Présentée et soutenue par : Mme CHANTAL GHANEM le mardi 4 avril 2017 Study of the impact of oenological processes on the phenolic composition and biological activities of Lebanese wines Membre(s) du jury

Patricia Mme, M Taillandier, E Youssef, Rapporteurs Rayess, M Afram
unpublished
I express my respect and aknowledgement to Pr. Michel Aphram, the General Director of Lebanese Agriculture Research Institute (LARI). With his support, i realized my PhD and he gave me the opportunity to establish the first wine public laboratory in Lebanon. I also gratefully acknowledge Pr. Martine Mietton-Peuchot and Pr. Cédric Saucier for being external reviewers of this thesis, and Pr. Roger Lteif and Dr. Rita Yaacoub Nehmé for their acceptance to participate in the evaluation committee
more » ... ation committee Thank you in advance for your questions, suggestions and comments on my thesis. I express my sincere gratitude to my director Pr. Patricia Taillandier for giving me the opportunity to carry out my doctoral research and to be my supervisor throughout the development of this work. Her scientific advice and knowledge and many insightful discussions and suggestions helped me all the time during my experiments and thesis writing. I will always be grateful for everything that you have done for me. I express my sincere gratitude to my main supervisor Dr. Youssef El Rayess, for his advices, ongoing support, patience, motivation, enormous knowledge and all the useful discussions and brainstorming sessions, especially during the difficult conceptual development stage. I could not have imagined having a better advisor and mentor for my PhD study. I sincerely thank Pr. Jean Pierre Souchard who has agreed to supervise this thesis. His availability, attention, guidance and encouragement have been valuable for me. I would like to express for him all my gratitude and friendship. He's the funniest advisor I knew. I would like to thank Dr. Lara Hanna-Wakim, Dean of the Faculty of Agricultural and Food Sciences of USEK, and the staff of the faculty for their support and encouragement along my study. My sincere thanks also go to Dr. Jalloul Bouajila who gave me access to the laboratories in the Faculty of Pharmacy of Paul Sabatier University and research facilities. Without their precious support it would not be possible to conduct this research. I would like also to thank Dr. Nancy Nehmé for her valuable scientific advices. With you, Ziad and Youssef we will be a successful oenology research team. I would also like to thank the owner of chateau Saint Thomas Mr. Joe Touma for his great generosity, his cooperation and the quality of the wine he produces. These wines made from Lebanon an internationally recognized country by the number of medals which they win every year. Joe! I wish you the best! Ziad Rizk what can I say ... a sincere friendship which started from a very young age. Your help and support along my research project facilitated my task. With you, we can do a lot for our laboratory. Thank you to the team of the Faculty of Pharmacy of Toulouse, permanent and students for their help, support and friendship: Sylvie, Pierre -Luc, Salma, Mariam, Amin and Imen. Thank you for your advice in different techniques, you were always there when I needed help in the laboratory. I will never forget the good times spent with my colleagues at LARI laboratory. A special thought to Abdo, Fadia, Zinette, Dani, Carine, Elvis, Wassim, Jeanne and Rima. You made my years convivial My gratitude to my students: Samer, Jamila, Zaher, Rania, Myriam and Nour. You have helped me a lot in my experiences; I wish you all the success in your future work I cannot forget my friend Bilal Larnaout from Tunisia; you were always present when I needed help in France. Thank you for your friendship. I send a very special thanks to my husband Michel for his support and consistent encouragement. I thank him for always found the right words in difficult times and bringing me the comfort I needed Finally, to my father Nicolas, my mother Eugeuny and my brother Bernard, for all your love, and your support. They are no words to express the strength of my feelings and gratitude I have for you. Abstract The aim of this study was to determine the influence of different winemaking techniques on phenolic composition and biological activities of musts and wines from grapes of Syrah and Cabernet sauvignon from two distinct Lebanese regions (Bekaa valley and Chouf district) and two consecutive vintages (2014 and 2015). Among these processes the impacts of prefermentative cold and heating maceration, enzymatic treatment, two different commercial yeast strains and fining agents were discussed in our study. Spectrophotometric and HPLC analysis of phenolic compounds showed that the pre-fermentative heating maceration leads to a better extraction of phenolic compounds than the pre-fermentative cold maceration. Tannins and total polyphenols extraction are favored by the temperature and the prolongation of maceration. Extraction of anthocyanins is also favored by the temperature with short duration since the extension of the maceration leads to a degradation of these compounds. Maceration enzymes addition at early stage of maceration, promoted higher concentration of total polyphenol and antioxidant activity compared to those macerated without added enzymes. Alcoholic fermentation results in a decrease of total polyphenols content which revealed differences between wines derived from X and Y strains. After alcoholic fermentation, almost all of the wine samples presented an increase of their percentage of inhibition with the occurrence of new types of biological activities which doesn"t existed at must level. At the end, the results showed the importance of selecting a fining agent according to the type of wine and to minimize the dose of fining applied in order to conserve the content of phenolic compounds in wine.
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