ABSTRACT
Greek Letters ............................................................................................ 626 Subscripts ................................................................................................. 627 Superscripts .............................................................................................. 627
Appendix A: Plug-Flow Thermal Model of the PHE .......................................... 627 References ............................................................................................................. 629
Thermal processing of liquid foods targets the inactivation of pathogenic and spoilage microorganisms or undesired enzymes that compromise food safety and product shelf life. Process conditions must be carefully selected so that the desired level of sterility is achieved with minimal deterioration of nutritional and sensory quality. Plate heat exchangers (PHEs) are widely employed for continuousflow thermal processing of low-viscosity liquid foods such as milk, cream, fruit and vegetable juices, liquid egg, or beer. The main advantages of PHEs are design and operational flexibilities, high thermal effectiveness, naturally induced turbulence, good fluid and temperature distributions, and ease of sanitation. Nevertheless, processing of high-viscosity fluids or fluids with particulate matter is not recommended since the small flow space between plates can lead to high pressure or even obstruction (Lewis and Heppell, 2002; Kakaç and Liu, 2002).
