Sandra Bučko

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.