FOULING OF HEAT-EXCHANGERS IN THE DAIRY-INDUSTRY

A general overview is given of the main factors in the fouling of proc essing equipment used for heating dairy fluids. The data collected ind icate that the primary step in fouling is the adsorption of a monolaye r of proteins onto the wall of the heating equipment at room temperatu re. Real fouling (i.e., the formation of macroscopic layers of foulant s), however, is caused by particle formation in the bulk of the liquid being processed. These particles include both whey protein aggregates and calcium phosphate particles. Their formation is heat induced, and the deposition takes place through diffusion toward the heating surfa ce. Only very high flow rates are able to prevent their deposition and subsequent sticking. To better control the process of fouling, specia l attention is given to the parameters affecting the formation of both types of particles and how their formation can be retarded or prohibi ted, including the role of calcium sequestrants, pH, preheating, and f low rate herewith. (C) Elsevier Science Inc., 1997.