A Comparison of Milk and Whey Fouling in a Pilot Scale Plate Heat Exchanger: Implications for Modelling and Mechanistic Studies

The fouling from whey protein concentrate (WPC) and milk in a plate heat exchanger have been compared. Significant differences are seen: in the pasteurizer and UHT section, heavy fouling is seen for both fluids, but although fouling from WPC in the intermediate sections is extensive, no fouling from milk occurs. The morphology of deposits has been studied using SEM, and Elemental Mapping. Compositional analysis of the surface deposits was also examined. The morphology studies showed that for both fluids, fouling in the pasteurization section of PHE was mostly aggregated protein. For milk, as the processing temperature increased, the deposit changed to become mineral-based, however, the WPC continued to show protein fouling right up to UHT temperatures. The data suggests that it may be difficult to extrapolate fouling models from WPC to milk fouling in the high-temperature region. Bulk aggregation reaction and mineral fouling at UHT temperatures have been identified as mechanisms which influence the fouling process and need further investigation.