The optimal functioning of a pasteurizer is achieved when the product receives the correct level of pasteurization without excessive consumption of water or energy and with the appropriate use of water treatment, cleaning and disinfecting agents, etc. This can only be attained if the chemical properties and physical movements of the water in the pasteurizer are properly understood. Chemical tracers have long been used to study water systems both in nature (e.g. the use of fluorescein to locate an underground stream connecting two apparently separate rivers) and in industry, but for various reasons none of the substances traditionally used for the purpose can be considered suitable for use in pasteurizers. However, a new tracer product based on a chemically inert fluorescent compound, developed by the Nalco Chemical Company and marketed under the name of "Diagnostic TRASAR", has become available and is shown to be suitable for pasteurizer applications by the case history of its use in a US brewery. In the case described, several pasteurizers were connected to a single recirculating water system. The tracer was successfully used to determine the system volume (by adding it at one point, waiting for its distribution through the system to reach equilibrium and calculating the system volume from its equilibrium concentration and the quantity originally added) and the "holding time index" (the time taken for half the originally added quantity of tracer to be lost from the system) from which other important system parameters were calculated, enabling the efficiency of water, energy and disinfectant utilization to be substantially improved with consequent economic, environmental and hygienic benefits.
Keywords : disinfection efficiency energy flow fluorescence measurement pasteurisation pasteuriser staining water