The influence of film-forming techniques on the moisture barrier efficiency of acetylated MG (AMG) films tested in real conditions at the interface between an agar gel (AG) and sponge cake (SC) was investigated. Three systems were studied: self-supporting films, sprayed films, and cast films. The moisture distribution profiles of the AG/AMG/SC systems were determined experimentally and by using a predictive model for both selfsupporting films of various thicknesses and formed-in-place (sprayed or cast) films. Increasing the thickness of the self-supporting films had no influence on moisture barrier efficiency, probably due to the high stability of the AMG material. Formedin-place films were 40% less efficient than the self-supporting films whatever the application procedure used (spraying or casting) because of their poor integrity due to the roughness of the SC surface.Edible lipid films have been widely used for their important moisture barrier properties (1,2). A variety of lipid compounds, including acetylated MG (AMG), natural waxes, and surfactants, have been used as protective coatings to block moisture transfer between compartments of a composite food (3-5). These lipid films were found to be efficient in delaying the moistening of a "dry" compartment in contact with a "wet" compartment but only in the restrictive conditions encountered in laboratories, where films were deposited on a smooth surface to form self-supporting layers. In commercial situations, formed-in-place films produced by spraying appear to be the best means of applying a fatty layer on a food surface. However, the moisture barrier performance of these films has received little attention. The moisture barrier properties of lipid layers have most often been characterized by permeability measurements on freestanding films; consequently, they cannot be easily realized on formed-in-place films in direct contact with food. Moreover, permeability characterizes film barrier performance in the restrictive conditions of film thickness, temperature and humidity (6-8). In most cases, this value cannot be extended to different sets of conditions and film thicknesses (9).The barrier performance of lipid-based films is sensitive to parameters such as their chemical group, aliphatic chain length, the presence of unsaturation, and polymorphism. The chemical group influences moisture barrier efficiency through the hydrophobicity of the molecules that interact more or less with water. For example, hydroxyl groups have less affinity for water than carbonyl and carboxyl groups. For groups having the same chemical nature, carbon chain length modifies the barrier properties, usually with a decrease in permeability with an increase in carbon number (from 14 to 18) (10). When the degree of unsaturation increases, the m.p. of the lipid decreases, and as a consequence, so does the barrier efficiency. Polymorphism also strongly influences barrier performance: Kester and Fennema (11) found that crystallization in the β form increased the moisture transfer resistan...