This study compared the UHT (145 degrees C for 5 s) stability and fouling behavior of high protein milk dispersions prepared from reconstituted low heat skimmed milk powder (RSMP) and milk protein concentrate powder (RMPC). It was found that RMPC at 10 and 14% protein content was more UHT stable as compared to lower protein content RSMP (3.25, 6.5, 7, 7.5, 8%). Matching the total solids and mineral composition of 7.5-RMPC with 7.5-RSMP by addition of minerals and lactose markedly reduced its UHT stability (UHT run-time reduced to 66 min from > 120 min). The RP-HPLC analysis showed increased casein dissociation but similar whey protein aggregation in 7.5-RSMP as compared to 14-RMPC. UHT processing lead to formation of larger particles in case of 7.5-RSMP (1.84 mu m D(0.9)) as compared to 14-RMPC (0.23 mu m D(0.9)). It was observed that mineral environment affected protein interactions leading to the differences in UHT behavior of RSMP and RMPC.