Influence of nitrogen gas injection and agglomeration during spray drying on the physical and bulk handling properties of milk protein concentrate powders

This study investigated the influence of injecting nitrogen (N₂) gas under high pressure into milk protein concentrate (80%, w/w, protein; MPC) prior to spray drying and examining the physical and bulk handling properties of regular (non-agglomerated) and agglomerated powders. MPC powders produced using the N₂ injection (NI) process had significantly lower bulk density and flowability, higher wall friction angles and increased levels of interstitial and occluded air. Agglomerated MPC powders had higher flow index values, lower wall friction angles, but were more friable, compared to regular powders. Surface composition analysis of MPC powders showed that NI caused fat to preferentially migrate to the surface in comparison to powders spray dried without NI. The results obtained in this study demonstrate that the injection of N₂ into liquid MPC directly prior to spray drying, as well as agglomeration by fines return, can produce ingredients with unique particle and bulk powder properties.