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

  • Author / Creator
    Sanchez-Maldonado, Alma F
  • 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.

  • Subjects / Keywords
  • Graduation date
  • Type of Item
  • Degree
    Doctor of Philosophy
  • DOI
  • License
    This thesis is made available by the University of Alberta Libraries with permission of the copyright owner solely for non-commercial purposes. This thesis, or any portion thereof, may not otherwise be copied or reproduced without the written consent of the copyright owner, except to the extent permitted by Canadian copyright law.
  • Language
  • Institution
    University of Alberta
  • Degree level
  • Department
    • Department of Agricultural, Food, and Nutritional Science
  • Specialization
    • Food Science and Technology
  • Supervisor / co-supervisor and their department(s)
    • Andreas Schieber (Food Science and Technology)
    • Michael Gänzle (Food Science and Technology)
  • Examining committee members and their departments
    • Dr. Luke Howard (Food Science) University of Arkansas
    • Dr. Stephen Strelkov (Agricultural Food and Nutritional Science)
    • Dr. Marleny Saldaña (Agricultural Food and Nutritional Science)
    • Dr. Jonathan Curtis (Agricultural Food and Nutritional Science)
    • Dr. Michael Gänzle (Agricultural Food and Nutritional Science)
    • Dr. Andreas Schieber (Agricultural Food and Nutritional Science)