions formulated by binary and ternary mixtures of sodium caseinate,xanthan and guar gums: rheological properties,microstructure, and stability

Food Science and Biotechnology - The effects of xanthan gum (XG) (0, 0.3, 0.6 wt%), guar gum (GG) (0, 0.3, 0.6 wt%) and XG:GG mixtures (0.3–0.3, 0.3–0.6, 0.6–0.3 and 0.6–0.6...