The innovation is important because surface contamination reduces operating efficiency, shortens run times and increases the likelihood of biofilm contamination, according to the researchers.
“Such fouling will result in decreased heat transfer rates, pressure fluctuations and an overall loss of product quality,” the paper states.
“Operating costs are further increased by frequent shutdowns for cleaning and the corresponding use of chemical detergents and sanitisers, which also increases the environmental load and impact.”
The coating was tested on the surface of 316L stainless steel heat exchanger plates, on which raw milk can be processed and which are subject to significant contamination, or fouling, of protein and minerals.
An electroless nickel plating process was used to co-deposit fluorinated nanoparticles on to these plates. The ability to resist fouling was demonstrated on a pilot plant scale heat exchanger.
The nanoparticle-modified steel surface slashed contamination by 97%, the researchers claimed in an article just published online in the journal Food and Bioproducts Processing.
While typical nanostructure approaches have been shown to be effective against fouling, they are limited by high cost and complex fabrication, often requiring a clean room and photolithography. Such fabrication requirements limit their potential for food industry applications, the scientists claim.
Physiochemical anti-fouling substances
In addition, many physiochemical anti-fouling substances have not been investigated for their ability to remain effective after repeated use, chemical abrasion and harsh conditions such as acidic foods and chemical cleaning agents.
By contrast, the coating devised by the scientists was found to have preserved its properties after 10 independent processing runs.
“Co-deposition of fluorinated particles during electroless nickel plating represents an effective and commercially scalable method to prepare anti-fouling coatings on stainless steel,” they conclude.
However, they call for ongoing work to demonstrate the long-term stability after repeated use, especially when exposed to thermal and mechanical stresses. And they say more tests at commercially relevant flowrates, temperatures and pressures are needed prior to commercial adoption of such a coating.
Source: 'Anti-fouling surface modified stainless steel for food processing'; Food and Bioproducts Processing; available online January 16, 2013; doi: http://dx.doi.org/10.1016/j.fbp.2013.01.003 ; Authors: Jeffrey Barrish; Julie Goddard; Department of Food Science, University of Massachusetts.