Controlling the properties of lactose particles extracted in ternary and quaternary systems

In a sophisticated technique referred to as extractive crystallisation, a second miscible volatile solvent such as alcohol is added to the binary system lactose-water to reduce the solubility of lactose and hence 'push' the crystals out of the aqueous solution. Our research suggests that using ethanol as the second solvent can produce needle-shaped crystals having the lowest median size of 8 m, and b-lactose content up to 60% at 60 C. On the other hand, using two immiscible solvents, one non-volatile and one volatile, such as by adding ethanol to the ternary system, lactose-water-glycerol, can make large needle or plate crystals with b-lactose content up to 90% at 70 C. This work also generates for the first time the triangle diagram comparing the solubility of lactose in the glycerol and ethanol aqueous solutions at equilibrium and at different temperatures.