DEMINERALIZATION OF REHYDRATED CHEESE WHEY BY ELECTRODIALYSIS - EFFECTS OF DEASHING RATES AND SOLID CONCENTRATION ON LIMITING CURRENT-DENSITY

Regarding demineralization of rehydrated cheese whey by electrodialysis, the effects of deashing rates and of solid concentration on limiting current density were investigated. The electrodialyzer was composed of anion exchange membranes only. Limiting current density decreased with electric conductivity up to a 70% deashing rate. At higher deashing rate, limiting current density decreased sharply with the vanishing of Cl- ion content in the whey. When current density was close to the limiting density, ions were moved mainly by diffusion in the boundary layer on membrane surface and there remained only large anions of smaller diffusion such as PO4(3-), citric acid and lactic acid ions. When the solid concentration of whey was increased, limiting current density was mainly dependent on electric conductivity, not on solid concentration. This is because the viscosity of whey was increased and the degree of electrolytic dissociation decreased with increase in solid concentration.