Abstract: A method of quantitative measurement of fat in a liquid sample by an infrared attenuated technique is disclosed. The fat is present in the form of an emulsion of particles causing Christiansen's effect, i.e. the combined effect of light-scattering and anomalous dispersion. The method comprises transmitting infrared radiation through the sample, determining the infrared absorption of the sample in at least one measurement waveband exhibiting the Christiansen's effect, and with reference to a reference waveband. The wavebands are selected such that the fat determination is essentially independent of the Christiansen's effect. The wavebands are preferably selected such that the fat absorbance, i.e.