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Mode of action, interaction and recovery of plant secondary metabolites for potential applications as food preservatives Open Access


Other title
Lactic acid bacteria metabolism of phenolic acids
antifungal glycoalkaloids
Mass spectrometry (MS)
Ultra fast performance liquid chromatography (UFLC)
water ethanolic extraction and separation of phenolic acids and glycoalkaloids
structure-function relationship of antimicrobial phenolic acids
Sterols in fungal membrane
Type of item
Degree grantor
University of Alberta
Author or creator
Sanchez-Maldonado, Alma F
Supervisor and department
Andreas Schieber (Food Science and Technology)
Michael Gänzle (Food Science and Technology)
Examining committee member and department
Dr. Luke Howard (Food Science) University of Arkansas
Dr. Andreas Schieber (Agricultural Food and Nutritional Science)
Dr. Michael Gänzle (Agricultural Food and Nutritional Science)
Dr. Jonathan Curtis (Agricultural Food and Nutritional Science)
Dr. Stephen Strelkov (Agricultural Food and Nutritional Science)
Dr. Marleny Saldaña (Agricultural Food and Nutritional Science)
Department of Agricultural, Food, and Nutritional Science
Food Science and Technology
Date accepted
Graduation date
Doctor of Philosophy
Degree level
Plants synthesize antimicrobial secondary metabolites that might have potential applications in food and pharmaceutical industries. Waste from food processing including peels, seeds, bark and cereal bran contain high amounts of these compounds. Their recovery from food by-products would be benefitial for the food industry, reducing costs and environmental damage. Phenolic compounds and glycoalkaloids are antimicrobial metabolites that coexist in plants of the Solanaceae family. However, in order to be efficiently utilized, their modes of action need to be completely elucidated. Furthermore, their recovery requires new sustainable and economically viable methods. This thesis partially elucidated the interactions between some of these compounds and their antimicrobial mechanisms of action. Moreover, an environmentally friendly method for their recovery from potato by-products was developed. The investigation of the structure-function relationship of antibacterial phenolic acids showed that their activity is enhanced at lower pH values. The antibacterial activity of hydroxybenzoic acids is more dependent on their hydrophobicity compared to hydroxycinnamic acids. The double bond on the side chain plays an important role on the antibacterial activity of hydroxycinnamic acids. Lactic acid bacteria metabolize phenolic acids likely as a strain-dependent detoxification mechanism. By studying the antifungal activity of potato secondary metabolites it was concluded that resistance to glycoalkaloids varies among fungal strains. Synergistic activity between phenolic acids and glycoalkaloids was found. The pattern of fungal sterols was related to their phylogenetic classification and to their resistance to potato glycoalkaloids. A method for recovery and fractionation of phenolic acids and glycoalkaloids from potato peels using water/ethanol solvents was developed. The crude extract contained mainly phenolic ii acids (chlorogenic, neochlorogenic and caffeic acids) and glycoalkaloids (α-chaconine and α-solanine). Solid phase fractionation allowed high recovery of glycoalkaloids and phenolic compounds. The phenolic acids fraction was free of toxic glycoalkaloids and, therefore, suitable for food applications. Alkaline hydrolysis of the crude extract followed by fractionation increased about five times the recovery of caffeic acid, enhancing the antimicrobial properties of the phenolic acids fraction.
Permission is hereby granted to the University of Alberta Libraries to reproduce single copies of this thesis and to lend or sell such copies for private, scholarly or scientific research purposes only. Where the thesis is converted to, or otherwise made available in digital form, the University of Alberta will advise potential users of the thesis of these terms. The author reserves all other publication and other rights in association with the copyright in the thesis and, except as herein before provided, neither the thesis nor any substantial portion thereof may be printed or otherwise reproduced in any material form whatsoever without the author's prior written permission.
Citation for previous publication
Sánchez-Maldonado, A. F.; Gänzle, M. G.; Schieber, A. (2011). Structure–function relationships of the antibacterial activity of phenolic acids and their metabolism by lactic acid bacteria. Journal of Applied Microbiology. 111, 1176-1184Sánchez Maldonado, A. F., Mudge, E., Gänzle, M. G.; Schieber, A. (2014). Extraction and fractionation of phenolic acids and glycoalkaloids from potato peels using acidified water/ethanol-based solvents. Food Research International, In Press, DOI: 10.1016/j.foodres.2014.06.018

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