Fluorescence spectroscopy investigation of acid-or rennet-induced coagulation of milk

Milk coagulation is the primary step in the development of texture of most dairy products. However, there is a lack of techniques to study network structure at a molecular level. Front-face fluorescence spectroscopy has been used to investigate structure evolution, at a molecular level, during milk coagulation. We studied three different coagulation processes, which are known to generate gels exhibiting different textures and structures. Emission fluorescence spectra of the protein tryptophanyl residues were recorded for each system during the milk coagulation kinetics. Principal component analysis was applied to the collection of normalized fluorescence spectral data of the three systems to optimize their descriptions. The results showed that front-face fluorescence allows detection of structural changes in casein micelles during coagulation and discrimination of different dynamics of the three coagulation systems. The rapid and noninvasive method developed in this study allowed the investigation of network structure and molecular interactions during milk coagulation.