Laboratory methods to predict the cleaning behaviour of egg yolk layers in a flow channel

Cleaning-in-place (CIP) is an established technique for the cleaning of industrial food processing plants. To design CIP protocols, laboratory methods are helpful to predict the cleaning behaviour and to reduce the number of costly in situ cleaning investigations. In this work, laboratory methods (differential scanning calorimetry, rheology, optical swelling measurements and micromanipulation) were used to analyse different aspects and stages of the cleaning process (swelling, chemical and mechanical actions, phase transition and mass transfer). The suitability of these methods to predict the cleaning behaviour was tested by using a representative egg yolk deposit. Temperature (24-60 °C) and NaOH concentration (0-1.5%) of the cleaning fluid served as independent factors, and the time necessary to remove the deposit in a flow channel was evaluated using an optical method. Cleaning time decreased with increasing temperature and also depended on NaOH concentration. Within the examined limits, the pushing energy measured by the micromanipulation method showed the best correlation with cleaning time, whereas swelling, diffusion and rheological measurements only reflected tendencies of the cleaning behaviour.