Maltodextrin was analyzed as a model compound representative of polysaccharides. A relatively smooth surface was obtained by pressing the maltodextrin powder in a small trough. The C 1speak component was split into three components with the same FWHM. The main component was found at 286.3 eV and was attributed to carbon involved in the alcohol functions. The component found at 287.8 eV was attributed to carbon in the acetal function; the alcohol to acetal ratio([C_—OH]/[O—C_—O])was 0.21, i.e., close to the stoichiometric ratio 0.20. A component found at 284.8 eV indicated the presence of hydrocarbon-like surface contamination. The O 1speak showed only one component at 532.7 eV; oxygen involved in hydroxyl could not be distinguished from oxygen involved in a acetal function. The surface analysis of model compounds was performed under conditions of practical significance for the analysis of microbial cells and of materials treated by biological fluids. This approach allowed quantification of chemical functions of biosurfaces and modeling of the composition of the latter in terms of classes of biochemical compounds (polysaccharides, proteins, lipids, …)