Extensive lactosylation of milk proteins in standard skim milk powder dried against air between 185 and 90 o C (inlet and outlet temperatures of the air) was detected by capillary electrophoresis. Optimisation of the drying conditions included keeping the outlet temperature low (preferably <80 o C), since this was the parameter which most affected the extent of lactosylation of milk proteins. The inlet temperature was set in order to obtain the best compromise between a low extent of lactosylation and a high drying rate (170-175 o C). These conditions allowed the manufacture of low-lactosylated skim milk powder. Storage of freeze-dried and control low-lactosylated skim milk powder at different temperatures showed that both temperature and moisture content affected the progress of lactosylation during storage. Further drying to less than 2.5% moisture content (w/w) and storage at low temperatures were required to prevent the development of lactosylation in the low-lactosylated skim milk powder.