2D Material Membranes for Lactose-Free Milk

Graphene oxide membranes allow milk to be filtered to get rid of lactose molecules while maintaining more nutritional value than commercial polymer membranes. Other applications may include wastewater treatment and purifying blood in medical applications.
Image rendered and produced by Dr. Aaron Morelos-Gomez
September 6, 2021

Since 2015, the United Nations has established a series of goals to achieve peace and prosperity, known as the sustainable development goals. Among these goals are “good health and well-being”, and “industry, innovation, and infrastructure”. With Frontier Materials, it is possible to find solutions with high potential to address these goals.

There is a large population that is intolerant to lactose

Milk is a well-known source for protein, calcium and carbohydrates, and is highly present in the diet of many cultures. However, there is a large population that is intolerant to lactose and may miss this source of high calcium content. To overcome this issue, lactose is commonly removed through an enzymatic process. Unfortunately, this process may increase sweetness, change coloring and hinder its nutritional value. An alternative method involves the use of membrane technology. Typically, a two-step process is involved. First, an ultrafiltration membrane is used to separate most of the lactose and proteins, and then a nanofiltration membrane is used to remove the remaining lactose.

Membrane technology still requires development to meet the demands of particular applications. In the food industry, the attachment of organic matter on the membrane surface, known as fouling, can decrease the separation performance. Unfortunately, commercial membranes are prone to fouling due to their surface roughness and hydrophobicity. Therefore, Frontier Materials are needed to simultaneously overcome fouling and provide a high separation performance.

2D materials are atomically thin, and have an extremely low surface roughness. This makes it difficult for other materials to build up on its surface. Among all the 2D materials, graphene oxide can be produced in large quantities because it is produced from graphite where the individual graphene layers are separated and oxidized simultaneously. This yields a 2D material that can be handled easily in water. We took advantage of this property to produce graphene oxide (GO) membranes by spray-coating. A method that can be easily scaled up.

These membranes can even be explored for applications in medicine to purify blood

To understand the capabilities of GO membranes, we compared its milk filtration performance against commercial ultrafiltration and nanofiltration membranes. Here, the fouling and lactose separation were studied. Intriguingly, the GO membrane developed a porous fouling layer due to its chemical structure and the micrometric pores within the membrane that supports the layer of GO. In addition, computer simulations demonstrated that lactose has a low interaction with GO. The measured lactose permeate flux using a GO membrane had up to two times higher the lactose permeate flux when compared with commercial ultrafiltration and nanofiltration membranes.

The unique porous fouling layer and the low interaction between lactose and GO, allow lactose to easily flow across the GO membrane along with water. Whereas, fat and proteins can remain in the milk source, and retain the taste and texture of milk. On the other hand, other methods for treating lactose in milk can alter its taste, texture and even color. It is important to maintain these qualities to achieve lactose-free dairy products that taste like their counterparts including lactose.

These GO membranes have demonstrated to be effective in separating sugars such as lactose, and opens the possibility for their application to remove sugars from other beverages such as juice and wine. In addition, its high fouling resistance makes it ideal for wastewater treatment, which has a high content of organic matter. These membranes can even be explored for applications in medicine to purify blood or other samples for analysis.

References:

  • Morelos-Gomez, Aaron, et al. "Effective NaCl and dye rejection of hybrid graphene oxide/graphene layered membranes." Nature Nanotechnology 12.11 (2017): 1083-1088.
  • Morelos-Gomez, Aaron, et al. "Graphene oxide membranes for lactose-free milk." Carbon 181 (2021): 118-129.

Author

Dr. Aaron Morelos-Gomez

Associate Professor at Shinshu University, Japan
Aaron is a specialist working on graphene oxide and polyamide membranes for water filtration. He also has extensive academic and industry experience working on carbon nanomaterials.
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