Plant and Equipment: Pasteurizers, Design and Operation

Pasteurization of milk is one of the most important public health interventions applied in the food industry, and renders raw milk safe for consumption or dairy product manufacture, once combined with effective hygienic packaging and refrigerated storage; the process also extends the shelf life of milk, adding convenience to a naturally highly perishable product. In modern large-scale industrial processing, pasteurization is performed by heating milk to 72-74. °C for 15-30. s using plate heat exchangers, followed by rapid cooling, and is often integrated in a single process line with other unit operations such as homogenization or fat separation; a modern pasteurizer is both highly efficient (due to extensive recovery of energy) and fitted with numerous safeguards to ensure product safety. In addition, rapid assays for surrogate enzymes to confirm the application of correct heating conditions are widely used and validated. While such processing has been applied for decades, the heating conditions used may occasionally be revised on the basis of increased understanding of the heat resistance of emerging pathogens. This article discusses the operation of modern milk pasteurization plants and the scientific background to the conditions most commonly used.