isomerisation rate was slow and only ca. 3% conversion (0.12–0.13 g lactulose/100 ml) was detected in MCP after 150 min, and in control lactose solution after 120 min. In the presence of catalyst a significantly higher level of conversion was achieved in both solutions and at earlier stages of heating, i.e. the maximum conversion detected was 13.5% in control but only 6.2% in MCP after 60 min.