Applications abound for membrane-filtered milk.

Membrane processing is a proven separation technique utilized on the molecular and ionic levels for many years. Dairy processors have been successful in adapting membranes to treat whey and wastewater. More recently, researchers have explored using membrane filtration for fluid milk and using this milk to make dairy foods including cheese, ice cream mix and yogurt. Though current U.S. standards and labeling requirements do not allow such applications for membrane technology, their eventual use may offer new product opportunities in the United States and elsewhere.

Membrane separation could be attractive to processors of fluid milk because the technique demands little energy and does not destroy product during treatment. Four types of membrane filtration present potential applications for the dairy industry. These include reverse osmosis (RO), nanofiltration (NF), ultrafiltration (UF) and microfiltration (MF).

RO processing concentrates milk by removing water from the milk. UF and MF fractionate milk into various components. They can be used to standardize the nutritional value of consumer milk or to prepare standardized milk powders, overcoming natural variations in milk composition. Scientists have shown that increasing the protein content of skim and 1% milks by using UF makes the milk whiter, less blue and more viscous. Making the sensory quality of the product more similar to that of higher-fat milks improves its consumer appeal.

Other researchers have identified a small-pore MF process that fractionates non-fat milk into value-added protein ingredients. These include native casein concentrates from the retentate, pure milk serum proteins from the permeate and individual milk protein isolates that have application as emulsifiers, fortifying proteins and gelling agents.

The UF technique could find use in standardizing protein and total solids in milk used in fermented dairy foods, such as cream cheese and yogurt. Fermented products made with UF-processed milk have better quality and sensory characteristics compared with products made from milk concentrated by conventional processes.

Membrane filtration helps control quality attributes, such as consistency, post-processing acidification and extent of syneresis. However, using membrane-processed milk often requires an adjustment in starter culture selection and fermentation conditions.

Further information. Amy Skovsende, Dairy Management Inc., 10255 W. Higgins Rd., Suite 900, Rosemont, IL 60018; phone: [phone]; fax: [phone]; URL: http://www.extraordinarydairy.com.