Lactose-free milk using graphene oxide membranes

The amount of disaccharide (lactose) in dairy foods varies between products; some cheeses contain virtually zero, while milk contains the most lactose of all the dairies at approximately 4–5 wt%. As a large portion of the world population is intolerant to lactose, there is an increasing demand for lactose-free milk.

Milk is usually delactosed through lactose hydrolysis, via enzymatic conversion into galactose and glucose. However, this process can increase sweetness and change colouring, and may decrease the nutritional value. A research group led by Aaron Morelos-Gomez of Shinshu University’s Global Aqua Innovation Center has now investigated the application of graphene oxide-based nanofiltration membranes for milk.

Graphene oxide membranes can create a porous foulant layer; therefore, their filtration performance was found to able to be maintained better than commercial polymeric membranes. The chemical and laminar structure of the graphene oxide membrane allowed an enhanced permeation of lactose and water while rejecting fat, proteins and some minerals. Therefore, the texture, flavour and nutritional value of milk were preserved better than with commercial polymer membranes.

Close-up of a graphene oxide membrane where lactose and water permeates through, leaving fat, proteins and large molecules in milk. Image credit: Aaron Morelos-Gomez, Shinshu University.

The concentration of lactose and lactose permeate flux was much higher than commercial nanofiltration membranes, due to the porous foulant layer and the laminar structure of the graphene oxide membrane. The irreversible fouling was improved by using a support membrane with 1 μm pore size for the graphene oxide membrane. This caused the formation of a porous fouling layer that allowed a higher recovery of water flux after milk filtration.

The research demonstrated that application of graphene oxide membranes provided good antifouling property and high selectivity for lactose, making it particularly suitable for dairy industry applications.

The method has a high potential for removing sugars from beverages while preserving other ingredients, therefore increasing their nutritional value. The high antifouling property against a solution rich in organic matter, such as milk, makes it potentially suitable for other applications such as wastewater treatment and medical applications.

The research group plans to keep exploring applications of graphene oxide membranes.

For more information about this research, the study ‘Graphene oxide membranes for lactose-free milk’ can be found in Carbon.

Top image credit: ©stock.adobe.com/au/anaumenko