Whey protein gel - mechanical cleaning capability through modelling and experimental testing including compression and wire cutting investigation

Abstract Whey protein has been used extensively to investigate the efficiency of procedures for cleaning dairy production equipment owing to the chemical reaction it undergoes at high temperature, similar to the formation of fouling deposits during heat treatment. In addition to the chemical and thermal aspects, a detailed understanding of the fundamental mechanical and fracture mechanisms that significantly influence the success of the cleaning procedure is indispensable. Consequently, to determine the basis for the mechanical detachment of whey protein isolate, in the present study, the mechanical characteristics and fracture properties of whey protein gels (WPGs) with a protein content of 15% and a treatment temperature of 80 °C were determined. For purely mechanical characterisation, axial compression and compression relaxation experiments were performed. The results suggest a non-linear stress–stretch behaviour combined with time-dependent mechanical characteristics. To characterise the fracture properties of WPGs, wire cutting experiments were performed. Based on a viscoelastic numerical model and the corresponding parameters identified from the experimental investigations, the cutting procedure of WPGs was simulated by assigning a fracture criterion, and the critical stress was determined based on the measured cutting forces.