The phase separation kinetics have been studied with Small angle light scattering (SALS) in strongly asymmetric aqueous mixtures of gelatin and dextran, above and below the gelation temperture of gelatin. The focus is on solutions with gelatin as the majority component. The phase separation gives rise to a distribution of dextran-rich spheres in a gelatin-rich matrix. The SALS pattern shows a maximum, which was interpreted as being due to the interplay between the scattering from dextran-rich nuclei and a surrounding layer depleted in dextran (depletion layer). The size and concentration of the spherical nuclei and their depletion layers were followed in time at temperatures above and below the gelation temperature of the matrix. The results show a strong and complex dependence on temperature and total polymer concentration of the separation kinetics.