ABSTRACT DEES, AMANDA LEE. Effect of Various Ingredients on a Model Process Cheese System. (Under the direction of Dr. E. Allen Foegeding) The process cheese industry desires to increase formula flexibility by incorporating various alternative ingredients into process cheese. For example, incorporation of whey protein could reduce the amount of casein used in process cheese formulations. The purpose of this study was to understand effects of various ingredients and how they affect texture and meltability of cheese. The ingredients studied were native whey protein, mono- and disodium phosphate, lactose, and polymerized whey protein concentrate (pWPC). Cheese analogs contained mono- and disodium phosphate, lactose, 1 of 4 different whey protein ingredients or pWPC. Cheese analogs were made by heating and mixing for 21 min in a Stephan mixer with endpoint temperatures of 80°C or 85°C. The pWPC was prepared by heating WPC at 90°C, pH 8.0, for 30 min. Properties of pWPC were determined by small strain rheology. Cheese analogs were characterized by yield stress and meltability measurements. Native whey protein showed no clear trend with regard to yield stress or meltability. Also, the addition of lactose at 0% to 4.4% and mono- and disodium phosphate between 2.0% to 2.8% had no effect on yield stress while meltability results showed no consistent trend of cheeses cooked to 80°C. Differences were observed when cheese was heated to an endpoint of 85°C. The higher temperature increased yield stress approximately 80% and reduced meltability from a Schreiber number of about 9 to 5. Of four protein concentrations tested for polymerization, 5.0% and 4.5% protein had low viscosity, while 5.5% protein produced a texture similar to jelly. Generally, 6% protein formed a gel. A 13% substitution of casein with native WPC in a cheese analog resulted in a slight decrease in yield stress and no change in meltability. Whereas, a 13% substitution of casein with pWPC in a cheese analog increased the yield stress approximately 18% and decreased meltability from a Schreiber number of about 10 to 8. Different levels of lactose did not affect the texture or meltability of the process cheese analog, however, the level of mono- and disodium phosphate and whey protein did result in differences in yield stress and meltability. These differences were observed at a much greater extent when the cheese analog was cooked to a final temperature of 85°C. Abbreviation key: WPI = whey protein isolate, WPC = whey protein concentrate, pWPC = polymerized whey protein concentrate 2 EFFECTS OF VARIOUS INGREDIENTS ON A MODEL PROCESS CHEESE SYSTEM by AMANDA LEE DEES A thesis submitted to the Graduate Faculty of North Carolina State University in partial fulfillment of the requirements for the Degree of Master of Science DEPARTMENT OF FOOD SCIENCE Raleigh 2002 Approved by: ________________________ _______________________ E. Allen Foegeding, Ph.D. Chris Daubert, Ph.D. Chair of Advisory Committee __________________________ Mitzi Montoya-Weiss, Ph.D. 3 DEDICATION I would like to dedicate this thesis to four individuals who have inspired and led me throughout my 24 years of life. As with all families, we have had good times and bad but through it all we have loved each other and for that I could not ask for more. I would first like to dedicate this thesis to my Grandma, Aileene Stevenson Lee. It is through her unending support of all my whims and goals that have helped me get to this place in my life. Through her example I understand how important it is not to judge others and to know that basically everyone is doing their best and that is all that can be asked of a person. I find it interesting that the words “I love you” are rarely said but I have never doubted her love for me. I love her dearly. The second person I would like to dedicate this thesis to is my mama (Daddy, this is because I love her best!). She is the smartest person I know, and I admire the path she has chosen in life and am so grateful. She is responsible for bringing the family home to Pamlico so my sister and I could know our entire family. I couldn’t ask for a better gift. She has showed much strength and courage while still managing to smile. And I’m happy that my smile looks just like hers because I think she’s beautiful when she smiles. She has been a wonderful mother and I hope that one day I can be as good to my children as she has been to me. I love her dearly. The third person I would like to dedicate this thesis to is my daddy. I’ve never called him anything but daddy and he loves it. He is the most giving person I know. He has the ability to drive me crazy and make me laugh. I have many fond memories of four-wheeler riding and going to the dump. He has always been there when I needed him, from lunch at preschool to dinner at college. His favorite saying to me has been to “work hard now and play later”, and now I think it’s time to play. I love him dearly. And finally to Robbie, I have shared with him my past and will share my future with him. I have him to thank for so many wonderful college memories. I am so blessed to have such a smart and patient man to share my life with. I knew that one day I’d meet someone and probably get married, but I never thought that I’d have the ability to feel so connected to a person as I do to him. I love him dearly. ii BIOGRAPHY Amanda Lee Dees was born on November 26, 1977 in Raleigh, NC. She is the daughter of Gordon Dees and Judy Humphries. She also has one older sister, Ashley Johnson. Her family moved to Pamlico County, NC in 1980. After graduation from Pamlico County High in 1996, she attended North Carolina State University and obtained a B.S. degree in Food Science in 2000. She then began working towards her master’s degree also at NCSU under the direction of Dr. E. Allen Foegeding. iii ACKNOWLEDGEMENTS - I would like to express my sincere thanks to my family for all their support - I’d also like to thank Dr. Peggy Foegeding for being such an incredible role model and for leading me to my undergraduate advisor and my graduate advisor, Dr. E.A. Foegeding. - My sincere gratitude goes to Dr. E.A. Foegeding for his support, knowledge, and patience throughout my time at NC State. And also for sharing his family stories with me, so I could also learn about life and not just food science. - Thanks to Dr. Daubert for his expertise and advice throughout this project and for always being available to listen. - Additionally, thanks to Dr. Montoya-Weiss for her help and time invested in this work. - I’d also like to thank Paige Luck for everything regarding this thesis. She was instrumental in just about every aspect of this research project, and I couldn’t have done it without her assistance and encouragement. I’m happy to have gained such a good friend. - Thanks to Kraft Foods for funding this work and also giving me the opportunity for an internship. Dr. Ted Lindstrom, Dr. Heather Hudson, Patricia Rodriquez and Chris Pernell were extremely helpful during my time at Kraft. - Finally, to the lab group for making work interesting. I will take many fond memories and interesting stories. iv TABLE OF CONTENTS LIST OF TABLES..................................................................................................................vii LIST OF FIGURES...............................................................................................................viii PART 1: REVIEW OF LITERATURE...................................................................................1 Milk Protein..........................................................................................................................2 Casein................................................................................................................................2 Whey Protein....................................................................................................................7 Whey Protein-Casein Interactions..................................................................................10 Process Cheese....................................................................................................................11 Standard of Identity for Process Cheese and Substitute or Imitation Cheese.................12 Process Cheese Manufacture..........................................................................................16 Emulsification / Emulsifying Salts.................................................................................20 Whey Protein Incorporation............................................................................................22 Measurement Techniques...................................................................................................25 Yield Stress.....................................................................................................................25 Melting Tests..................................................................................................................29 Conclusions.........................................................................................................................31 PART 2. INTRODUCTION..................................................................................................37 PART 3. MATERIALS AND METHODS...........................................................................44 Material...............................................................................................................................45 Preparation of Process Cheese Analogs..............................................................................45 Preparation of Single Heated WPC Polymer......................................................................46 Preparation of Double Heated Polymer..............................................................................47 Process Cheese Analog Formula........................................................................................47 Whey Protein Incorporation................................................................................................47 Polymer Incorporation........................................................................................................48 Emulsifying Salts and Lactose Experiment........................................................................48 Large Strain - Yield Stress..................................................................................................48 Small Strain Rheology........................................................................................................49 Moisture..............................................................................................................................50 Meltability...........................................................................................................................50 pH........................................................................................................................................51 Protein Content...................................................................................................................51 Experimental Design...........................................................................................................51 Statistical Analysis..............................................................................................................51 PART 4. RESULTS AND DISCUSSION.............................................................................52 pH and Moisture.................................................................................................................53 Native Whey Protein Incorporation....................................................................................53 Emulsifying Salts Addition.................................................................................................55 v Lactose Addition.................................................................................................................58 Cook Temperature..............................................................................................................59 Commercial Process Cheese...............................................................................................60 Rheological Results from pWPC........................................................................................60 Polymerized Whey Protein Concentrate Addition..............................................................62 Conclusion..........................................................................................................................64 Recommendations for Future Research..............................................................................64 PART 5. LITERATURE CITED...........................................................................................66 PART 6. TABLES.................................................................................................................74 PART 7. FIGURES................................................................................................................79 vi LIST OF TABLES Table 1. Yield Stress, apparent strain, and Schreiber Number values of cheeses made with different native whey proteins..............................................................................75 Table 2. Yield stress, apparent strain, and Schreiber Number values of cheeses made with 4% whey protein isolate and various amounts of emulsifying salts (e. salts) with final cook temperatures of 80°C or 85°C..............................................................76 Table 3. Yield Stress, apparent strain, and Schreiber Number values of cheeses made with 4% whey protein isolate and various amounts of lactose with final cook temperatures of 80°C or 85°C...............................................................................77 Table 4. Yield stress, apparent strain, and Schreiber Number values of cheese analogs made with different pWPC...................................................................................78 vii LIST OF FIGURES PART 1: REVIEW OF LITERATURE Figure 1. Coat-core model of the casein micelle..................................................................32 Figure 2. Internal structure model of the casein micelle......................................................33 Figure 3. Subunit model of the casein micelle.....................................................................34 Figure 4. Action of emulsifying salt.....................................................................................35 Figure 5. 4-bladed vane and vessel dimension requirements...............................................36 PART 4: RESULTS AND DISCUSSION Figure 1. Heating curve for a process cheese cook cycle.....................................................80 Figure 2. Yield stress vs. pH of a process cheese analog containing 1% or 2% whey protein.. ................................................................................................................81 Figure 3. Yield stress vs. pH of a process cheese analog containing 4% whey protein isolate and various amounts of emulsifying salts.............................................................82 Figure 4. Yield stress vs. pH of a process cheese analog containing 4% whey protein isolate and various amounts of lactose.............................................................................83 Figure 5. Yield stress vs. pH for a process cheese analog containing different pWPC……84 Figure 6. Yield stress vs. moisture of a process cheese analog containing 1% or 2% whey protein ..................................................................................................................85 Figure 7. Yield stress vs. moisture of a process cheese analog containing 4% whey protein isolate and various amounts of emulsifying salts.................................................86 Figure 8. Yield stress vs. moisture of a process cheese analog containing 4% whey protein isolate and various amounts of lactose..................................................................87 Figure 9. Yield stress vs. moisture for a process cheese analog containing different pWPC. ………...................................................................................................................88 Figure 10. Yield stress and Schreiber Number for a process cheese analog containing 4% whey protein isolate and various amounts of emulsifying salts at 80°C or 85°C.89 viii