Effect of milling on the caking behaviour of lactose

Milling (i.e. hammer, rotary speed, ring and jet) lactose powder altered its particle size and size distribution. The milling process might also cause the formation of amorphous lactose and increase the free moisture content of the powder. Conditioning the milled lactose powder, which contained predominantly α-lactose monohydrate and less than 10% amorphous lactose, to a relative humidity as high as 75% (at 25°C for up to 3 months) did not completely eliminate the amorphous lactose.