Effect of galacto-oligosaccharide concentration on the kinetics of lactose crystallisation

Abstract Galacto-oligosaccharides (GOS) are said to have a retarding effect on the nucleation and growth of α-lactose monohydrate crystallisation. Studies regarding the kinetic parameters for crystal growth and nucleation were conducted utilising gravimetric analysis and laser light scattering to follow the lactose crystallisation. A statistically significant retarding effect of GOS on lactose crystal growth at concentrations between 0.8 and 3% (w/w) GOS of total solution was observed. A significant nucleation suppressing effect was confirmed further. Studies concerning the change in crystal morphology revealed that as GOS concentration was increased, a transition from the common tomahawk shape to a shape with shortened crystal faces away from the apex to a needle like appearance occurred, strongly suggesting a growth retardation effect on the (010) face. Crystals subjected to high pressure liquid chromatography (HPLC) analysis did confirm an incorporation or inclusion of GOS into the crystal lattice.