Valorization of side-streams from lactose-free milk production by electrodialysis

Lactose-free milk production generates large volumes of a by-product, rich in lactose, known as nanofiltration retentate (NFR). However, enhancing the value of this by-product is challenging due to the presence of high concentration of minerals which are believed to induce a salty and bitter taste. To overcome this issue, the present project aims to study the feasibility of an electrodialysis (ED) process for demineralization of NFR. In addition to native NFR, two subsequent dilutions of NFR were tested reducing the electric conductivity from 5.5 ± 0.2 to 4.7 ± 0.3 and 3.7 ± 0.1 mS·cm⁻¹ while three voltages of 5, 10 and 15 V during ED were applied. The ED efficiency was measured in terms of demineralization rate, mineral removal kinetics, system resistance and energy consumption during the process. A demineralization level higher than 90% was reached within 120 min without significant loss of lactose. But, total nitrogen content was lost to some extent. The demineralization rate and energy consumption increased with the applied potential, where the demineralization efficiency declined significantly after 80% for all processing conditions. A predictive model was therefore developed to estimate the time required for 80% of demineralization as a function of initial conductivity and voltage applied.