Effects of the addition of various minerals, proteins and salts of organic acids on the principal steps of α-lactose monohydrate crystallisation

To study the effects of whey constituents on lactose crystallisation, a model based on population balance and taking into account mutarotation was implemented. Outputs were the nucleation constants (B0, kn0) and the growth rate constants (kg0, g0). Batch crystallisation of a lactose solution (70 g 100 g 1 water) was studied with and without addition of various organic acids, salts, galactose and proteins. Kinetics and crystal size distributions were monitored using refractometry and laser light scattering. Factorial analysis of the results highlighted that the presence of organic acids (lactate, citrate) leads to faster crystallisation and confirmed the fact that whey proteins are slowing down the crystal growth step. The results of this study make a contribution towards a better understanding of lactose crystallisation.