University of Arkansas, Fayetteville ScholarWorks@UARK Theses and Dissertations 5-2012 Sanitation Assessment of Food Contact Surfaces and Lethality of Moist Heat and a Disinfectant Against Listeria Strains Inoculated on Deli Slicer Components Sabelo Muzikayise Masuku University of Arkansas, Fayetteville Follow this and additional works at: http://scholarworks.uark.edu/etd Part of the Food Microbiology Commons Recommended Citation Masuku, Sabelo Muzikayise, "Sanitation Assessment of Food Contact Surfaces and Lethality of Moist Heat and a Disinfectant Against Listeria Strains Inoculated on Deli Slicer Components" (2012). Theses and Dissertations. 355. http://scholarworks.uark.edu/etd/355 This Thesis is brought to you for free and open access by ScholarWorks@UARK. It has been accepted for inclusion in Theses and Dissertations by an authorized administrator of ScholarWorks@UARK. For more information, please contact [email protected], [email protected]. SANITATION ASSESSMENT OF FOOD CONTACT SURFACES AND LETHALITY OF MOIST HEAT AND A DISINFECTANT AGAINST LISTERIA STRAINS INOCULATED ON DELI SLICER COMPONENTS SANITATION ASSESSMENT OF FOOD CONTACT SURFACES AND LETHALITY OF MOIST HEAT AND A DISINFECTANT AGAINST LISTERIA STRAINS INOCULATED ON DELI SLICER COMPONENTS A thesis submitted in partial fulfillment of the requirements for the degree of Master of Science in Food Science By Sabelo Muzikayise Masuku Tshwane University of Technology Bachelor of Technology in Environmental Health, 2000 Curtin University Master of Public Health, 2005 May 2012 University of Arkansas ABSTRACT The overall objectives of this study were to: evaluate the efficacy of different cleaning cloth types and cloth-disinfectant combinations in reducing food contact surface contamination to acceptable levels; determine the optimum moist heat and moist heat + sanitizer treatments that can significantly reduce the number of Listeria strains on deli slicer components; and investigate if the moist heat treatment used in this study induced the viable-but-non-culturable (VBNC) state in Listeria cells. The efficacy of wiping cloths was measured using ATP-bioluminescence and total plate count methods using four different wiping cloths and silver dihydrogen citrate sanitizer on food contact surfaces. The lethality study of moist heat and silver dihydrogen citrate disinfectant against Listeria strains was done using deli slicer components and the viable-but-non-culturable state of Listeria strains subjected to sub-lethal moist heat and silver dihydrogen citrate disinfectant stresses was measured using BacLight bacterial viability test kit. In the first study we demonstrated that the cleaning effects of wiping cloths on food contact surfaces can be enhanced when used with the SDC sanitizer and stated that the ATP-B measurements can be used for real-time hygiene monitoring in the public sector with inclusion of microbial contamination testing (total plate count) for more reliable measure of cleanliness. In the moist heat lethality study, the internal moist heat only treatment and both the internal and external moist heat + disinfectant treatments yielded non- detectable levels of Listeria strains on stainless steel and cast aluminum coupons. Moist heat only and moist heat + disinfectant treatments at 150 °F (66°C) and at least 20% relative humidity (RH) for 5 h was adequate to attain non-detectable levels of a Listeria strains cocktail on both stainless steel and cast aluminum deli meat slicer components. The BacLight bacterial viability test demonstrated that the moist heat treatment applied in this study was effective in inactivating Listeria strains. However, the absence of growth on nutrient agar plates and detection of live cells by the viability test demonstrated that the sub- lethal temperature used in this study could induce the VBNC state in Listeria strains. This thesis is approved for recommendation to the Graduate Council. Thesis Director: Dr. Philip G. Crandall Thesis Committee: Dr. Steven C. Ricke Dr. Navam S. Hettiarachchy Dr. Jean-François Meullenet THESIS DUPLICATION RELEASE I hereby authorize the University of Arkansas Libraries to duplicate this thesis when needed for research and/or scholarship. Agreed __________________________________________ Sabelo M. Masuku Refused __________________________________________ Sabelo M. Masuku ACKNOWLEDGMENTS I am exceedingly indebted to my advisor, Dr. Philip G. Crandall for willing to accept me as his student and for providing me this chance and inspiration for this research. His overall direction, guidance and tolerance for my familial obligations have not gone unnoticed. Dr Elizabeth M. Martin, your enormous capacity for guiding, motivating and encouraging me throughout the course of my research has been amazing! I still can’t put my fingers on how you do it…with so much work in your hands and so many students who need your help, you were able to somehow “multitask” and help us whenever we needed you. I cannot forget to thank Dr. Dinesh Babu for stepping in at the right time and guiding me throughout my research with his expertise…you pushed me hard, but it was worth it! I also wish to thank my committee members: Dr. Steven C. Ricke, Dr. Navam S. Hettiarachchy, and Dr. Jean-François Meullenet, who were more than generous with their expertise and precious time as well as for agreeing to serve on my committee. Last but not least, I would like to extend my sincere gratitude to the Fulbright Scholarship Program for funding my studies in the USA; the Institute of International Education, particularly Emily Bosio, and the University of Arkansas Sponsored Students Program (Gloria Flores, Catherine Cunningham and their team) for their dedication to international sponsored students support. It’s been a long roller coaster ride but I finally made it! DEDICATION I dedicate this work and give special thanks to my wife and best friend, Sene, as well as our two wonderful kids Wami and Yenzo for their understanding and patience while I was away from them. You have all been my inspiration! A special feeling of gratitude goes to my loving mother, Juliet K. Masuku who did all she could for me to get to where I am today even before I knew I needed to go this far. Her words of encouragement and tenacity still echo in my ears. To my sisters and brother, guys thanks for being there as family and may God bless you exceedingly…you are very special. I also dedicate this thesis to my many friends out there who have supported me throughout the duration of my studies. Mduduzi Dlamini, I still recall the day you walked into my office to invite me to the interview that ended up bringing me here…God used you! Felix Masuku (Mnaketfu!), Mbulelo Dlamini (S’khutshwa), Andrew Dlamini and your families, thank you for teaching me what friendship is all about! TABLE OF CONTENTS PAGE CHAPTER I GENERAL INTRODUCTION ................................................................................................................. 1 Statement of the problem .................................................................................................................. 1 Study justification ............................................................................................................................. 2 Study objectives ................................................................................................................................ 3 Context of the study .......................................................................................................................... 3 Research question and hypothesis ..................................................................................................... 3 Assumptions ...................................................................................................................................... 4 Limitations ........................................................................................................................................ 5 Organization of the study .................................................................................................................. 5 REFERENCES ......................................................................................................................................... 6 CHAPTER II REVIEW OF LITERATURE ................................................................................................................... 8 Contamination of food contact surfaces ............................................................................................ 8 Significance of sanitary food contact surfaces .................................................................................. 8 Effects of food contact surfaces on cleaning efficacy ....................................................................... 9 Microbiological monitoring methods .............................................................................................. 10 Effectiveness of cleaning materials ................................................................................................. 11 Effectiveness of sanitizers ............................................................................................................... 12 Characterization and taxonomy of the genus Listeria ..................................................................... 13 Isolation and selective enrichment and plating ............................................................................... 15 Biochemical confirmation methods ...............................................................................................