dried meat other than sausages/salamis/jerky (e.g. meat powders, ..... Sorption (DVS) from Surface Measurement Systems (Middlesex, UK), ...... OWF in stomacher bags and stomached for 3 minutes (400, Seward, West Sussex, UK). ... Fisher 180 Scientific, Inc., PA) at 80°C. After reaching the set temperature, TAC cells were ...
INFLUENCE OF WATER ACTIVITY ON THE THERMAL RESISTANCE OF SALMONELLA IN LOW-MOISTURE FOODS
By RAVI KIRAN TADAPANENI
A dissertation submitted in partial fulfillment of the requirements for the degree of DOCTOR OF PHILOSOPHY
WASHINGTON STATE UNIVERSITY Department of Biological Systems Engineering DECEMBER 2017
© Copyright by RAVI KIRAN TADAPANENI, 2017 All Rights Reserved
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© Copyright by RAVI KIRAN TADAPANENI, 2017 All Rights Reserved
To the Faculty of Washington State University:
The members of the Committee appointed to examine the dissertation of RAVI KIRAN TADAPANENI find it satisfactory and recommend that it be accepted.
Juming Tang, Ph.D., Chair
Shyam Sablani, Ph.D.
Meijun Zhu, Ph.D.
Girish Ganjyal, Ph.D.
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ACKNOWLEDGMENT
First and foremost, I wish to express my heartfelt gratitude to my advisor, Prof. Juming Tang, for providing this incredible opportunity to pursue my doctoral study under his supervision. From the day I joined Prof. Tang’s research group, he has worked closely with me and has provided me the constant guidance, mentorship, and funding to make my PhD research productive and stimulating. From every meeting with him, I was motivated by seeing his joy and enthusiasm for the research problems and their potential solutions. Prominently, his invaluable advice on my research and career has shaped me into a skilled engineer. On a personal note, his balance of the professional and personal life with exceptional time management has immensely inspired me to improve myself for a better and disciplined life. I could not have imagined a better mentor for my PhD research. My sincere thanks to my thesis committee members: Dr. Shyam Sablani, Dr. Meijun Zhu, and Dr. Girish Ganjyal. I very much appreciate the time that the thesis committee has invested in the review of my research. I firmly believe that their insightful feedback has not only significantly enhanced the quality of this dissertation but also intellectually contributed to my development as a food engineer. I take this opportunity to thank Dr. Roopesh M. Syamaladevi who introduced me to the application of water activity in low-moisture food safety and provided me his perpetual mentorship during the early days of my research. I was very fortunate to work with him on the novel research ideas and gain considerable experience and research skills. Thanks to Dr. Rossana Villa-Rojas for providing her unwavering support and cheer during the challenges and achievements in my research.
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Many thanks to the gang of my beloved ‘Low-Moisture Food Safety Group.' Indeed, it was a remarkable opportunity for me to collaborate with every member of this group – Shuxiang Liu, Ren Yang, Jie Xu, Jaza Alshammari, Yuqiao Jin, and Marco Reyes Perez Esteban. Numerous discussions in the group and one-on-one meetings helped me in solving of the key issues which I had encountered in my research projects. Also, I was profoundly influenced by the research presented by my fellow colleagues which improved my dexterity significantly. I very much look forward to having these lab mates as colleagues in years ahead. One of the paramount moments in my PhD program was the internship at METER Group Inc., Pullman. I express my thankfulness to Dr. Brady Carter for this enriching opportunity. As an intern, I worked with his team (Mary Galloway, Andy Galbraith., and Zach Campbell) on some of their R&D projects. It is a matter of pride that from one of the internship projects, I was able to publish a peer-reviewed article which is now part of this dissertation. Also, this internship fortified me with new tools of a project initiation and management for which I am grateful to everyone at METER Group, Inc. Being part of student organizations has instilled pivotal leadership skills in me which I appreciate dearly. I indebted to the members of Food Engineering Club and WSU Cricket Club for backing me in the various projects which I spearheaded to improve the clubs’ image and recognition. I also extend my thanks to IFT- Food Engineering Division and ASABE – International Pre-Professional Committee for providing me the rewarding opportunities to be a part of respective leadership committees. I acknowledge the friendly and kind support of Stewart Bohnet, Huimin Lin, and Graham Barnett. They have been excellent lab staff and have offered help to me at every step of my research. Much thanks to Joanna Dreger, because of her timely reminders and assistance, my
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academic logistics were in the order. I also thank the staff of Department of Biological Systems Engineering for catering to the needs of graduate students and offering financial support in the form of scholarships and travel awards. My graduate program in Pullman was made memorable in large part due to many friends who became a part of my life. Space would run out to mention the names of all those special buddies, but I wholeheartedly thank all of you for listening, offering me advice and supporting me through this entire program. To my other friends scattered around the globe, I am gratified for receiving your thoughts and well-wishes. I am deeply obliged to my fiancé (and my alter ego): Dr. Innu Chaudhary for her unconditional love, encouragement, and tolerance during my PhD program. During ups and downs of my research, her confidence in me had got me going and succeed in the end. From the bottom of my heart, I thank her for sticking by my side and offering me the soul-strength in all my endeavors. Last but not the least, I want to thank my basic source of life energy: my family, for giving me life in the first place. My family had raised me with a love and a passion for science and always encouraged me to become a better and kind human being for the society. My parents and sister deserve special thanks as without their enduring love and support; I doubt that I would not have made it this far.
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INFLUENCE OF WATER ACTIVITY ON THE THERMAL RESISTANCE OF SALMONELLA IN LOW-MOISTURE FOODS
Abstract
by Ravi Kiran Tadapaneni, Ph.D. Washington State University December 2017
Chair: Juming Tang
Persistence of foodborne pathogens such as Salmonella in low-moisture foods (LMF) and its survival through thermal treatments and storage has caused a worldwide concern. In LMF, water activity (aw) influences the thermal resistance (D-value) of Salmonella. In previous studies on the D-values of Salmonella in LMF, inoculated LMF were treated in sealed test-cells/pouches at high temperatures while aw of LMF at the room temperature was reported. However, aw of LMF (at constant moisture content) in an enclosed system changes with the temperature, which may increase or decrease based on the sorption isotherms. But, there are limited aw measurement techniques at the elevated temperatures. In first study, a novel test-cell (TAC) was developed to evaluate the isolated influence of aw on the D-value of Salmonella in LMF. In TAC, stable relative-humidity (RH) (aw of LMF) was maintained at the elevated temperatures by using LiCl solutions of specific molality. D-values of Salmonella in organic wheat flour (OWF) under controlled RH environments were evaluated against the conventional thermal death time (TDT) cells. Results demonstrated that the stable aw
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in TAC significantly increased D-value of Salmonella in OWF (p 10 min). D-values of Salmonella in OWF from TAC II were observed to be significantly higher than the data from TAC and TDT cells (p
