Direct measurement of the cohesive strength of whey protein gel in contact with NaOH by wire cutting experiments

Abstract

For the design of cleaning processes in general and for the parameterization of process models in particular, it is necessary to determine cleaning-relevant material properties of the soils and their change depending on cleaning fluid and soaking time. The dominant cleaning mechanism depends on the balance of cohesive strength within the soil and the adhesive strength to the substrate. This paper describes a method for the direct measurement of the cohesive strength of heat-induced whey protein gel (WPG) in virgin state and after interaction with sodium hydroxide. The forces required to separate the WPG with a wire in different soil layer positions are determined by varying the wire diameter. By approximating the cutting force as a function of the wire diameter, interactions between the wire and the WPG on the cutting force can be compensated to determine the cohesive strength. The method developed deals with the control of the wire preload based on the acoustic measurement of the first natural frequency of the vibrating wire. To define the cutting position of the wire within the gel, the phase boundary between soil and cleaning fluid was optically determined.