Adsorption kinetics and film rheology of hydroxypropylmetylcellulose at the air-water and oil-water interfaces.

CAMINO, NERINA; PÉREZ, OSCAR E; CARRERA-SÁNCHEZ, CECILIO; RODRÍGUEZ-PATINO, JUAN M; PILOSOF, ANA MR.

Córdoba

Congreso; III Congreso Internacional de Ciencia y Tecnología de Alimentos; 2009

Universidad Nacional de Córdoba. CONICET

<!-- /* Font Definitions */ @font-face {font-family:"Cambria Math"; panose-1:2 4 5 3 5 4 6 3 2 4; mso-font-charset:0; mso-generic-font-family:roman; mso-font-pitch:variable; mso-font-signature:-1610611985 1107304683 0 0 159 0;} /* Style Definitions */ p.MsoNormal, li.MsoNormal, div.MsoNormal {mso-style-unhide:no; mso-style-qformat:yes; mso-style-parent:""; margin:0cm; margin-bottom:.0001pt; mso-pagination:widow-orphan; font-size:12.0pt; font-family:"Times New Roman","serif"; mso-fareast-font-family:"Times New Roman";} .MsoChpDefault {mso-style-type:export-only; mso-default-props:yes; font-size:10.0pt; mso-ansi-font-size:10.0pt; mso-bidi-font-size:10.0pt;} @page Section1 {size:612.0pt 792.0pt; margin:70.85pt 3.0cm 70.85pt 3.0cm; mso-header-margin:36.0pt; mso-footer-margin:36.0pt; mso-paper-source:0;} div.Section1 {page:Section1;} -->    The adsorption of macromolecules at interfaces is of great interest for various industrial applications. The possibility of controlling the properties of colloidal dispersions by the use of adsorbing biopolymers requires detailed knowledge of the biopolymer structure and adsorption characteristics.    The objective of the present work was to determine the kinetics of adsorption and the film rheology of  two  hydroxypropylmethylcellulose (HPMC), called E4M and E50LV, at the air- water (A/W) and oil- water (O/W) interfaces for 10-2 % wt and 1% wt bulk concentration.      The adsorption of HPMC showed a behaviour similar to that described for proteins: (i) the diffusion from the bulk onto the interface, (ii) adsorption (penetration) and interfacial unfolding and (iii) aggregation (rearrangement) within the interfacial layer, multilayer formation and even interfacial gelation..      At the A/W interface the two HPMCs exhibited different behaviour than at the O/W interface. The adsorption rate (Kads) of HPMCs at the O/W interface increased with bulk concentration whereas Kads at the A/W interface decreased with bulk concentration. The effect of air phase on the structure adopted by the polysaccharide at the interface was  different.     The penetration, unfolding and rearrangement of these polysaccharides at both interfaces control the rate of adsorption. The rate of rearrangement at the A/W interface resulted slightly lower than at the O/W interface. A greater unfolding of the HPMCs would occur at the O/W interface due to solvation by the oil of the hydrophobic side chain. For E50LV  10-2% wt bulk concentration, the rearrengement step at the O/W interface resulted the highest. This could be due to the absence of a steric impediment since E50LV posses the lowest molecular weight and higher amount of CH3 groups with less molecular restrictions for adsorption at this interface.     At O/W interface both HPMCs films increased the solid character (Ed) with time but slower than at the  A/W interface. However, the final Ed values were  similar.      For systems containig 1× 10-2% wt bulk concentration, a more viscoelastic character was observed for the films formed at the A/W interface. At 1% wt bulk concentration, both HPMCs showed more viscoelastic behaviour than at  1× 10-2% wt bulk concentration at both interfaces.      The knowledge of surface behaviour of HPMCs at the A/W and O/W interface, can be useful when studying emulsion and foam formation and stability.