Mechanical ageing of whey protein-based fouling layers by temperature-dependent gradual solidification

Abstract

Ageing of deposits arising from the processing of protein-containing fluids creates issues in cleaning that require extensive research. Differences in temperature and fouling time lead to differences in the fouling materials, while the accompanying changes in mechanical properties create challenges in predicting optimal cleaning strategies. This work analysed the strength of whey protein-based deposits by investigating the mechanical properties of homogeneous model fouling layers produced in a drying oven at defined temperatures and comparing them with thermally characterized, heterogeneous fouling layers generated in a laminar-operated flow channel. Both deposit types were analysed with a commercial texture analyser, and force-displacement curves were generated to characterize the mechanisms that lead to layer solidification. The reaction kinetics of the temperature-dependant transformation process in the fouling material was then established based on an Arrhenius approach. A height-dependent strength gradient was identified in a temperature range from 75 °C to 110 °C. The knowledge derived here regarding the limiting temperatures, as well as the identified reaction rate constants and activation energies, can help to improve the removal of fouling deposits during cleaning.