Megan Ashley Marasco



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Listeria monocytogenes is a deadly human pathogen frequently found in dairy products. Its ability to grow and survive in the cold contributes to frequent contaminations despite the presence of food preservatives, such as propionate In my research, I first studied how effective propionate is against Listeria in dairy products, including three types of milk, 2%, fat free, and chocolate, all with and without propionate. Then I compared the survival of Listeria to survival of pathogenic E. coli in propionate-supplemented milk by monitoring the number of surviving bacteria 1, 2, and 3 days after storage in the refrigerator. I found that propionate is effective against Listeria only in 2% milk and is effective against E. coli only in fat free milk. Therefore, the efficacy of propionate depends on the types of dairy products as well as the types of foodborne pathogens. When one is developing food preservation methods, it is important to consider the different types of food and foodborne pathogens.

Publication Date


Project Designation

Independent Research

Primary Advisor

Yvonne Y. Sun

Primary Advisor's Department



Stander Symposium project

The Survival Rate of Listeria in Dairy Products Compared to Pathogenic E. coli