Advances in Nonfouling Materials: Perspectives for the Food Industry Tiphaine Me ́ rian and Julie M. Goddard* Department of Food Science, University of Massachusetts, Amherst, Massachusetts 01003, United States ABSTRACT: Fouling of complex food components onto food-processing materials affects food quality, food safety, and operating efficiency. Developments in nonfouling and fouling-release materials for biomedical and marine applications enable the potential for adaptation to food applications; however, challenges remain. The purpose of this review is to present different strategies to prevent fouling and/or facilitate foulant removal with a critical point of view for an application of such materials on food-processing surfaces. Nonfouling, self-cleaning, and amphiphilic materials are reviewed, including an explanation of the mechanism of action, as well as inherent limitations of each technology. Perspectives on future research directions for the design of food processing surfaces with antifouling and/or fouling release properties are provided. KEYWORDS: nonfouling material, fouling release, protein repellent, self-cleaning, food processing ■ INTRODUCTION Fouling of food components onto food-processing surfaces (e.g., stainless steel, rubber gaskets, membranes, polymer or metal conveyor belts) reduces operating efficiency, shortens run times, and increases the likelihood of biofilm formation. As it pertains to the food industry, fouling can loosely be defined as the accumulation of minerals, proteins, and other food components on food-processing surfaces after prolonged submersion in liquid or semiliquid food products. In addition to providing a conditioning layer for the growth of pathogenic or spoilage biofilms, 1,2 fouling of food-processing surfaces has a substantial impact on processing efficiency, productivity, and food quality. Fouling is a particular issue in heat exchangers, where wall heating effects exacerbate foulant deposition (Figure 1). 3 As foulant builds up on the product side of a heat exchanger, thermal conductivity is reduced, increasing utility demands. 4 Foulant buildup is similarly an issue in membrane processes. In both cases, eventually, foulant thickness increases to a point that fluid flow is significantly affected, increasing pump demand to maintain flow rate. Once fouling has been initiated, continued buildup of food components results in the eventual need for cleaning. In many cases, foulant can be removed only by shutting down production, dismantling the unit, and manually cleaning the fouled equipment. In dairy processing, cleaning to remove foulant has been reported to be up to 15% of the total production time 5 and accounts for up to 80% of total production costs, 6 so the industrial economic impact of fouling on food-processing surfaces cannot be underestimated. A major challenge in the food industry is to avoid or minimize fouling caused by food components such as minerals and proteins during processing. This paper reviews recent advances in the design of nonfouling and self-cleaning materials. The following different approaches are described: protein-repellent surfaces, zwitterionic surfaces, stimuli-respon- sive polymers, the lotus effect, and amphiphilic materials. Finally, we critically evaluate challenges and opportunities toward possible applications of each approach to food processing. Mechanisms of Fouling on Food-Processing Surfaces. Despite the industry-wide impact of fouling on food-processing and -handling surfaces, the fundamental mechanisms by which fouling is initiated are not well understood. Several factors have been hypothesized to contribute to fouling in heat exchangers, including particulate deposition, protein content, mineral composition, and wall heating. 7 According to Epstein, 8 fouling mechanisms can be classified into five major categories, 8-10 including precipitation, partic- ulate, biofouling, corrosion, and chemical reaction fouling. It is unlikely that fouling is due to a single mechanism; rather, fouling likely involves a combination of several mechanisms occurring simultaneously. With regard to fouling by dairy products, two major classes of foulant are observed. Between 85 and 110 °C, a high protein content deposit forms, whereas at higher temperatures (110-140 °C) a higher mineral content deposit forms, consisting of calcium and phosphorus salts. 11 Received: November 18, 2011 Revised: January 25, 2012 Accepted: March 6, 2012 Published: March 6, 2012 Figure 1. Fouling on plate heat exchanger. Mineral and complex (protein, carbohydrate, lipid) foulants build up on the product-contact side of stainless steel in a plate heat exchanger. As the thickness of the foulant layer increases, heat transfer and operational efficiencies decrease. Review pubs.acs.org/JAFC © 2012 American Chemical Society 2943 dx.doi.org/10.1021/jf204741p | J. Agric. Food Chem. 2012, 60, 2943-2957