University of Tennessee, Knoxville TRACE: Tennessee Research and Creative Exchange Doctoral Dissertations Graduate School 8-2014 Fabrication of Zein Nanoparticle-Biopolymer Complexes to Deliver Essential Oils in Aqueous Dispersions Huaiqiong Chen University of Tennessee - Knoxville, [email protected] Follow this and additional works at: https://trace.tennessee.edu/utk_graddiss Part of the Food Chemistry Commons Recommended Citation Chen, Huaiqiong, "Fabrication of Zein Nanoparticle-Biopolymer Complexes to Deliver Essential Oils in Aqueous Dispersions. " PhD diss., University of Tennessee, 2014. https://trace.tennessee.edu/utk_graddiss/2808 This Dissertation is brought to you for free and open access by the Graduate School at TRACE: Tennessee Research and Creative Exchange. It has been accepted for inclusion in Doctoral Dissertations by an authorized administrator of TRACE: Tennessee Research and Creative Exchange. For more information, please contact [email protected]. To the Graduate Council: I am submitting herewith a dissertation written by Huaiqiong Chen entitled "Fabrication of Zein Nanoparticle-Biopolymer Complexes to Deliver Essential Oils in Aqueous Dispersions." I have examined the final electronic copy of this dissertation for form and content and recommend that it be accepted in partial fulfillment of the equirr ements for the degree of Doctor of Philosophy, with a major in Food Science and Technology. Qixin Zhong, Major Professor We have read this dissertation and recommend its acceptance: Svetlana Zivanovic, P. Michael Davidson, Jun Lin Accepted for the Council: Carolyn R. Hodges Vice Provost and Dean of the Graduate School (Original signatures are on file with official studentecor r ds.) Fabrication of Zein Nanoparticle-Biopolymer Complexes to Deliver Essential Oils in Aqueous Dispersions A Dissertation Presented for the Doctor of Philosophy Degree The University of Tennessee, Knoxville Huaiqiong Chen August 2014 Copyright © 2014 by Huaiqiong Chen All rights reserved. ii ACKNOWLEDGEMENTS First and foremost, I would like to express my heartfelt gratitude towards my major supervisor Dr. Qixin Zhong for his guidance, patience, inspiration and encouragement throughout my study. Thanks for recruiting me as a student in his lab in the summer of 2011, even though I did not have any background in food science. I believe because of him, my career path changes to a different direction. In the past three years, he has been always very patient to me, and always supportable for anything I tried in the lab. I know how bad my first manuscript writing was and how much work he did to revise my manuscripts in the past three years. He always encouraged and helped me to improve my shortcomings and confidence. Because of his kind guidance and help I have made progress in the past three years. Additionally, because of the research assistantship provided by him, I was able to focus on doing research without considering financial problems. It has been my honor to be a student in his lab. I am also very thankful to my committee members, Drs. P. Michael Davidson, Svetlana Zivanovic, and Jun Lin for their time and efforts in helping me throughout my research. Thanks for your questions in the comprehensive exam that stretched my mind and got me thinking about new things. Thank you, Dr. Davidson for letting me doing microbial experiments in your lab and revising manuscripts. Dr. Zivanovic is the most elegant professor I have even met. She is so smart and her questions always make my heart rate increased, but I do learn many points from these nervous moments and especially from her class. Dr. Lin is a warm professor. Chatting with him made me feel how bright and supportive he is. iii I’d like to thank all my labmates, either already graduated or still in the lab: Minfeng Jin, Wan Wang, Linhan Zhang, Yue Zhang, Qiumin Ma, Jia Xue, Kang Pan, Xueqian Shi, Yun Zhang, Bai Qu, Kangkang Li, Dan Su, Yangchao Luo, Yongguang Guan, Gang Liu, Jiwang Chen, Jin’e Wu, Corina Rei, et al. I may forget to list some of you here. Overall, I am so happy that I can make friends with all of you in UT and I am also so grateful for your suggestions on my research when I had questions. The discussion with you guys in the lab cleared many of my confusions. I learned most of the instruments from you, especially Wan Wang, Yue Zhang and Kang Pan. Particularly, I’d thank Yue Zhang for doing antimicrobial experiments in Chapter 4, even though she was very busy at that time. I am indeed grateful for the faculties, staffs and graduate students in our department, who have made my life here full of love and happiness. I remembered Ann, Naucy and Davean pronounced my name as “Hawaii” on the first day I came to the department. So impressive! Because of this story, I think I should travel around Hawaii some day. Dr. Harte practiced for the whole semester during the class in order to pronounce my name correctly. So touched! Thanks, Dr. Philipus, for your patience in advising me on the use of instruments in our department. Thanks, Koi, Manpreet, Manessha, Vinay, Stella Chen, Cong Cao, May and other graduate students for chatting with me to improve my English. Last but not least, I owe my deepest gratitude to my family members. None of this would have been possible without the love and support from you. You have always been there for me in pursuit of my dream and career goal. iv ABSTRACT Zein, alcohol-soluble corn proteins, easily precipitate as nanoparticles after dispersing a stock zein solution with a polar solvent into water. The process can be used to nanoencapsulate essential oils (EOs). However, the stability of hydrophobic zein nanoparticles is a challenge for their application in aqueous food systems. The goal of this dissertation reseach was to stabilize zein nanoparticles in aqueous dispersions by forming complexes with water-soluble biopolymers. The stabilization of zein nanoparticles was first studied using sodium caseinate by dispersing hot 50% aqueous ethanol solution with both polymers in water. The nanoparticles contained κ-casein and zein, and the spray-dried nanoparticles were easily re-dispersed in water with good stability at pH 7.0 during storage. Before advancing to encapsulate EOCs, the distribution of free EO components (EOCs) in milk was studied in relation to their antimicrobial activity. It was found that, when the concentration of EOCs in the milk serum was above the minimum bactericidal concentration (MBCs) for Listeria monocytogenes Scott A (established in tryptic soy broth), complete inhibition was observed in milk. Conversely, when zein/casein complexes were used to co-encapsulate eugenol and thymol, the bactericidal effect against Escherichia coli O157:H7 and bacteriostatic effect against L. monocytogenes were observed at concentrations of EOCs in the milk serum well-below their corresponding MBCs. This suggested a maintenance of, and possible synergistic activity, of EOCs after nanoencapsulation. The spray-dried nanocapsules with co- encapsulated thymol and eugenol were easily hydrated in water as stable dispersions with particles smaller than 200 nm. Because zein/casein nanocomplexes were stable only at around neutral pH, gum arabic (GA) was also studied as another biopolymer to form v complexes with zein nanoparticles. Zein was pre-dissolved in propylene glycol, with peppermint oil as an EO model, and dispersed in water to form nanoparticles. The subsequent addition of GA formed nanocomplexes smaller than 200 nm and stable at pH 3.0-8.0. A gradual release of peppermint oil from freeze-dried samples was observed at pH 2.0-8.0, with a faster release at lower pHs. Therefore, water-soluble biopolymers such as caseins and GA can stabilize zein nanoparticles to enable the delivery of bioactive compounds in aqueous food dispersions. Key words: zein nanoparticles, sodium caseinate, gum arabic, nanocomplexes, essential oils, dispersion stability vi TABLE OF CONTENTS Chapter 1. Introduction and literature review ..................................................................... 1 1.1 Introduction ......................................................................................................... 2 1.2 An overview of essential oils .............................................................................. 2 1.2.1 Source and use of EOs .................................................................................... 2 1.2.2 Methods used to extract EOs from plants and plant parts .............................. 3 1.2.3 Compositions of EOs ...................................................................................... 4 1.2.3.1 Monoterpenes .......................................................................................... 4 1.2.3.2 Sesquiterpenes......................................................................................... 5 1.2.3.3 Phenylpropanoids .................................................................................... 5 1.2.4 Biological activity of EOs ............................................................................... 5 1.2.4.1 Antimicrobial activity ............................................................................. 5 1.2.4.2 Anti-viral activity .................................................................................... 8 1.2.4.3 Antioxidant activity ................................................................................ 9 1.2.4.4 Anti-carcinogenic activity ..................................................................... 10 1.2.5 Antimicrobial activity