Date of Graduation

5-2015

Document Type

Thesis

Degree Name

Master of Science in Food Science (MS)

Degree Level

Graduate

Department

Food Science

Advisor/Mentor

Hettiarachchy, Navam S.

Committee Member

Seideman, Steven C.

Second Committee Member

Mauromoustakos, Andronikos T.

Third Committee Member

Kwon, Young Min

Keywords

Biofilms; Cantaloupe; E.coli; Organic acids; Salmonella; Spinach

Abstract

Outbreaks from the consumption of fresh produce are a concern in the United States. The consumptions of fresh produce have increased recently which expose a large segment of society to such outbreaks. Spinach and cantaloupe are minimally heated or processed before consumption which makes them a possible source of foodborne illness. The objective of this research was to investigate the effect of organic acids alone and in combination to reduce attached Salmonella Typhimurium (S.T) and Escherichia coli O157:H7 (E.coli) on spinach and cantaloupe, and to disintegrate biofilm formed by these pathogens by electrostatically spraying with two organic acids. To quantify the attachment, enumeration of attached bacteria was conducted. E.coli strains used in the study are ED 14, ED 15, ED 16, MD 46, MD 47, and MD 58. S.T strains used in the study are SD 10, and SD 11. E.coli ED 14 demonstrated the highest attachment property. Electrostatic spraying of organic acids showed that in spinach and cantaloupe lactic acid + malic acid at 2.0 % each showed the highest log reductions with 4.1 in spinach and 3.5 in cantaloupe, respectively. Strain dependency was observed in biofilm formation on spinach and cantaloupe homogenate using crystal violet assay. The images by confocal microscope showed the biofilm of E.coli and S.T was disintegrated by treatment with organic acids. Quorum sensing activity quantified by autoinducer AI-2 assay bases on the reporter strain V.harveyi BB 170 showed inhibition of the autoinducer compound by organic acid treatment.

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