Fumed silica, E551, when added to hygroscopic powder food it prevents moisture pick up and caking. It acts as a tiny spacer unit between the food particles and prevent any liquid bridge formation between the food particles. When properly dispersed with the powder it makes a monolithic coating over the powder particles.  Fumed silica being hydrophilic in nature tends to remove bound moisture from the food particles to its surface, keeps the food particles dry and acts as a barrier to absorb further moisture. It also thicken oil based food formulation, acts as an anti-settling agent, as well as carrier to convert any oil to powder such as oleo resin powders.

In spray drying process fumed silica can additionally help improve the efficiency of spray dryer, higher product recovery, drying at a lower temperature that prevents burnt black particle formation.