Crystals and crystallization in oil-in-water emulsions: Implications for emulsion-based delivery systems (original) (raw)
Related papers
Journal of the American Oil Chemists' Society, 2008
The objective of this research was to systematically study the effect of processing conditions on the crystallization behavior and destabilization mechanisms of oil-in-water emulsions. The effect of crystallization temperature (T c) and homogenization conditions on both thermal behavior and destabilization mechanisms were analyzed. Results show that the crystallization of lipids present in the emulsions was inhibited when compared with bulk lipids as evidenced by a lower onset and peak temperature (T on and T p , respectively) in differential scanning calorimetry crystallization exotherms. The smaller the droplet size in the emulsion, the more significant the inhibition (lower T on and T p). Lower values of T on and T p were not necessarily indicators of emulsion stability. Homogenization conditions not only affected the T on and T p of crystallization but also the crystallization profile of the samples. Lipids present in emulsions with small droplets were crystallized and melted in a less fractionated manner when compared to lipids in bigger droplets or even to the bulk lipids. The amount of lipid crystallized as evidenced by enthalpy values, did not have a direct relationship with the emulsions stability. Although enthalpy values increased as T c decreased, the destabilization kinetics did not follow the same tendency as evidenced by back scattering measurements.
2017
Flaxseed oil has abundant polyunsaturated fatty acids that are important to health but are oxidized easily during storage. These bioactive lipids are susceptible to chemical deterioration causing nutrient loss and development of undesirable off-flavors. Oil-in-water emulsions could be used as an effective tool to protect these functional active lipids from degradation by engineering the emulsion droplet interfacial layer. Engineering oil/water interfaces of emulsions has been studied extensively, but practical technologies are still demanded by the food industry. Emulsions are a category of encapsulation systems applicable to various bioactive compounds in food formulations. Emulsions have a fluidic oil phase which facilitates the mobility and release of bioactive compounds. Emulsion based encapsulation systems has been exhibited to have potential applications in functional food formulation. They have been used to inhibit lipid oxidation, triggered or controlled release during diffe...
Water-in-triglyceride oil emulsions. Effect of fat crystals on stability
Journal of The American Oil Chemists Society, 1995
The influence of low concentrations (0.1-5%) of fat crystals on the stability of water-in-soybean oil emulsions was examined by light scattering and sedimentation experiments. Both the initial flocculation/coalescence rate and long-term stability against water separation were determined. The initial flocculation/coalescence rate increased upon addition of small amounts of fat crystals. When the crystal concentration was increased above a critical concentration (specific to a system), a decrease in the flocculation/coalescence rate occurred. The increased flocculation/coalescence rate is likely the effect of bridging of water droplets by fat crystals. Fat crystal wetting by water is an important criterion for this phenomenon to occur. Emulsion stabilization for crystal concentrations above critical is caused by a mechanical screening of water droplets. The presence of considerable amounts of crystals in oil also lowered the density difference between droplet and medium, and enhanced viscosity. The degree of increase in viscosity depended upon the emulsifier. Both a decrease in density difference and an increase in viscosity play a role in hindering flocculation/coalescence of droplets. In long-term studies of water separation, all concentrations of fat crystals stabilized the water-in-oil emulsions. The droplet size of these emulsions increased until the critical droplet size was approached where the screening effect of crystals on the droplets no longer stabilized the emulsions. The stabilizing effect for emulsions with monoolein was continuously improved by increasing the amount of crystals up to 5%. For lecithin-stabilized emulsions, an optimal effect was achieved for fact crystal concentrations of 1–2%.
Encapsulation of Lipid-Soluble Bioactives by Nanoemulsions
Molecules, 2020
Lipid-soluble bioactives are important nutrients in foods. However, their addition in food formulations, is often limited by limited solubility and high tendency for oxidation. Lipid-soluble bioactives, such as vitamins A, E, D and K, carotenoids, polyunsaturated fatty acids (PUFA) and essential oils are generally dispersed in water-based solutions by homogenization. Among the different homogenization technologies available, nanoemulsions are one of the most promising. Accordingly, this review aims to summarize the most recent advances in nanoemulsion technology for the encapsulation of lipid-soluble bioactives. Modern approaches for producing nanoemulsion systems will be discussed. In addition, the challenges on the encapsulation of common food ingredients, including the physical and chemical stability of the nanoemulsion systems, will be also critically examined.
Non-Aqueous Emulsion: Versatile Vehicle For Drug Delivery
Pharmaceutical …
The delivery of poorly water-soluble drugs has been the subject of much research, as approximately 40% of new chemical entities are hydrophobic in nature. One area in which published literature is lacking is the field of nonaqueous emulsions.
Journal of Cosmetics, Dermatological Sciences and Applications
A moisturizing cream containing 25 wt% of an organic solvent, diethylene glycol monoethyl ether (DEGEE), is observed to be stabilized by an emulsifying wax blend of cetearyl alcohol, dicetyl phosphate, and ceteth-10 phosphate (tradename Crodafos CES). Polarized light microscopy indicates that the Crodafos CES helps to produce a liquid-crystal stabilized oil-in-water emulsion, which is physically stable for months under accelerated aging conditions and chemically stable over the full topical pH range of 3.5 to 9. Emulsion globule size in the cream is observed to be dependent on the degree of emulsifying wax neutralization, with the globule size decreasing with increasing cream pH. The superior solubilizing properties of DEGEE combined with the full pH range and liquid-crystal stabilizing properties of the Crodafos CES give this formulation the potential for a wide range of applications in the topical delivery of active pharmaceutical ingredients.
Formulation and Development of Non-Aqueous Emulsion
The delivery of poorly water-soluble drugs has been the subject of much research, as approximately 40% of new chemical entities are hydrophobic in nature. One area in which published literature is lacking is the field of non-aqueous emulsions and some researchers have used polyethylene glycol (PEG) as a continuous phase for such emulsions (1-6). The nature of this emulsion will allow capsule filling at a later stage. In the present study, an attempt has been made to develop non-aqueous emulsions of the type oil-in-PEG suitable for drug loading.
International Journal of Applied Pharmaceutics, 2019
Objective: Parameters in the oil pre-concentrate which can affect the solvent capacity of the resultant dispersion such as, oil-cosurfactant ratio, type of surfactant used in the system, the inclusion of water soluble co-solvents and the solubilization capacity of native surfactants such as, bile salts and lecithin were studied in an attempt to circumvent crystallization of drug during its passage in the gut.Methods: Different types of self-emulsifying systems representing type II, IIIA and IIIB, were used to probe the influence of the various physicochemical properties of the resultant dispersions on the fate of dissolved model lipophilic drug. This was achieved by studying emulsification behavior of lipid systems in fed and fasted biological fluids, analyzing solubilization/drug crystallization kinetics and oil droplet diameter measurement.Results: Self-micro-emulsifying lipid systems lost solvent capacity on dispersion and were not able to keep the drug in solution at equilibrium...
Food Research International, 2013
The effect of selected monoglycerides on droplet morphology and rheology of palm kernel oil emulsions was studied. Combination of lactic acid ester of monoglycerides (LACTEM) and unsaturated monoglycerides (GMU) yielded highly viscous emulsions caused by partial coalescence. LACTEM combined with saturated monoglycerides (GMS) or diacetyl tartaric acid ester of monoglycerides (DATEM) gave low-viscous emulsions. The rheological behavior was found not to be related to polymorphic transformations of fat in the emulsions. A possible relationship between structural changes of emulsions and the effect of monoglyceride crystallization behavior of PKO was examined by studying the monoglycerides' influence on crystallization of bulk PKO. Polymorphic transformation, crystallization kinetics and melting/crystallization profile of bulk PKO were analyzed. The monoglycerides had minor effect on crystallization behavior of bulk PKO compared to the major impact on emulsion stability. This indicates that emulsifiers act differently in bulk and dispersed fat. For PKO the structural changes of the emulsions were independent of the effects of monoglycerides on the crystallization of bulk fat.