Quantitative Analysis of Milk and other Emulsions by Infra-Red Absorption

Abstract

A BEAM of radiation passing through an emulsion can be attenuated by both absorption and scattering effects. Quantitative absorption measurements on such systems are only reliable when the effects of scattering are made small in comparison with those of absorption ; that is, when the ratio of the refractive indices of the two phases approaches unity and when the size of particle is considerably less than the wave-length. For milk, the ratio of the fat/serum refractive indices is approximately 1.1 and since the mean fat globule diameter of homogenized milk samples is about 1µ, scattering effects will be expected to be small at wave-lengths greater than 5µ. Homogenization will therefore reduce photometric errors caused by variations in the sizes of fat globules of milk samples from cows of different breeds and in different states of lactation.