THE EFFECT OF PARTICLE SLIP ON THE STERILIZATION OF SOLID-LIQUID FOODMIXTURES

A number of food processes involve heat transfer to solid-liquid mixtu res. Continuous sterilisation plants consist of three sections: heatin g, holding and cooling. The system brings a flowing mixture to a suita ble temperature, and keeps it at this temperature long enough to ensur e the required sterility. Overprediction of the steriliser component s izes can result in excessive nutrient degradation and quality loss of the product. Experiments have demonstrated that particles and liquids can move at different velocities in real food systems. A one-dimension al computational model, which explicitly takes account of the variatio n in velocities, has been developed. The model has been used to study the variation in design length which results from solid-liquid slip. S teriliser sizes have been calculated for varying solid-liquid slip vel ocities and delivered solids concentration for a fixed flow rate. Plot s of the variation of heat tube length as a function of slip velocity and solids concentration are presented as a function of particle Blot number, and the possible effects on the design of real systems suggest ed.