Characterisation of gelatin/surfactant interaction and its relevance to liquid film coating.

Publisher Summary This chapter describes the main physico-chemical properties of gelatin solutions and gelatin/surfactant mixtures, that is, the principles of their interaction, the influence of surfactants on the secondary structure of gelatin in the bulk phase and at the interface, the modification of the interfacial tension, the adsorption layer thickness, and the changes of the rheological properties in bulk and interfaces. The strength of interaction between gelatin and surfactant depends on the charge and the hydrophilic/lipophilic balance of the surfactant. It is strong for anionics, weaker for cationics, and very weak for non-ionics. As a consequence of the interaction, the secondary structure of the gelatin is changed starting from a certain surfactant concentration. At high surfactant concentration the triple helical structure is changed into a β-sheet structure. In contrast, the adsorption of triple helical structured complexes is favored and a considerable amount of triple helix structures is found at the interface. Gelatin/surfactant complexes in a wide range of surfactant concentration govern the surface behavior.