a1 Government Dairy Research Station, 9230 Melle, Belgium
a2 Biometric Unit, Agricultural Research Centre, 9220 Ghent, Belgium
The influence of preheating intensity was examined on deposit formation in an indirect ultra high temperature (UHT) plate heat exchanger and on some quality parameters of the UHT treated milk, such as taste, proteinase inactivation and protein destabilization during storage. Response surface methods were used to define the relationship between the forewarming conditions and the responses. More intense forewarming reduced the fouling rate in the UHT plate section, resulting in longer operation times. While a greater inactivation of the proteinase(s) in the milk was obtained, the taste of the UHT milk was adversely affected, as well as the physical stability during storage owing to higher sedimentation. An optimum temperature/time range for the preheating process could be defined within the temperature/time range of 76–80 °C/40–70 s at which adverse effects were minimal, and positive effects were maximized.
(Received December 14 1987)
(Accepted April 27 1988)