Degree

Doctor of Philosophy (PhD)

Department

School of Nutrition and Food Science

Document Type

Dissertation

Abstract

This study investigated the valorization of agricultural byproducts as sustainable sources of bioactive terpenes with potential applications in food preservation and nutritional enhancement. Seven agricultural byproducts such as sweet potato peel, cornsilk, sorghum bran, watermelon rind, honeydew peel, pineapple peel, and Perilla frutescens leaves were examined for their free and bound terpene contents using different extraction media. Polar solvents such as water and ethanol produced higher crude yields (2.9 ± 0.1% to 9.3 ± 1.0%; 3.1 ± 0.1% to 8.7 ± 1.1%) while acetone provided lower mass recovery (2.1 ± 0.1% to 8.4 ± 1.0%). Sweet potato peel and Perilla frutescens leaves were identified as rich sources of bound terpenes, emphasizing the significance of optimizing extraction and hydrolysis protocols to maximize the recovery and functional utilization of these bioactive compounds.

Perilla frutescens extracts were evaluated against major foodborne pathogens such as Listeria monocytogenes, Salmonella enterica, and Escherichia coli. The incorporation of free and bound terpenes from the Perilla frutescens extract into ground pork resulted in a significant reduction of Escherichia coli O157:H7 during refrigerated storage and confirmed their antimicrobial efficacy within complex food matrices.

The antioxidant activity of essential oils such as juniper berry, sandalwood, copaiba, and peppermint from Amazon were assessed in fish oil to evaluate their ability to stabilize polyunsaturated fatty acids (eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA). While copaiba and peppermint oils provided minimal oxidative stabilization (10.08 ± 0.10% and 3.88 ± 0.02%; 49.91 ± 0.35% and 14.96 ± 0.16%), sandalwood and juniper berry oils exhibited greater antioxidant performance (52.91 ± 0.15% and 34.02 ± 0.18 %; 47.88 ± 0.18 % and 45.79 ± 0.12 %) for EPA and DHA after 48 h. Their constituents, rich in oxygenated monoterpenes and sesquiterpenes, conferred strong radical scavenging and singlet oxygen quenching abilities. The acetone extract of Perilla frutescens displayed moderate antioxidant activity, reflecting the limited activity of bound terpene glycosides until hydrolyzed.

Finally, the findings of this study establish agricultural byproducts such as sweet potato peel, corn silk, watermelon rind, honeydew peel and pineapple peel as promising renewable sources of bound terpenes with dual antimicrobial and antioxidant functionalities.

Date

11-1-2025

Committee Chair

Dr. Zhimin Xu

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