Title page for ETD etd-10132005-152525


Type of Document Dissertation
Author Gaspar-Rolle, Maria Nelma Pinto
URN etd-10132005-152525
Title Attachment of bacteria to teflon and buna-n-rubber gasket materials
Degree PhD
Department Food Science and Technology
Advisory Committee
Advisor Name Title
Pierson, Mark D. Committee Chair
Bishop, J. Russell Committee Member
Eigel, William N. III Committee Member
Grayson, Randolph Larry Committee Member
Palmer, James K. Committee Member
Keywords
  • food contamination research
Date of Defense 1991-02-15
Availability restricted
Abstract
Surface analysis of buna-N-rubber and teflon was performed. Scanning electron microscopy was used to analyze the topography of both materials and x-ray microanalysis identified the elemental chemical composition of the polymers.

Teflon was primarily a smooth surface with random irregular spots, while buna-N-rubber had a very rough topography with "caverns" and crevices spread over the surface. The x-ray microanalysis showed that there are no impurities on the surface of teflon; however, calcium, silicone and sulfur were present on the surface of buna-N-rubber. Water contact angle measurements indicated that buna-N-rubber was a more hydrophobic surface than teflon.

Qualitative analysis of the attachment of Pseudomonas fragi A TCC 4973, Listeria monocytogenes Scott A and Bacillus cereus ATCC 11778 to buna-N-rubber and teflon was assessed by scanning electron microscopy. These bacteria readily attached to both surfaces. Pseudomonas fragi attached after 2 hours in the presence of this microoorganism and Bacillus cereus and Listeria monocytogenes attached at 12 and 24 hours, respectively.

Quantitative analysis of the attachment of Pseudomonas fragi to both surfaces as affected by various milk fat concentrations and temperature, and the availability of nutrients (different dilutions of skim milk, casein, casein and lactose, and whey and lactose) was conducted. Attachment was assessed by impedance microbiology. Milk fat content did not play a significant role in the process of attachment of this organism to either type of surfaces; however, significantly greater numbers attached to buna-N-rubber than to teflon. Overall bacteria attached in higher numbers to both surfaces when grown at 21°C, compared to bacteria grown at 4°C. For buna-N-rubber, bacteria attached in significantly higher numbers when the concentration of nutrients was minimal, while for teflon, the results were, in most cases, opposite to these.

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