Role of amorphous lactose in the caking of (alpha)-lactose monohydrate powders

The amorphous content has a significant effect on the moisture sorption and caking characteristics of α-lactose monohydrate powder. The sticky liquefied amorphous lactose consolidates the lactose particles forming lumps. In a caking study on α-lactose monohydrate powder mixed with amorphous lactose compacted in little paper cylinders to model the bulk powder in paper bags, severe caking occurred in α-lactose monohydrate powder containing more than 10% amorphous lactose. The hardness of the caked lactose did not markedly increase when stored at 57% and 75% relative humidities (at 25ÂÃ"šÃ‚°C for 3 months). However, if the starting material initially contained more than 50% amorphous lactose, the hardness of the cakes increased.