Calcium citrate insolubilization drives the fouling of falling film evaporators during the concentration of hydrochloric acid whey
Résumé
When dairy powders are produced, the mineral fraction undergoes strong modifications during the vacuumconcentration step, leading to the fouling of falling film evaporators. The objective of this study was to determinethe nature of the deposits formed during the vacuum concentration of two fouling and highly mineralizedproducts: hydrochloric acid whey and lactic acid whey. These products mainly differ in terms of their mineralcomposition: lactic acid whey contains a high level of lactic acid and traces of citrate, whereas hydrochloric acidwhey contains citrate and no lactic acid. Concentrates at different concentration factors were produced using apilot-scale falling film evaporator. The compositions of the fouling deposits as well as the precipitates present inthe concentrates were deduced from the analytical determination of the composition of the concentrates andtheir respective diffusible phases. The behavior of the mineral fraction of both acid wheys during concentrationwas shown to be very different. In the case of hydrochloric acid whey, experimental results suggested a depositionof calcium and citrate ions in the evaporator as well as their precipitation in the highly concentratedproducts. On the contrary, neither mineral deposition nor precipitation occurred during the concentration oflactic acid whey. This study underlined the key role of citrate ions in the fouling of evaporators during theconcentration of hydrochloric acid wheys.
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