Milk is one of the most important dietary products which contains nearly all the nutrients necessary to sustain life [1]. Being a complex natural fluid in which water is a major constituent, milk contains varying quantities of lipids, proteins and carbohydrates as well as smaller amounts of minerals and other fat-soluble or water-soluble components [2].
A number of analytical methods have been developed to determine the chemical composition of milk, providing a detailed analysis of fat, protein, carbohydrates and dry matter which is required for quality control purposes and consumer information. The traditional methods used for milk, i.e. Röse-Gottlieb for fat determination, Kjeldahl for proteins and polarimetry or gravimetry for lactose quantification, have been replaced by modern techniques that could significantly reduce cost and time needed for milk analysis [3] and [4]. Considering the global production scale of milk and milk-derived products, simplification of analytical procedures would be extremely advantageous. Fifty years ago, infrared (IR) spectroscopy was found to be a valuable technique allowing for fast and accurate determination of the chemical composition of milk and several IR techniques utilising both mid- (MIR) and near infrared (NIR) spectral ranges were used [5], [6], [7], [8] and [9]. Infrared spectroscopy was adopted for use in commercially-available milk analysers and has become a standard tool for the quantification of milk components [3] and [5].