Partial demineralization and concentration of acid whey by nanofiltration combined with diafiltration

In this paper, nanofiltration (NF) combined with continuous variable volume diafiltration (CVVD) of cottage cheese whey (also known as acid whey) was investigated to simultaneously concentrate and partially demineralize it. The experiments were carried out in a laboratory NF equipment using a flat sheet membrane with the effective area of 0.046 m2 and 96% sucrose rejection. Fat, protein, lactose and total solid content of the samples were analyzed by Infrared Milk Analyzer Bently 150. Ion composition of the samples was determined by ICP-MS instrument. The concentrations were carried out at different values of the ratio of the volume of dialyzation water and the volume of permeate (a ). The degree of demineralization of monovalent ions reached 70% and 90% at 2.5 volume concentration ratio, and at diafiltration and permeate volume ratios of 0.5 and 0.75, respectively. The amount of multivalent ions increased continuously during the NF combined with CVVD of acid whey. The rejection of the valuable compounds of whey such as protein and lactose was over 90%.

CVVD is more efficient to demineralize acid whey in case of a 00.75. The degree of demineralization of monovalent cations at a 0 0.75 and VCR 02.5 was approximately 90% while at a 00.5 it was 70%. No difference was observed between the concentration of total solid and lactose at different a value. On the basis of the presented results it can be concluded that the applied membrane is suitable for washing out of the monovalent ions and for concentration of valuable components like proteins, lactose, Ca, Mg and P ions in CVVD operation mode. / / / /