CONICET | Buscador de Institutos y Recursos Humanos

Cellulose is the most common natural plant carbohydrate. Although it is a highly hydrophilic biopolymer is not soluble in water. Solubility can be achieved altering its ordered crystalline regions by chemical substitution, generating callulose derivatives. Among them, HPMC includes a family of cellulose ethers that differ priccipally in the molecular weight, viscosity, degree of substitution and molar substitution. HPMC is used in the food industry, printing technology, and pharmaceutical applications. In the food industry, HPMC is used to improve the quality of baked products, in gluten-free breads, for innovative battered food manufacturing , low-fat edible coatings, etc. The uselfulness of ability, and the capacity to form reversible thermal gels than melt upon cooling. Surface pressure isotherms and structural and surface dilational properties of the three HPMC adsorbed films at the air-water interface were determined. The HPMC so called E4M, E50LV and F4M display different interfacial properties. In this work we present evidence that HPMC melecules were able to diffuse and saturate the air-water interface ay very low concentraions in the bulk phase. As concentration increased structural changes at the molecular level occured at the interface, wich corresponded to transitions from an expanded structure to a condensed one. When the surface concentration of HPMC was high enough, the collapse of monolayer was the observed phenomenom. The three HPMC formed cohesive films at the air-water interface that showed a strong dependence with surface pressure. Although HPMC monolayers behaved as viscoelastic, F4M and E4M generated the more elastic films and E50LV the less ones. The observed differences in interfacial properties of these films could be attributed to the structural patterns adopted by adsorbed HPMC molecules as a consequence of the distrubution of hydrophyllic and hydrophobic groups along the cellulose backbone.

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