Date of Award

2014

Document Type

Thesis

Degree Name

Master of Science (MS)

Department

Family and Consumer Sciences

First Advisor

Kang, Hye Won Dr.

Abstract

The prevalence of food contamination by pathogenic bacteria resulting in foodborne illness has raised concern to the food industry. In addition, oxidation in food, which affects the shelf life and quality of the food through the formation of off odor and off flavor, is another concern to the food industry. Nitrates, sulfates, benzoates of sodium and potassium, butylated hydroxytoluene (BHT) and butylated hydroxyanisole (BHA) are commonly used as preservatives in the food industry. However, long-term safety issues of synthetic preservatives in human health along with negative perception of consumers have lead researchers to find alternative natural preservatives. The purpose of this study is to find the most effective essential oil (EO) that has high inhibitory effect against pathogenic bacteria as well as high antioxidant activity among three commercially available EOs derived from armoise (Artemisia herba-alba), bay (Laurus nobilis) and rose geranium (Pelargonium capitatum x radens) plants. Antibacterial activity was tested against E. coli O157:H7 and Salmonella Typhimurium using growth over time assay and agar diffusion spot technique. The antioxidant activity was assessed using DPPH radical scavenging test, reducing power method and total antioxidant activity assay. Results showed that all three EOs showed antibacterial activity with different susceptibility. S. Typhimurium growth was completely inhibited by 0.2% of each EO whereas E. coli O157:H7 growth was completely prevented by 0.5% of each EO in growth over time assay. Among the three EOs, armoise exhibited the most effective inhibition against these two bacteria. However, rose geranium EO had the most effective inhibition against these bacteria in agar diffusion spot technique confirmed by the lowest minimum inhibitory concentration (MIC) and minimum lethal concentration (MLC). 2 These EOs also demonstrated antioxidant activity with highest effect in bay EO. Taken together, rose geranium EO efficiently inhibited both S. Typhimurium and E. coli O157:H7 growth through two different antimicrobial assays with moderate antioxidant activity. This indicates that rose geranium EO may be a potential candidate to be developed as a natural preservative in the food industry.

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