Ethanol Extraction of Lactose from Nonfat Dry Milk: Production of Protein Raffinate

Abstract

The efficiency of extracting lactose from NDM with aqueous ethanol was investigated under conditions where four factors were varied. The experiments were conducted in a complete random block design using three values for each of the variables: ratios of solvent to solids 10:1, 15:1, and 20:1 (wt/wt); solvent ethanol content of 62.4, 72.9, and 84.0% (wt/wt); temperature during extraction of 10, 25, and 50°C; and added divalent metal ion chelator (citrate) in the amount of 0, 10, and 20 mmol/100g NDM. The results were evaluated statistically using response surface methodology with a multivariate linear regression equation. Optimal extraction efficiency was obtained with high ratio of solvent to solid and low ethanol concentration of the solvent. High temperatures and high citrate concentrations tended to solvate proteins and make separation by filtration difficult. Milk protein with residual lactose of 2 to 4% was obtained using this one-step extraction process under optimal conditions.