Egg Quality and Salmonella spp. Growth in Shell Eggs Packaged in Modified Atmosphere Packaging by Divya Aggarwal, B.S. A Thesis In FOOD SCIENCE Submitted to the Graduate Faculty of Texas Tech University in Partial Fulfillment of the Requirements for the Degree of MASTER OF SCIENCE Approved Leslie Dawn Thompson Chairperson of the Committee Christine Zocchi Alvarado Mindy Brashears Chance Brooks Karen Killinger Mann Fred Hartmeister Dean of the Graduate School May, 2008 Copyright 2008, Divya Aggarwal Texas Tech University, Divya Aggarwal, May 2008 ACKNOWLEDGEMENT I would first like to express my deepest gratitude to Dr. Leslie Thompson, my major professor, for giving me this opportunity to study at Texas Tech University, and work on this project, and for always supporting and encouraging me throughout this experience. She has been like a family to me in US. To my family for giving me endless support through good and bad. I would also like to express my appreciation to the other members of my committee, Dr. Christine Alvarado, Dr. Mindy Brashears, and Dr. Chance Brooks for their help and guidance throughout this project, Dr. Karen Killinger for her invaluable help in planning and standardizing the microbiology procedure, Ana Marie Luna for all her help with sample testing, data analysis, and overall support. I could not have done this without all of you. Lastly, but not the least, I would like to thank Cal-Maine Foods Inc. for donating the shell eggs used in this study and the USDA-ARS Nutrient Data Lab for funding the project. ii Texas Tech University, Divya Aggarwal, May 2008 TABLE OF CONTENTS ACKNOWLEDGMENTS ii ABSTRACT vi LIST OF TABLES viii LIST OF FIGURES xiii CHAPTER I. INTRODUCTION 1 II. LITERATURE REVIEW 6 US. Egg Industry 6 Egg Marketing 7 Egg Structure 8 Measurement of Shell Egg Quality 10 Modified Atmosphere Packaging 10 Commonly Used MAP Gases 12 Carbon dioxide in MAP 14 Effect of MAP on Microorganisms 16 Concerns about MAP 17 Egg Spoilage 18 Functional Properties of Egg 20 Hard-cooked Eggs 22 Yolk Surface Color 22 Salmonella 23 iii Texas Tech University, Divya Aggarwal, May 2008 III. METHODOLOGY 28 Egg Quality 28 Foam Capacity and Stability 29 Color Measurement 30 pH of Yolk, Albumen, and Whole Egg 30 Yolk Index 31 Haugh Unit 31 TBARS 31 Data Analysis 31 Microbiological Study 32 Sample Preparation 33 IV. RESULTS AND DISCUSSIONS 35 Color of Raw Albumen 35 Color of Raw Yolk 41 Color of Hard-cooked Albumen 52 Color of Hard-cooked Yolk Surface 68 Color of Inner Part of Hard-cooked Yolk 82 Peeling Property of Hard-cooked Shell Eggs 82 Foam Capacity 86 Foam Stability 87 Albumen pH 95 Whole Egg pH 101 iv Texas Tech University, Divya Aggarwal, May 2008 Yolk pH 101 Haugh Unit 111 Yolk Index 112 Microbial Quality of Eggs 124 Thiobarbituric Acid Reactive Substances (TBARS) 132 Conclusion 136 REFERENCES 138 APPENDIX v Texas Tech University, Divya Aggarwal, May 2008 ABSTRACT The effect of three types of modified atmosphere packaging (MAP) on the quality attributes and Salmonella spp. growth in oiled fresh USDA Grade AA shell eggs during storage was investigated. Shell eggs were subjected to one of four packaging treatments: (1) control - air; (2) 20% CO 2/0.4% CO/79.6% N 2; (3) 20% CO 2/80% O 2; and (4) 20% CO 2/80% N 2. Eggs were stored for up to 30 d, in a retail case at a temperature of 6 ± 1 C (refrigerated) or on shelves at 21 ± 1 C (abusive). Eggs were packed 8 to a tray with a tray considered as the experimental unit. Two trays per treatment per temperature per day were prepared in each trial with a total of three trials being conducted. Packages were opened and sampled on days (d) 1, 7, 14, 21, and 30 for determination of pH (yolk, albumen, whole egg), color (L*, a*, b*), TBARS, foam capacity and stability, Haugh units, and yolk index (YI). Data were analyzed by ANOVA in a 2 (temperature) x 4 (packaging treatment) x 5 (time-points) factorial design using programs in SAS. Where appropriate, means were separated by LSMeans. Whole egg pH was lower at both temperatures for the three MAP treatments (P < 0.05). Albumen pH for MAP treatments was significantly lower regardless of temperature as compared to the controls (P < 0.05). MAP treatment was effective at 6 C in maintaining lower yolk pH compared to control. A higher Haugh unit and yolk index throughout the storage at both temperatures was maintained by MAP treatment compared to the control treatment (P < 0.05). TBARS, and foam stability was similar for the MAP treatments and the control. Modified atmosphere packaging maintained higher foam capacity at both temperatures compared to control. Modified atmosphere packaging was effective in reducing egg deterioration and loss of functional quality during storage at refrigerated and abusive storage temperatures. vi Texas Tech University, Divya Aggarwal, May 2008 For the effect of three types of MAP treatments on Salmonella spp. growth in shell eggs, sanitized shell eggs, inoculated with 40 ul cocktail of Salmonella Enteritidis phage 13 nalidixic acid resistant, S. Heidelburg/ 3347, S. Typhimurium ATCC 14028 strains and concentration of 1 x 10 4 cells were subjected to four packaging treatments. Eggs were packed 6 to a tray and sampled on days 1, 7, and 14. Data were analyzed by ANOVA in a 2 (temperature) x 4 (packaging treatment) x 3 (storage time) factorial design using programs in SAS. Where appropriate, means were separated by Duncan’s multiple range test and main effects were studied. MAP treatments were similar in their effect on Salmonella spp. growth at both the storage temperatures in trial 1 and 2. However, in trial 3, at refrigerated temperature, air packed eggs had the lower Salmonella count than the three MAPs. At abusive temperature, high-ox treatment had higher Salmonella count (P < 0.05). vii Texas Tech University, Divya Aggarwal, May 2008 LIST OF TABLES 4.01 Raw albumen lightness, hue angle and chroma value ± SEM of eggs packed 36 in modified atmosphere packaging (20%CO 2/0.4%CO/79.6%N 2, 20%CO 2/80%N2, 20%CO 2/80%O 2), or air stored for 1, 7, 14, 21, 30 d at refrigerated (6 C) and abusive (21 C) temperature (n = 16) 4.02 Raw albumen lightness, hue angle and chroma ± SEM of eggs packed in 37 20%CO 2/0.4%CO/79.6%N 2 (CO 2/CO/N 2), 20%CO 2/80%N 2 (CO 2/N 2), 20%CO 2/80%O 2 (High-ox), or air stored at refrigerated (6 C) and abusive (21 C) temperature (n = 20) 4.03 Raw yolk lightness ± SEM of shell eggs packed in 42 20%CO 2/0.4%CO/79.6%N 2 (CO 2/CO/N 2), 20%CO 2/80%N 2 (CO 2/N 2), 20%CO 2/80%O 2 (High-ox), or air and stored for 1, 7, 14, 21, 30 d at refrigerated (6 C) temperature (n = 4) 4.04 Raw yolk lightness ± SEM of shell eggs packed in 43 20%CO 2/0.4%CO/79.6%N 2 (CO 2/CO/N 2), 20%CO 2/80%N 2 (CO 2/N 2), 20%CO 2/80%O 2 (High-ox), or air and stored for 1, 7, 14, 21, 30 d at abusive (21 C) temperature. (n = 4) 4.05 Raw yolk hue angle ( o) and chroma ± SEM of shell eggs packed in 44 20%CO 2/0.4%CO/79.6%N 2, 20%CO 2/80%N 2, 20%CO 2/80%O 2, or air and stored for 1, 7, 14, 21, 30 d at refrigerated (6 C) and abusive (21 C) temperature. (n = 16) 4.06 Raw yolk hue angle ( o) and chroma ± SEM of shell eggs packed in 45 20%CO 2/0.4%CO/79.6%N 2 (CO 2/CO/N 2), 20%CO 2/80%N 2 (CO 2/N 2), 20%CO 2/80%O 2 (High-ox), or air and stored at refrigerated (6 C) and abusive (21 C) temperature (n = 20) 4.07 Raw yolk chroma ± SEM of shell eggs packed in 46 20%CO 2/0.4%CO/79.6%N 2 (CO 2/CO/N 2), 20%CO 2/80%N 2 (CO 2/N 2), 20%CO 2/80%O 2 (High-ox), or air and stored for 1, 7, 14, 21, 30 d at abusive (21 C) temperature. (n = 4) 4.08 Hard cooked albumen lightness ± SEM of shell eggs packed in 54 20%CO 2/0.4%CO/79.6%N 2 (CO 2/CO/N 2), 20%CO 2/80%N 2 (CO 2/N 2), 20%CO 2/80%O 2 (High-ox), or air and stored for 1, 7, 14, 21, 30 d at refrigerated (6 C) temperature (n = 4) viii Texas Tech University, Divya Aggarwal, May 2008 4.09 Hard cooked albumen lightness ± SEM of shell eggs packed in 55 20%CO 2/0.4%CO/79.6%N 2 (CO 2/CO/N 2), 20%CO 2/80%N 2 (CO 2/N 2), 20%CO 2/80%O 2 (High-ox), or air and stored for 1, 7, 14, 21, 30 d at abusive (21 C) temperature. (n = 4) 4.10 Hard cooked albumen hue angle ( o) ± SEM of shell eggs packed in 56 20%CO 2/0.4%CO/79.6%N 2 (CO 2/CO/N 2), 20%CO 2/80%N 2 (CO 2/N 2), 20%CO 2/80%O 2 (High-ox), or air and stored for 1, 7, 14, 21, 30 d at refrigerated (6 C) temperature.