Fouling behavior of coconut milk at pasteurization temperatures

Fouling by coconut milk at different heating temperatures (50–54.5 °C, 60–64.5 °C, and 70–74.5 °C) and at three volumetric flows (2,4 and 6 LPM) in a test section equipped with four flat plates was studied. Measurement of the overall heat transfer coefficient (U) and the compositions of deposit mass were completed in order to obtain fouling factors (Rf) and an empirical model for the rate of increase of Biot number (∆Bi/∆t) as a function of the temperature (T) and the flow (F). The results illustrated that the fouling factor increased, when the temperature fell due to a combination of chemical reaction fouling from proteins and precipitation fouling from fat. The fouling factor also increased, when the flow was lowered due to a slow rate of deposit removal introduced by small shear force. Combination of the two effects revealed that the effect of flow was less significant at higher temperatures. All results can be confirmed by an analysis of fouling compositions. At high temperature conditions, more denaturation of proteins resulted in less ability to entrap fat globules onto heating surface. The heat resistance was found decreasing with increasing temperature.