Date of Graduation

12-2014

Document Type

Thesis

Degree Name

Master of Science in Food Science (MS)

Degree Level

Graduate

Department

Food Science

Advisor/Mentor

Morawicki, Ruben O.

Committee Member

Crandall, Philip G.

Second Committee Member

Ricke, Steven C.

Third Committee Member

Kwon, Young Min

Keywords

Aluminum; Listeria; Sanitizer; Slicer; Stainless Steel; Steam

Abstract

Listeria monocytogenes growth is of the greatest concern amongst ready-to-eat foods. The United States Department of Agriculture's Food Safety and Inspection Services determined that deli luncheon meats pose the greatest risk of contamination from L. monocytogenes Industrial meat slicers have many removable parts that are connected with sealers and gaskets, which can become worn over time. These spaces cannot be cleaned adequately, therefore are susceptible to bacterial growth. Planktonic cells form biofilms in order to protect the cell from adverse conditions, like during routine cleaning and sanitation. Once a biofilm is formed, the bacteria are much more difficult to eradicate and can be more resistant to the lethal effects of chlorine. This study analyzed the biofilm forming abilities of different L. monocytogenes serotypes and L. innocua by observation through motility tests, microtiter plate biofilm assay and microscopy. Listeria strains were grown on stainless steel coupons cut from a deli meat slicer blade in order the observe biofilm growth. This study also investigated the synergistic effects of steam and chemical sanitizers on disrupting and removing the biofilms formed on the stainless steel coupons. Both flagellated and non-flagellated Listeria strains produced biofilms and there was no correlation observed between the production of biofilms and hydrophobicity if the films. Overall there was a 5 to 7 log reduction between the combined treatments and the initial inoculation. The sanitizer alone gave a 2 to 3 log reduction and the steam treatment resulted in a 3 to 4 log reduction. The results of this study will provide better understanding of and potential methods for the sanitization of deli meat slicers. In turn, the knowledge gained from this study will reduce the risk of contamination and outbreaks of L. monocytogenes and other food-borne pathogens.

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