Fatty food foams are in fact foamed emulsions. The state of fat (occurring either liquid or in various amounts of polymorph forms depending on temperature/time) largely contributes to their structural and textural properties. The characterization of a foam based on lard is presented. The evolution of the fat's physical state as a function of temperature was followed by X-ray diffraction coupled with differential scanning calorimetry, DSC and NMR relaxometry. The mechanical properties of each sample were followed in dynamic mode. The fat's physical state has a direct effect on the mechanical properties of the crude and cooked foams. For the emulsion and then for the corresponding foam, the contribution of fat to the rigidity of the system depends on its degree of dispersion. The structure and the properties of the foam are clearly dependent on the stability of the emulsion while heating. This evolution can be evidenced by following the rheological properties in temperature cycle up to 50°C.