Optical spectral data associated with a formation fluid flowing through a downhole formation fluid sampling apparatus is obtained. Based on the obtained optical spectra data, a plurality of measures each relating the formation fluid to a corresponding one of a plurality of different fluid types are estimated. Blending coefficients each corresponding to a different one of the different fluid types are determined and utilized with the predetermined mapping matrices, each corresponding to a different one of the different fluid types, to obtain a blended mapping matrix. A parameter of the formation fluid is then predicted based on a projection of the obtained spectral data onto the blended mapping matrix.