Milk fouling is the main cause of progressive decline in the rate of heat transfer in a UHT milk sterilizer, which results in a drop in milk outlet temperature as the processing advances. Increasing steam temperature is one of the ways to overcome the drop in milk outlet temperature and prolong the operating time before the processing is stopped for cleaning of deposits in the heat exchanger. A computer model is developed for accurate control of milk temperature as affected by fouling. It can calculate accurately the increase in steam temperature required for maintaining the desired milk sterilization temperature. The results with steam control are compared with the results without any control and this procedure was found satisfactory for controlling the milk outlet temperature. The procedure described can be applied to any heat exchanger with minor modifications, if necessary. (c) 2004 Elsevier Ltd. All rights reserved.