Protein hydrolysates are of great interest in the food industry due to their nutritional and functional properties, but their use often implies solubilization in water and therefore hamper the use of plant proteins with inherent low water solubility. Protein solubility in water can be modified by enzymatic hydrolysis, but during this process several collateral properties of the protein hydrolysates changes. It is therefore important to determine the end-point of the process and to monitor its development. In this feasibility study, we demonstrated the potential of different spectroscopic techniques (1H NMR and IR) coupled with chemometrics analysis in monitoring the hydrolysis of five different industrial grade plant proteins by the enzyme Alcalase. Logarithmic modeling of the PCA (Principal Component Analysis) scores confirmed that they can represent a measurement of the solubilized protein material released and resulted in kinetic parameters describing the suitability of protein sources as substrates for the hydrolysis. This way, we showed that a qualitative evaluation of the degree of hydrolysis is possible using fast at-line technologies and PCA.