Evaluation of Microbial Dynamics on Low-Sodium Cooked Bologna Under Different Packaging Conditions
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Evaluation of Microbial Dynamics on Low-Sodium Cooked Bologna Under Different Packaging Conditions A Thesis Submitted To the College of Graduate Studies and Research In Partial Fulfillment of the Requirements For the Degree of Master of Science In the Department of Food and Bioproduct Sciences University of Saskatchewan By Maria F. Martínez Sepúlveda 2014 © Copyright Maria F. Martínez Sepúlveda, September 2014. All rights reserved. PERMISSION TO USE In presenting this thesis in partial fulfillment of the requirements for a Postgraduate degree from the University of Saskatchewan, I agree that the Libraries of this University may make it freely available for inspection. I further agree that permission for copying of this thesis in any manner, in whole or in part, for scholarly purposes may be granted by the professor or professors who supervised my thesis work or, in their absence, by the Head of the Department or the Dean of the College in which my thesis work was done. It is understood that any copying, publication, or use of this thesis or parts thereof for financial gain shall not be allowed without my written permission. It is also understood that due recognition shall be given to me and to the University of Saskatchewan in any scholarly use which may be made of any material in my thesis. Requests for permission to copy or to make other use of material in this thesis in whole or part should be addressed to: Head Department of Food and Bioproduct Sciences University of Saskatchewan, Saskatoon, Saskatchewan, Canada, S7N 5A8 i ABSTRACT The purpose of this study was to assess the growth of spoilage and pathogenic bacteria on low sodium concentration sliced cooked bologna under refrigerated storage conditions. In study 1, the effect of three different sodium concentrations (1%, 2% and 3%) and two packaging conditions (aerobic and vacuum) on growth of a cocktail of inoculated spoilage bacteria such Lactobacillus curvatus, Leuconostoc mesenteroides, Brochothrix thermosphacta and Pseudomonas fluorescens were investigated by using culture-dependent and culture-independent techniques. In general, reducing the sodium concentration from 2% (the current industry standard) to 1% NaCl in the cooked bologna system did not have a significant effect on microbial growth. The utilization of Ion Torrent high-throughput sequencing in this study allowed the description of the total microbial community present on sliced cooked bologna. Taxonomic analysis revealed the microbial community belongs to the phyla Firmicutes, Proteobacteria, Actinobacteria and Bacteroidetes. Finally, in this study, in situ meat redox measurement values were collected over time using platinum electrodes placed on top of, and in between bologna slices. While the redox values obtained were, in general, consistent with increasing bacterial cell numbers, issues of reproducibility and consistency were evident. The second study focused on the impact that the addition of a bacteriocin, Micocin X®, to the meat blend would have on growth of spoilage bacteria and in particular, Listeria monocytogenes, in vacuum-packaged cooked bologna formulated with 1% and 3% NaCl. In general, results demonstrated Micocin X® had a significant effect on the growth of Pseudomonas fluorescens and Listeria monocytogenes; however, no substantial effect was assessed in the control of lactic acid bacteria or Brochothrix thermosphacta. ii ACKNOWLEDGMENTS I would like to express my sincere gratitude to Dr. Darren Korber, my supervisor, for his academic guidance and support throughout the course of my study and research. I would also like to thank my advisory committee, Dr. P. J. Shand, Dr. T. Tanaka and Dr. R. Tyler for their valuable advice and contributions. A special thanks is extended to Dr. Gene Arganosa for serving as my external examiner. I also would like to acknowledge the technical assistance of Heather Silcox and Gerhard Maynard of the Department of Food and Bioproduct Sciences for their help during sausage production, as well as George Swerhone and John R. Lawrence of Environment Canada for their guidance during the redox potential measurements. I would especially like to thank my lab mates Ibi, Huda and Prabha for their time, unconditional support and good advice. I am also grateful to Mahbuba Ahsan and Marilyn Edrosolam for their assistance through the experiments. Special thanks to my parents who, with their encouragement, constant support and unconditional love, provided me the strength I needed to accomplish my dreams far away from home. Finally, I would like to sincerely acknowledge the Saskatchewan Ministry of Agriculture and the Alberta Livestock and Meat Agency for funding this project. iii TABLE OF CONTENTS PERMISSION TO USE .................................................................................................................... i ABSTRACT .................................................................................................................................... ii ACKNOWLEDGMENTS .............................................................................................................. iii TABLE OF CONTENTS ................................................................................................................ iv LIST OF FIGURES ...................................................................................................................... viii LIST OF TABLES ........................................................................................................................... x 1. INTRODUCTION..................................................................................................................... 1 1.1. General ................................................................................................................................... 1 1.2. Hypotheses ............................................................................................................................. 2 1.3. Objectives ............................................................................................................................... 2 2. LITERATURE REVIEW .......................................................................................................... 3 2.1. Meat quality ............................................................................................................................ 3 2.2. Meat shelf-life ......................................................................................................................... 3 2.3. Function of salt in meat products ............................................................................................ 3 2.4. Physical processing effects ..................................................................................................... 3 2.5. Sensory properties .................................................................................................................. 4 2.6. Preservative effect .................................................................................................................. 4 2.7. Health effects of salt ............................................................................................................... 4 2.8. Sources of sodium from meat products .................................................................................. 5 2.9. Processed meat ........................................................................................................................ 5 2.9.1. Meat curing ingredients ....................................................................................................... 5 2.9.2. Nitrite/nitrate ........................................................................................................................ 5 2.9.3. Sodium ascorbate or erythorbate ......................................................................................... 6 2.9.4. Phosphates............................................................................................................................ 7 iv 2.9.5. Sweeteners ........................................................................................................................... 7 2.9.6. Binders and extenders .......................................................................................................... 7 2.10. Reduction of sodium in processed meat ............................................................................... 7 2.11. Approaches to salt reduction in meat products ..................................................................... 8 2.12. Factors that influence microbial growth ............................................................................... 9 2.13. Packaging techniques.......................................................................................................... 10 2.13.1. Vacuum packaging .......................................................................................................... 11 2.13.2. Modified atmosphere packaging ...................................................................................... 11 2.14. Microflora of various ready-to-eat meat products .............................................................. 12 2.14.1. Fermented products .......................................................................................................... 13 2.14.2. Cured hams ...................................................................................................................... 14 2.14.3. Cooked meat ...................................................................................................................