Milk never sounded so good

Melbourne researchers are developing an ultrasound technology that could transform the Australian dairy industry by overcoming many of the difficulties currently encountered in dairy processing.

From the University of Melbourne's School of Chemistry, Dr Muthupandian Ashokkumar says the technology uses the high-frequency sound waves to generate chemical and physical interactions in milk and other dairy products, which leads to the modification of the dairy proteins. By doing this the team that includes Dr Muthupandian Ashokkumar, Dr Sandra Kentish, Prof Geoffrey Stevens (Chemical Biomolecular Engineering) and Prof Franz Grieser (Chemistry) hopes to improve and reduce the cost of common processes, such as heat stabilisation, used in dairy processing.

When ultra-high frequency sound waves (ultrasound) are passed through a liquid it generates a series of chemical and physical interactions in the liquid. Firstly, tiny micro-bubbles begin to form. The bubbles grow and shrink as each wave of sound passes through until eventually they grow to a critical size and implode. The imploded bubbles leave localised areas of heat and generate a sequence of reactions which begins with the production of radicals - pairs or groups of atoms bound together but incapable of surviving in this form, and looking for another atom or molecule to attach to. The whole process is called sonochemistry and has proved to have great potential for mani-pulating the structures of molecules and the chemical interactions that occur in liquids.

A collaboration of researchers from the University of Melbourne, Food Science Australia, Swinburne University of Technology and CSIRO Plant Industry were recently awarded $3.5 million from the Victorian government's Science, Technology and Innovation (STI) Initiative to explore the potential of ultrasound and other emerging technologies for use in the food industry in the Advanced Processing and Innovative Foods Program, which is also closely linked to CSIRO's Food Futures Flagship.

Dr Ashokkumar says, "By harnessing this technology to modulate the heat stability of dairy proteins, for example, we hope to greatly improve the effectivness and significantly reduce the cost of common industrial processes used in the manufacture of high-value dairy products."

Drs Ashokkumar and Kentish have also used ultrasound for the enhancement of the ultrafiltration technique. Ultrafiltration is a technique that is used to concentrate whey, a by-product of cheese making that can be otherwise difficult to dispose of due to the vast quantities produced.

Ultrafiltration works by passing the whey through porous membranes, which permits the separation of different proteins on the basis of their size. The problem is that, over time, proteins get lodged in the pores on the membrane surfaces, making it less effective as a membrane and less hygienic as a food processor. Early research by this team has already indicated that just 10 minutes of ultrasound is effective at removing the proteins that get lodged in the pores, suggesting it may be a useful technique for preventing membrane soiling during whey treatment in the dairy industry.