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Dairy science graduate wins SDSU Distinguished Master’s Thesis Award

Shivali Jindal counts spores
Graduate student Shivali Jindal counts biofilm colonies to determine which of four commercially available coatings is most effective at preventing microbe buildup and biofilm formation on heat exchange plates.

Dairy science graduate Shivali Jindal received the university’s 2018 Distinguished Master’s Thesis Award for research to prevent microorganisms from building up inside milk processing equipment. The $300 award, given by the SDSU Graduate School, recognizes scholarship and research.

Jindal, who completed her master’s degree in spring 2017, is an associate scientist at Nestle Nutrition in Grand Rapids, Michigan. She worked under the tutelage of professor Sanjeev Anand of the Dairy and Food Science Department. Jindal’s thesis will be considered for the national award sponsored by the Midwestern Association of Graduate Schools. The winners will be announced this spring.

Sanjeev Anand and Shivali Jindal
Professor Anand watches Shivali Jindal swab spore-forming bacteria from an AMC18 specimen.

For her thesis research, Jindal tested modified equipment surfaces to determine which is most effective at preventing microbe buildup and biofilm formation on heat exchange plates. She evaluated four commercially available coatings using three spore-forming Bacillus species commonly encountered in the dairy environment.

High levels of spore-forming microbes and their endospores, which can even survive pasteurization, adversely affect the flavor, texture and shelf life of milk products, such as cheese, yogurt and milk powders. Consequently, manufacturers must meet national and international food quality and safety guidelines for microbe levels in milk products, which then impacts their marketability.

The research was supported by grants from the National Dairy Council and the Midwest Dairy Foods Research Center, along with an active partnership with the U.S. Dairy Export Council. The project was done in collaboration with researchers at the University of Massachusetts-Amherst and Kansas State University.

The study results were first published in the December 2016 Journal of Dairy Science, with the article earning the “Editor’s Choice” designation. Additionally, the researchers have published two other articles and a third is under review.

To evaluate the coatings, Jindal identified which surface properties help prevent the microbes from attaching. While the surface roughness did not appear to affect bacterial adhesion, the surface energy and hydrophobicity influenced biofilm formation. “This is an area that people are trying to understand,” Anand said.

“If surface energy is less, fewer bacteria will attach to the surface, resulting in less biofilm formation,” Jindal said. Anand compared lowering surface energy to when a thin layer of ice coats a sidewalk. “When friction goes down, the affinity to attach goes down,” he said.

Conversely, an increase in hydrophobicity—the tendency of a droplet to maintain its shape, much like raindrops on a freshly waxed car—makes it more difficult for bacteria to attach. “Teflon is very hydrophobic,” explained Anand. “It alters the way the droplets interact with the material.” Further research is being conducted in Dr. Anand’s lab to understand similar properties of bacterial cell surfaces and their interaction with contact surface properties to understand the attachment behavior of sporeformers and endospores.

Of the four coatings evaluated, Ni-P-polytetrafluoroethylene produced the best overall results, meaning fewer bacteria adhered to the treated surface; while, Lectrofluor 641 also exhibited low surface energy and high hydrophobicity.

Through this study, the researchers gained a better understanding of the surface characteristics that discourage microbe attachment. “We cannot eliminate the microbes, but we can decrease them,” Anand said. This will then help reduce spoilage and improve the quality of dairy products. In addition, this research will also have an impact on dairy processing equipment functioning.

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