A multiway approach to monitoring Milk coagulation by NIR in situ

This study investigates the application of a portable near-infrared (NIR) spectrometer for real-time, in-situ monitoring of milk coagulation within a process analytical technology (PAT) framework. Coagulation trials were carried out in laboratory using raw milk and natural whey starter under controlled conditions, applying three coagulants (one calf rennet and two coagulants from Rhizomucor miehei cultures) according to a full factorial experimental design. Continuous NIR spectra (900–1700 nm) were collected through a food-grade probe and arranged in a three-way array (experiments × wavelengths × time). Multilinear partial least squares (NPLS) models were developed to relate spectral evolution to reference lactodynamograph parameters, enabling prediction of curd firming rate (k20) and curd firmness (a30). Sequential NPLS modelling further allowed assessing real-time applicability. Results demonstrate that compact NIR sensors, combined with multiway chemometrics, offer a robust and non-invasive strategy for monitoring coagulation kinetics, supporting more consistent curd-cutting decisions and improved cheesemaking control.