Lactose mother liquor stream valorisation using electrodialysis

Abstract

To increase lactose yield, crystallisation of lactose from lactose mother liquor (LML; a by-product containing high amounts of lactose, proteins and minerals) can be applied, but inorganic ions and organic acids inhibit crystallisation and so reduce final product yield. Electrodialysis is proposed for desalting LML before crystallisation to increase lactose yield. Basic parameters of the electrodialysis process for removal of inorganic ions and organic acids as well as changes in membrane properties during electrodialysis are presented. Electrodialysis provided high removal of inorganic ions coming from LML (64 ± 5%), while lactose content did not decrease (11.7 ± 0.2 g L−1 in desalted LML). Furthermore, titratable acidity decreased 2-fold (from 25 ± 2 to 13 ± 2 °SH), thus ensuring more efficient crystallisation process of lactose from desalted LML, when coupled with electrodialysis. The cation-exchange membranes after ED showed increased specific resistivity and permselectivity, while the opposite effect was observed for the anion-exchange membranes.