Date of Graduation

12-2016

Document Type

Thesis

Degree Name

Master of Science in Food Science (MS)

Degree Level

Graduate

Department

Food Science

Advisor

Navam S. Hettiarachchy

Committee Member

John Marcy

Second Committee Member

Han Seok Seo

Abstract

Essential oils derived from the bark and leaves of the cinnamon plant have long been used as natural preservatives and flavoring agents in different types of foods. In this study, we evaluated the antimicrobial effects of cinnamon essential oils (CEOs), obtained from cinnamon leaf or bark, against two foodborne pathogens i.e., Salmonella Typhimurium (S.T.) and Listeria monocytogenes (L.m.). Two different concentrations of microbial loading were used i.e.,109 and 104, cultured in nutrient media broth, strawberry shakes, and on celery sticks. Both CEOs of leaf and bark at 0.5% and 1% were found to completely inhibit S.T. and L.m., immediately after addition to the cultures. Based on the results of the broth culture experiments, we also investigated the antimicrobial effects of the CEOs at 0.5% and 0.1% in strawberry shake, against S.T. and L.m. Again when 0.5% (v/v) of the CEOs were added to the strawberry shake and stored at 4oC, both bacteria were found to be completely inhibited after a storage period of 8 days. The strawberry shakes containing CEOs from bark had higher ratings of sensory acceptability compared to those containing leaf CEOs, with or without the addition of masking agents. When 0.5% (v/v) of CEOs from leaf were applied on celery, the results showed a higher log reduction for L.m. (1.0 and 3.9 CFU/mL) for both 109 and 104, as compared to S.T for which the reductions were 0.88 and 2.85 CFU/mL, after a storage period of 7 days at refrigeration temperature. For celery samples applied with 0.5 % (v/v) CEO of bark, the reductions were 1.1 and 3.8 CFU/mL for L.m and 1.2 and 3.5 CFU/mL for S.T, at low and high bacterial concentrations, respectively.

Overall, this study demonstrates that CEOs derived from bark are better than those derived from leaf with respect to antimicrobial activity and sensory aspects. Hence cinnamon essential oils of leaf and bark can be used as a potential antimicrobial agent to keep fresh produce and milk beverages safe for human consumption.

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