Functional Surfaces in Food Processing


Food contacts many inert surfaces that direct flow or induce turbulence during processing. These surfaces could be modified to provide additional capabilities. The feed spacer material of spiral-wound membranes used in dairy applications is one such surface that could be functionalized to mitigate bacterial growth.

Controlling bacteria is critical to a safe food supply. However, it has become more difficult as consumers demand lower levels of preservatives, such as salt (1). The dairy industry is seeking technologies to eliminate or mitigate the growth of bacteria, such as Listeria monocytogenes (LM), while meeting consumer demands (2). LM is of particular concern because it is especially lethal — in many cases, the mortality rate of LM infection is 25–30%. For example, raw milk cheeses contaminated with LM from Vulto Creamery in upstate New York infected eight people, including a newborn, and caused two deaths. The affected products were recalled, and the manufacturer was shut down (3).

Raw milk is pasteurized prior to further processing because it may contain LM and other microbial contaminants. However, the pasteurization process only destroys LM if it is properly applied. LM that remains or is reintroduced by contamination can be adsorbed or destroyed during downstream processing of milk using spiral-wound membrane elements that incorporate functionalized feed spacer materials. The feed spacer is composed of a temperature-resistant polymer mesh. The surface is chemically modified to promote LM adsorption, enabling antimicrobial agents immobilized on the surface to kill LM. Standard membrane cleaning methods can also kill adsorbed LM.

Functionalized meshes can be applied broadly in dairy plants for a range of milk and milk-based streams, including brine streams used in cheese making. The feed spacer mesh is an integral part of all spiral-wound membrane elements, and it can be applied with any membrane process, such as in ultrafiltration (UF) of raw milk. The mesh can also be used in the absence of a membrane in recirculating systems to inhibit LM growth. The modified material may be used in temperature-stable sanitary elements, and it may be steam-sterilized after LM adsorption and material saturation...

Author Bios: 

Stephen M. C. Ritchie

Stephen M. C. Ritchie, PhD, is an associate professor in the Chemical and Biological Engineering Dept. at the Univ. of Alabama (Tuscaloosa, AL) (Email: He has been working in the area of functionalized membranes since 1996. His research group has developed functionalized membranes for acid catalysis, protein fractionation, protein concentration, and affinity adsorption. He also spent two years as a visiting research scientist at Sepro Membranes (Oceanside, CA), where he worked to scale up functionalized membranes,...Read more

Mainara Costa-Teixeira

Mainara Costa-Teixeira earned her BS in chemical engineering in 2017 from Univ. Federal de São João del Rei, MG, Brazil. She is currently pursuing her PhD in chemical engineering at the Univ. of Alabama.Read more

Ryan M. Summers

Ryan M. Summers, PhD is a Reichhold--Shumaker assistant professor in the Chemical and Biological Engineering Dept. at the Univ. of Alabama (Email: He completed his postdoctoral research at the Center for Biocatalysis and Bioprocessing. His research focuses on metabolic engineering, synthetic biology, and biocatalysis for industrial microbiology applications. He earned a BS in biological engineering from Utah State Univ. and a PhD in chemical and biochemical engineering from the Univ. of Iowa.Read more

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