Verica J. Sovilj

Influence of polymer-surfactant interactions on o/w emulsion properties and microcapsule formation.

The aim of this work was to investigate the influence of interactions between 1.00%w/w hydroxypropylmethyl cellulose (HPMC) and the anionic surfactant sodium dodecylsulfate (SDS) on the properties of 20%w/w sunflower oil/water emulsion and the corresponding microcapsules obtained by spray drying technique. On the basis of the viscosity and rheological measurements, particle size and particle size distribution, and stability assessment, it was concluded that the emulsion characteristics depend strongly on the interaction mechanism. Significant increase in viscosity and non-Newtonian thixotropic behavior was observed in the SDS concentration range from 0.15 to 1.00%w/v, corresponding to HPMC-SDS interactions in the continuous phase. In the interaction region, a three-dimensional network is formed in the continuous phase by intermolecular binding of SDS molecules to the adjacent HPMC chains, which contributes to increase in the viscosity and thixotropic properties. The mean diameter of emulsion particles, d(vs), decreases with increase in SDS concentration, but emulsion stability depends on the adsorption layer structure, i.e. HPMC-SDS interactions. The HPMC/SDS complex adsorbed at the o/w interface makes the layer more compact, enhancing thus emulsion stability. Microcapsules, obtained in the form of powder by spray drying of emulsions, have good redispersibility in water, but their stability changes depending on the HPMC-SDS interaction mechanism, i.e., the HPMC/SDS complex forms a more compact layer that is resistant to breaking during the drying process. The highest encapsulation efficiency was found in the interaction region.

Action of emulsifiers during homogenization of o/w emulsions

Droplet size and size distribution changes at homogenization of paraffin oil emulsions, stabilized by different concentrations of various emulsifiers, were investigated. During homogenization, samples were taken from emulsions and the most frequently occuring diameter, mean droplet diameter and standard deviation (distribution width) were determined. Mathematical relations describing changes of mean diameter and distribution width, as a function of the homogenization period and emulsifier concentration, were derived and applied to the experimental data. Emulsifier efficiencies and capabilities were characterized by physical constants and graphically. Optimal homogenization time interval, optimal emulsifier concentrations and corresponding droplet size distribution parameters were computed.

Composition of Essential Oil Obtained From Tubular, Head and Ligulate Flowers of Calendula officinalis L. by Steam Distillation of Plant Material and CO2 Extracts

Abstract Essential oil content of tubular, head and ligulate flowers of Calendula officinalis L. were determined using official steam distillation procedure. It was found that the ligulate flower sample had the highest oil content (0.16%). Applying SFE by means of CO2 (200 bar, 40°C, 3 h extraction time), the highest extraction yield was found in tubular and ligulate flower samples (3.67% and 3.64%). Head flower had a lower extraction yield (2.60%) as the result of relatively small content of fatty oil, waxes and resins present in plant material. Steam distillation procedure was applied to obtain essential oils from the CO2 extracts devoid from cuticular waxes and resins. The compositions of oils were determined by GC and GC/MS. The main compounds of all investigated oils were α-cadinol (11.7–29.1%), δ-cadinene (3.2–20.3%), γ-cadinene (1.5–11.4%) and cadina-3,9-diene (0.4–11.2%). The oil samples obtained from the CO2 extracts were found to be more complex containing α-gurjunene, β-caryophyllene, β-gurjunene, cis-muurola-4(14)-5-diene and α-humulene.

Preparation and Characterization of Oil Containing Microcapsules Obtained by an Interaction Induced Coacervation

A novel method for microencapsulation of oil by coacervation is presented. The method employs segregative phase separation between sodium carboxymethyl cellulose (NaCMC) and a complex of hydroxypropylmethyl cellulose (HPMC) and sodium dodecylsulfate (SDS), which results in coacervate formation. Microstructural properties of the coacervate can be varied by tuning NaCMC-HPMC/SDS interaction, which is achieved by changing SDS concentration. Microcapsules preparation route is presented. Encapsulation efficiency and dispersion properties of microcapsules with coacervate shell of different properties and different oil content were tested. Microcapsules with smallest droplet size, the narrowest droplet size distribution, and with lowest extractability of encapsulated oil were obtained when NaCMC-HPMC/SDS interaction results in formation of the most compact coacervate shell, no matter of the encapsulated oil.

DYNAMICS OF EMULSION FORMATION

Abstract Stochastic model for oil emulsification in water has been deduced. The model in the form of differential equation was starting point to get various mathematical expressions and relations connecting different factors and parameters of the emulsification process and dispersion and Theological properties of the emulsion. Experimental investigations of particle size distribution, Theological behaviour and stability of great number of oil-in-water emulsions have been performed. The aim of the experimental investigations was to verify validity of the expressions derived. The validity of the derived expressions was checked not only for emulsions of different compositions, but also for the changes and phenomena at different stages of the emulsification process.

THE ADSORPTION OF AN ANIONIC SURFACTANT AT THE OIL WATER INTERFACE DURING EMULSION HOMOGENIZATION

ABSTRACT Adsorption of sodium dodecylbenzene sulfonate (NaDBS) on the surfaces of dispersed oil globules during homogenization of paraffin oil in water emulsions has been studied. NaDBS concentration was changed over a wide interval comprising critical micelle concentration. For the emulsions homogenized for different time intervals the total quantity and the percentage of NaDBS adsorbed, the amount and number of NaDBS molecules adsorbed per unit inter-facial area, as well as the specific surface area of dispersed phase and the area per emulsifier molecule have been determined. The amount adsorbed and density of the emulsifier layer, I.e., the area per NaDBS molecule adsorbed on the oil globule surfaces, depend not only on Initial NaDBS concentration but also, on the homogenization time and the homogenization action. This makes a difference between the adsorption behaviour under the conditions of emulsion formation and its subsequent homogenization, and the adsorption behaviour of the emulsifier at a plan...

Formation of proanthocyanidin-loaded liposomes under various conditions

The formation of phosphatidylcholine liposomes loaded with proanthocyanidins isolated from grape (Vitis vinifera L.) seeds was studied. Using scanning electron microscopy it was determined that the type and the size of the liposomes depend on various factors proanthocyanidin concentration and homogenization conditions (time and intensity). Rheological investigations of liposome dispersions show different types of flow – plastic and pseudoplastic, according to the proanthocyanidin concentration. Liposome dispersions containing 0.25–1.5% proanthocyanidin show satisfactory stability after using a temperature stress test.