INVESTIGADORES
PEREZ Oscar Edgardo
congresos y reuniones científicas
Título:
Hydroxypropylmethylcellulose at the air-water interface: dynamic of adsorption and films rheology
Autor/es:
PÉREZ, OSCAR E; CARRERA-SÁNCHEZ, CECILIO; PÉREZ, OSCAR E; PILOSOF, ANA MR.
Lugar:
Montevideo, Urugüay
Reunión:
Congreso; XIII Seminario Latinoamericano y del Caribe de Ciencia y Tecnología de Alimentos; 2004
Institución organizadora:
Universidad de la República
Resumen:
Hidroxypropylmethylcellulose
(HPMC), a water soluble polymer used in food, ceramic processing, cosmetics and
pharmaceutical for drug-delivery systems, is able to adsorb at interfaces and
stabilize foams and emulsions.
The objective of the present
work was to characterize the behaviour of three different commercial HPMC at
the interface from a kinetic and rheological point of view.
The HPMCs studied were E4M,
E50LV and F4M from Methocel Dew Chem-Colorcon SA. The concentration of HPMC
varied between 10-4 and 1% w/w. Temperature, pH and ionic strength
were maintained constant at 20ºC,
7 and 0.05 M
respectively. The dynamic of adsorption and the rheological parameters, the
viscoelastic modulus (E) with its elastic (Ed) and viscous component (Ev) and
the relative viscoelasticity (tan d) of the films
were determined in an automatic drop tensiometer.
E4M diffused an order of
magnitude faster than the other types of HPMCs. E4M could have a more
appropriate chemical structure to get the interface in short periods of time in
spite of being more viscous. Differences between the three gums were also found
in the unfold and rearrangement rates.
E4M and F4M showed a
transition from a more expanded structure (Structure I) to a more condensed
structure (Structure II) at a surface pressure of 20 mN/m, and collapsed at
29.4 and 27 mN/m. However, E50LV did not show such structural transitions and
collapsed at 32 mN/m. The evolution of the elastic component of the modulus
over adsorption time was related to the structural changes of HPMC.
At the pseudo-equilibrium
E50LV films showed the less solid character, and E4M showed de highest.
It could be concluded that
HPMCs films showed different interfacial characteristics depending on the
structure acquired at interface which is related to the molecular characteristics.