Formation of cold-set gels from mixtures of the bacterial polysaccharide gellan and the modified potato starch Paselli SA2 has been studied by mechanical spectroscopy, turbidity measurements, and confocal and transmission electron microscopy. The hot solutions gave no indication of a tendency to liquid-liquid demix over normal concentration ranges. A microphase-separated gel structure arose after a substantial period at 4 degrees C, but electron microscope evidence suggested aggregation of the starch polymers in a fine-pored homogeneous preformed gellan network, not simple separation of the two components into distinct gel phases. A novel method based on assessing local effective polymer concentrations during gelling, from mechanical cure curves and turbidity data, also suggested that a simple phase-separated microstructure was inappropriate, and an interpenetrating network model was able to describe shear modulus-composition data for the final gels.