Changes in physical and biochemical properties of spray dried camel and bovine milk powders

This study aimed at investigating the changes in skim camel milk (SCMP) and skim bovine milk (SBMP) powders produced by spray-drying. The physical (sorption isotherms at 25 degrees C and the glass transition temperature T-g at 0.13, 0.23 and 0.33 of water activities (a(w))) and the biochemical (LC-MS, before and after drying) properties were assessed. Compared to SBMP, the results for SCMP indicated lower protein denaturation extent, lower critical a(w) for lactose crystallization (a(w) = 0.60 instead of 0.70), and lower T-g at 0.13 of a w (54.6 +/- 1.4 degrees C instead of 57.8 +/- 0.4 degrees C). Fitted to Guggenheim, Anderson and De Boer (GAB) model, the water sorption isotherms showed that both powders exhibited the same monolayer moisture content (X-m = 2.0 g 100 g(-1), p > 0.05). These findings were linked to the absence of beta-lactoglobulin, the high surface lactose content, the high initial lactose crystallization and the low size distribution (d(50) < 10 mu m) of SCMP.