Total Protein Isolate from Milk by Ultrafiltration: Factors Affecting Product Composition

¹ Department of Food Science, University of Illinois, 1302 West Pennsylvania Avenue, Urbana 61801

Skim milk (prepared from reconstituted NDM) was ultrafiltered by a combination of concentration and diafiltration to produce purified total protein isolates with the desired protein: lactose ratio. The rejection of protein and lactose followed expected trends. However, rejection of ash increased to 100% toward the end of the process due to insolubility of salts or their binding to proteins. At the natural pH of skim milk, the minimum ash content was 7 to 8% of the retentate solids, resulting in a limiting protein content of 90%.

Key Words: protein isolates • ultrafiltration • skim milk • lactose

Submitted on December 4, 1990
Accepted on March 7, 1991