Structural changes of milk proteins during heating of concentrated skim milk determined using FTIR

This work aimed to establish the impact of total solids (TS) concentration (9, 17 and 25%) of raw skim milk on the conformational properties of proteins during heating up to 121 °C. Conformational changes were determined using Fourier transform infrared spectroscopy and correlated to physicochemical properties of the system. The results showed high total solids dependence in rearrangement of β-sheet of β-lactoglobulin. Heat denaturation of whey proteins was concentration and temperature dependant. The micelle appeared to undergo temperature dependant dissociation that induced redistribution of helical and loop structures. The conformational changes were further evaluated with principal component analysis and normalising for a concentration effect for all samples. The most affected structures were located in the region 1620–1655 cm⁻¹ including intra- and inter-molecular β-sheets, α-helix/loop structures and randomly distributed structures. These findings may assist in predicting the heat stability of concentrates.