The produce we buy at the grocery store is exposed to a variety of environments and microorganisms before it ends up in our cart. But these microorganisms can spoil other produce, which can spread the contamination and the possibility of illness. To help prevent cross-contamination of produce, researchers at Texas A&M University have developed a coating that can be applied to anything that produces touches (belts, rollers, buckets, etc.). The coating is germicidal and acts as a water repellent. Bacteria need water in order to adhere to surfaces, so by creating a water repellent, it helps to reduce cross-contamination.
When produce is harvested, it is usually washed and sanitized with antimicrobials to kill any pathogens. Bacteria, however, can hide in the nooks and crannies of the skin. Currently, there are a few ways to prevent cross-contamination, including antimicrobial surface coatings. But the scientists say that the efficacy of these coatings decreases over time.
According to Mustafa Akbulut, associate professor in the Artie McFerrin Department of Chemical Engineering, "Consuming contaminated raw foods causes hundreds of people to get sick annually, and so food contamination is not only a huge health concern but is also a significant economic burden. In our study, we show that our new dual-function coating -- one that can both repel and kill bacteria -- can greatly mitigate bacterial spread, averting cross-contamination."
"Most bacteria can only survive in an aqueous environment," said Akbulut. "If surfaces are superhydrophobic, then water, and along with it most of the bacteria will be repelled away. With fewer bacteria around, less germicides are used up, increasing the overall lifetime of the coating."
To accomplish their goals, the scientists attached a thin layer of silica to an aluminum sheet and then added a mixture of silica and lysozyme (a germicidal protein), creating a coating that was rough in texture when viewed under a microscope.
"In general, if you increase roughness, the hydrophobicity of a material increases, but there is a limit," said Shuhao Liu, a graduate student in the College of Engineering and the primary author of the study. "If the coating is too rough, bacteria can once again hide behind crevices and contaminate. So, we tweaked the proportion of silica and lysozyme so that the roughness yielded the best possible hydrophobicity without compromising the coating's overall function."
When the researchers tested their coating against Salmonella typhimurium and Listeria innocua (two common disease-causing bacteria), they found that there was 99.99% less bacteria on these surfaces as compared to bare surfaces.
The results of the study are in the February issue of the journal ACS Applied Materials & Interfaces.