Lactosylation of milk proteins during the manufacture and storage of skim milk powders

Extensive lactosylation of milk proteins in standard skim milk powder dried against air between 185 and 90 degreesC (inlet and outlet temperatures of the air) was detected by capillary electrophoresis. Optimisation of the dry ing conditions included keeping the outlet temperature low (preferably < 80 <degrees>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 degreesC). These conditions allowed the manufacture o f low-lactosylated skim milk powder. Storage of freeze-dried and control lo w-lactosylated skim milk powder at different temperatures showed that both temperature and moisture content affected the progress of lactosylation dur ing storage. Further drying to less than 2.5% moisture content (w/w) and st orage at low temperatures were required to prevent the development of lacto sylation in the low-lactosylated skim milk powder. (C) 2001 Elsevier Scienc e Ltd. All rights reserved.