Influence of fluid milk product composition on fouling and cleaning of Ni-PTFE modified stainless steel heat exchanger surfaces

This study aims to evaluate the influence of fluid milk product composition on both fouling and cleaning behavior of Ni-PTFE modified 316 stainless steel heat exchanger surfaces used in thermal processing. It is demonstrated that Ni-PTFE modification was effective in improving non-fouling properties of stainless steel surface, reducing fouling accumulation during thermal processing, and decreasing adhesion strength of foulant on heat exchanger surfaces. After two hours processing on a custom, benchtop scale heat exchanger, the Ni-PTFE modified 316 stainless steel coupons accumulated 2.64 ± 0.48, 5.28 ± 1.27, and 6.11 ± 0.24 mg/cm2 of fouling material for the thermal processing of raw whole milk, chocolate milk without carrageenan, and chocolate milk with carrageenan, respectively. The calculation of adhesion strength of fouling of the three milk products from both native and modified steel surfaces was in accordance with the experimentally determined results by fouling removal using a water jet method. Raw whole milk exhibited weaker adhesion strength on both native and modified surface when compared to the chocolate milk. The greatest water jet pressure required to remove the foulant from chocolate milk with carrageenan might be influenced by its carrageenan content, which led to the greatest adhesion strength to the stainless steel surface. These results will support commercial translation of Ni-PTFE non-fouling coatings, by enabling industrial practice to design effective clean-in-place (CIP) protocols based on product composition, and cost reducing current CIP protocols.