Date of Graduation

5-2011

Document Type

Thesis

Degree Name

Master of Science in Food Science (MS)

Degree Level

Graduate

Department

Food Science

Advisor

Philip G. Crandall

Committee Member

Steven Ricke

Second Committee Member

Joshua Sakon

Keywords

Biological sciences; Antimicrobial; Beef; E. Coli; Essential oil; Inhibition; Temperature

Abstract

This research was undertaken to identify an antimicrobial for use during chilling in beef processing, including periods of temperature abuse, as well as to evaluate membrane filtration as means to remove essential oils from bacteria to prevent further antibacterial action. Cold pressed terpeneless Valencia orange oil was examined in combination with various temperatures (37°C, 10°C, and 4°C) to determine its antimicrobial activity against various strains of bacteria. The strains were tested using a ninety-six well microtiter plate method, with or without membrane filtration. The compound 2, 3, 5-triphenyl tetrazolium chloride was used as a growth indicator. Serial, two fold dilutions of the oil were tested. Plates were incubated at 37, 10, or 4°C for times up to 48 hours. Under the non-filtration method, 6 hours of exposure to the oil at 37°C, resulted in strains of E. coli O157:H7 being inhibited at oil concentrations ranging from 0.6% to 0.2%, with a mean of 0.4±0.01%. At 10°C, the O157:H7 strains were shown to be inhibited at concentrations ranging from 1.4 to 0.9%, with a mean of 1.1 ± 0.2%, after 6 hours. At 4°C, O157:H7 strains were inhibited after 6 hours at concentrations ranging from 4.6 to 2.3%, with a mean of 3.5 ± 2.1%. Under the membrane filtration method, E. coli O157:H7 was inhibited by cold pressed terpeneless Valencia orange oil at a concentration of 0.5±0.0%, L. monocytogenes at 0.5±0.0%, S. aureus at 0.31±0.13%, S.Typhimurium at 0.31±0.13%, S. sonnei at 0.75±0.29%, Y. enterocolitica at 0.31±0.13%, E. faecalis at 0.63±0.25%, B. cereus at 0.44±0.13%, and P. aeruginosa exhibited complete resistance to the oil. The ranges of MICs found under the non-filtration method appear to be the result of effects from the variable nature of a complex media and an antimicrobial that presents potential multiple mechanisms for inhibition of E. coli O157:H7 at refrigeration temperatures. The MICs found under the membrane filtration method were not significantly greater than those found by prior studies, indicating that membrane filtration is not required for determination of minimum inhibitory concentrations for essential oils.

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