Lidija B. Petrović

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.

Behavior of (–)-α-Bisabolol and (–)-α-Bisabololoxides A and B in Camomile Flower Extraction with Supercritical Carbon Dioxide

Abstract A systematic study of the extraction behavior of selected components of camomile flowers in extraction with supercritical carbon dioxide was carried out. (–)-α-Bisabolol and its A and B oxides, which have a wide importance in pharmacology and standardization of camomile flower products, were selected. The dependence of the yield of selected components on the pressure and/or temperature of supercritical extraction was investigated. The results obtained were correlated.

Chromatography in our investigations of camomile (Matricaria chamomilla L.)

SummaryChromatographic methods for qualitative and quantitative analysis of non-volatile and volatile compounds of camomile (Matricaria chamomilla L.) are described. For determination of flavonoids of the apigenin series HPTLC and HPLC were used. To obtain standard samples of components of camomile oil semi-preparative TLC was used. Mass spectra of these standards were obtained to provide a data base. Qualitative and quantitative analysis of camomile oil compounds by GC-MS was then possible.

Essential Oil of Chamomile Ligulate and Tubular Flowers

Abstract The essential oils of tubular flowers and ligulate flowers of two chamomile genotypes diploid (2n = 18) and tetraploid (2n = 36) were examined by GC and GC/MS. The tubular flower oils of the diploid and tetraploid genotypes were found to contain α-bisabolol oxide B (17.8% and 5.9%), α-bisabolol (34.2% and 9–6%) and α-bisabolol oxide A (24.4% and 54.3%) as major components. The ligulate flower oils of the diploid and tetraploid genotypes were found to contain α-bisabolol oxide B (13.2% and 5.6%), α-bisabolol (21.3% and 9.4%) and α-bisabolol oxide A (18.3% and 45.6%). In addition, the tubular flower oil contained (E)-anediole (4.5%) while it was not detected in the ligulate flower oil. In contrast, the ligulate flower oil contained menthone (4.4%), yet it was not detected in the tubular flower oil.

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.

An investigation of chitosan and sodium dodecyl sulfate interactions in acetic media

Polymer/surfactant association is a cooperative phenomenon where surfactant binds to the polymer in the form of aggregates, usually through electrostatic or hydrophobic forces. As already known, polyelectrolytes may interact with oppositely charged surfactants through electrostatic attraction that results in polymer/surfactant complex formation. This behavior could be desirable in wide range of application of polymer/surfactant mixtures, such as improving colloid stability, gelling, emulsification and microencapsulation. In the present study surface tension, turbidity, viscosity and electrophoretic mobility measurements were used to investigate interactions of cationic polyelectrolyte chitosan (Ch) and oppositely charged anionic surfactant, sodium dodecyl sulfate (SDS), in buffered water. Obtained results show the presence of interactions that lead to Ch/SDS complexes formation at all investigated pH and for all investigated polymer concentrations. Mechanisms of interaction, as well as characteristics of formed Ch/SDS complexes, are highly dependent on their mass ratio in the mixtures, while pH has no significant influence.

Study of interaction between chitosan and sodium lauryl ether sulfate

Chitosan is a biopolymer that has many potential applications in the industry because of its unique physicochemical properties. Many of these properties depend on its ability to interact with surfactants. The purpose of this study was to investigate interactions between chitosan (Ch), a cationic polysaccharide, and sodium lauryl ether sulfate (SLES), an anionic surfactant with ethylene oxide groups in the polar part of the molecule, in aqueous solution. Changes in the Ch/SLES mixtures were monitored by turbidity, surface tension, electrophoretic mobility, and viscosity measurements. Obtained results show that electrostatic interactions that occur at low SLES concentrations were less pronounced than hydrophobic. The region of hydrophobic interactions was linearly dependent on the concentration of the polymer, so that it ends at Ch/SLES mass ratio 1:3 by forming neutral complexes, which were completely precipitated as a coacervate phase. The research also demonstrates that small variations in structure of anionic surfactant (SDS and SLES) can lead to significant differences in interactions with cationic polymer-chitosan.

Functional properties of pumpkin (Cucurbita pepo) seed protein isolate and hydrolysate

Pumpkin seed protein isolate (PSPI) was enzymatically hydrolysed by pepsin to obtain pumpkin seed protein hydrolysate, PSPH. Investigation on solubility, interfacial and emulsifying properties of both PSPI and PSPH was conducted under different conditions of pH (3–8) and ionic strength (0–1 mol/dm 3 NaCl). PSPI had the lowest solubility, i.e. isoelectric point (pI), at pH 5. PSPH had higher solubility than PSPI over whole range of pH and ionic strengths tested. Decrease in surface and interfacial tension evidenced that both proteins adsorb at air/protein solution and oil/protein solution interface. 20 % oil in water emulsions stabilized by 1 g/100cm 3 PSPI or PSPH solution were prepared at pH 3, 5 and 8 and ionic strength of 0 and 0.5 mol/dm 3 NaCl. PSPH stabilized emulsions from coalescence at all pH and ionic strengths tested. PSPI was able to stabilize emulsions at pH 3 and 0 mol/dm 3 NaCl and at pH 8, regardless of ionic strength while emulsions at pH 5 and both 0 and 0.5 mol/dm 3 NaCl and at pH 3 when ionic strength was increased separated to oil and serum layer immediately after preparation. All emulsions were susceptible to creaming instability.

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.