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ABSTRACT
The major cause of fouling of processing equipment in the Dairy Industry used for the pasteurization of milk and whey resides in particle formation in the bulk of the dairy fluid. As a result of processing at elevated temperatures, the heat sensitive whey proteins aggregate and calcium phosphate becomes insoluble and precipitates. Hence, the process of fouling can be understood as a subsequent deposition of these particles onto the heating surface.
On the basis of model calculations it is demonstrated that at neutral pH both the calcium phosphate particles, and to a limited extent also the whey proteins, are attracted by stainless steel. This is the result of the monopolar character of steel, which leads in an aqueous environment to an attractive Lewis acid/base interaction term with both components. In combination with the Lifshitz-van der Waals contribution both contributions to the overall interaction are sufficiently large to overcome the electrostatic repulsion at the given pH.
This result points to the specific role of stainless steel in the process of fouling and has far reaching consequences for the way the process of fouling can be controlled as the behaviour of the contaminants, e.g. their heat sensitivity, can not be altered.