Real-time modeling of milk coagulation using in-line near infrared spectroscopy

Abstract This paper considers the extraction of meaningful information in real-time from near infrared (NIR) reflection measurements of coagulating milk. This information can be used for developing automatic cutting time determination. NIR spectra (1000–2500 nm) recorded during coagulation were compressed by principal component analysis. Using component scores as a function of time, two models are proposed for describing the three milk coagulation processes: κ-casein proteolysis, micelle aggregation, and network formation. A model for the entire coagulation process and a composite model for the three individual coagulation processes were established and tested on 12 cheese batches. Both models fitted very well ( R 2  > 0.99) to the experimental NIR data. An algorithmic procedure is presented that is able to provide real-time parameter estimation for a semi-empirical model describing the kinetics of the milk coagulation processes as well as determining the transition times between the three different coagulation processes.