Characterisation of the rheological properties of mozzarella cheese 135p

Copyright is owned by the Author of the thesis. Permission is given for a copy to be downloaded by an individual for the purpose of research and private study only. The thesis may not be reproduced elsewhere without the permission of the Author. COLLEGE OF ENGINEERING TE KUPENGA O TE MĀTAURANGA CHARACTERISATION OF THE RHEOLOGICAL PROPERTIES OF MOZZARELLA CHEESE A THESIS PRESENTED IN PARTIAL FULFILMENT OF THE REQUIREMENTS FOR THE DEGREE OF MASTER OF ENGINEERING IN CHEMICAL AND BIOPROCESS ENGINEERING AT MASSEY UNIVERSITY, MANAWATU, NEW ZEALAND CHANGJUN ZHU 2013 I ABSTRACT An important usage of Mozzarella cheese is as an ingredient in pizza. For this reason, it is important to understand the functional properties of melting and flow behaviours of mozzarella cheeses. For instance, understanding the influence of temperature and moisture on the rheological properties of mozzarella cheese may help cheese the maker to optimise products. A modified UW Meltmeter and rotational methods were used to characterise the rheological properties of mozzarella cheese. The temperature impact on the rheology was determined by measurement over the temperature range from 30 to 80 °C. To investigate the moisture content effect on the rheological properties, mozzarella cheese was dried over different salt solutions or by desiccation in a fridge prior to rheological measurement. Modifications of the UW Meltmeter improved the sample preparation, temperature control during the testing and data analysis. The viscosity data obtained by the UW Meltmeter followed the Arrhenius law with an activation energy of 30.3±1.2 ή ‘Žିଵ. In the rotational method (the shear rate ramp test), the data of viscosity versus shear rate followed the power law model, and the consistency index was fitted to the Arrhenius law and WLF model. The WLF model had a wider temperature range fit than the Arrhenius law. It was found that the viscosity determined from the UW Meltmeter and rotational rheometer was quite different. They are actually measuring different aspects of flow. In this study, the rotational experiment produced results that were more appropriate to explain flow behaviour in cheese in the conditions experienced in pizza baking. The methods to lower the moisture content of mozzarella cheese led to unexpected results where viscosity was not strongly dependent on moisture content. This may have been due to disruption of the structure of the mozzarella cheese during drying.II ACKNOWLEDGEMENTS It is a great journey through the Master study. There were many challenges for me to study abroad, fortunately I got a lot of helps and supports here from my supervisors, friends, family and some kind people. With these people help and support, I learned a lot and finished my Masters. Firstly, I would like to thank my supervisor, Professor John Bronlund, for giving me this opportunity to do this study, teaching me how to arrange a project, helping me to address some project problems, and guiding me through my experimental works and thesis writing. Big thank to my supervisor, Dr. Colin Brown, who help me a lot in experimental works, discussion of any difficulties and especially the revision of my thesis. I appreciate his patience to revise my thesis word for word. I gratefully acknowledge my Fonterra supervisor, Dr. Phillip Watkinson, for the training of the UW Meltmeter, his advice and discussion, and the help in my milestone reports and thesis. I would like to thank my Fonterra supervisor, Dr. Graeme Gillies, for the training the rotational rheometer, sharing some helpful knowledge and editing of my thesis. Thanks to Fonterra for funding this project and providing the equipment. I appreciate all people in the PGP group for some suggestions and discussions. I am also very grateful to the laboratory technicians, John Edwards and Ann-Marie Jackson for the help in lab, the electronics technician, Anthony Wade, and workshop technician, Clive Bardell, for the device developments. Thanks to all the people who helped me. ᴰਾˈᝏ䉒ᡁⲴ⡦⇽ˈᵡݹ㭑઼⊏⌇⨐ˈаⴤԕᶕሩᡁⲴᮉሬ઼᭟ᤱˈᝏ 䉒ԆԜ㔉ᡁᨀ׋䘉⅑⮉ᆖⲴᵪՊDŽᝏ䉒ᡰԕޣᗳᡁⲴӢᴻྭ৻DŽIII Contents ABSTRACT ................................................................................................................................... I ACKNOWLEDGEMENTS ............................................................................................................. II LIST OF TABLES ....................................................................................................................... VIII LIST OF FIGURES ....................................................................................................................... IX 1. BACKGROUND AND OBJECTIVES ...................................................................................... 1 1.1. Background ............................................................................................................. 1 1.2. Objective of project ............................................................................................... 2 2. LITERATURE REVIEW ......................................................................................................... 3 2.1. Introduction ............................................................................................................ 3 2.2. Melting cheeses ...................................................................................................... 3 2.2.1. Cheese composition and structure................................................................... 3 2.2.2. Functional properties of melting cheese ......................................................... 5 2.2.3. Mechanism for melting ..................................................................................... 5 2.2.4. Factors effecting melting performance ............................................................ 7 2.2.4.1. Temperature .................................................................................................. 7 2.2.4.2. Moisture ........................................................................................................ 8 2.2.4.3. Fat .................................................................................................................. 9 2.2.4.4. Calcium .......................................................................................................... 9 2.3. Rheology ................................................................................................................ 10 2.3.1. Types of rheological behaviour ...................................................................... 10 2.3.1.1. Newtonian fluids .......................................................................................... 10 2.3.1.2. Shear thinning flow behaviour .................................................................... 11 2.3.1.3. Shear thickening flow behaviour ................................................................. 12 2.3.1.4. Plastic flow behaviour (Bingham plastic and viscoplastic). ......................... 12 2.3.2. Rheometry methods ....................................................................................... 13 2.3.2.1. Capillary viscometers ................................................................................... 14 2.3.2.2. Rotational viscometers ................................................................................ 14 2.3.2.3. Oscillatory rheometer .................................................................................. 15 IV 2.3.2.4. Squeezing flow viscometry .......................................................................... 15 2.4. Methods to measure flow during melting ....................................................... 16 2.4.1. UW Meltmeter ................................................................................................ 16 2.4.2. The Arnott test ................................................................................................ 19 2.4.3. The Schreiber test ........................................................................................... 19 2.5. Mozzarella cheese making ................................................................................. 20 2.5.1. Milk quality ..................................................................................................... 20 2.5.2. 2.5.2 Thermal treatment ................................................................................ 20 2.5.3. Curd formation ................................................................................................ 21 2.5.3.1. Calcium addition .......................................................................................... 21 2.5.3.2. Acid development ........................................................................................ 21 2.5.3.3. Rennet-Catalyzed coagulation ..................................................................... 21 2.5.4. Cutting ............................................................................................................. 21 2.5.5. Stretching ........................................................................................................ 22 2.5.6. Molding ........................................................................................................... 22 2.6. Conclusion ............................................................................................................. 22 3. UW MELTMETER METHOD DEVELOPMENT ................................................................... 24 3.1. Introduction .......................................................................................................... 24 3.2. Estimation of key process conditions during pizza baking ......................... 24 3.3. Sample preparation ............................................................................................ 25 3.3.1. Current cheese sample template ................................................................... 26 3.3.1.1. Cut quality for the current sample template ............................................... 26 3.3.1.2. Results for sample variation in standard template ..................................... 27 3.3.2. New cheese sample template design ............................................................. 27 3.3.2.1. Cut quality for the new sample template .................................................... 28 3.3.2.2. Results and comparison with the old template ........................................... 28 3.3.3. Procedures for UW Meltmeter test ............................................................... 29 3.4. Temperature distribution in the UW Meltmeter ........................................... 30 3.4.1. Choice of mozzarella analogue ....................................................................... 31 3.4.2. Temperature of cheese sample during testing .............................................. 31 V 3.4.3. Results ............................................................................................................. 32 3.4.3.1. Halloumi deformation during the test ......................................................... 32 3.5. UW Meltmeter modification .............................................................................. 36 3.5.1. Top plate modification ................................................................................... 36 3.5.2. Testing effects of insulation ........................................................................... 37 3.5.3. Results ............................................................................................................. 37 3.6. Data analysis method .......................................................................................... 38 3.6.1. Biaxial stress growth coefficient calculation ................................................. 38 3.6.2. Regression model for height vs. time ............................................................ 39 3.7. Mozzarella anisotropy and the impact of cheese sampling ........................ 43 3.8. The effect of EPS modification on rheological property .............................. 46 3.9. Conclusion ............................................................................................................. 48 4. UW MELTMETER RESULTS .............................................................................................. 49 4.1. Introduction .......................................................................................................... 49 4.2. Temperature effects on rheological properties ............................................ 49 4.2.1. Method ............................................................................................................ 49 4.2.2. Results ............................................................................................................. 49 4.2.2.1. Melt curves .................................................................................................. 49 4.2.2.2. BSGC as function of temperature ................................................................ 54 4.3. Moisture effect on rheological properties ...................................................... 58 4.3.1. Cheese drying .................................................................................................. 58 4.3.2. Results of cheese drying ................................................................................. 59 4.3.3. Measurement of rheological properties of mozzarella ................................. 61 4.3.4. Rheological results .......................................................................................... 61 4.4. Conclusion ............................................................................................................. 63 5. ROTATIONAL RHEOLOGY METHOD DEVELOPMENT ...................................................... 65 5.1. Introduction .......................................................................................................... 65 5.1.1. Rotational rheometer ..................................................................................... 65 5.1.2. Sample preparation ........................................................................................ 68 5.1.3. Procedures for the parallel plate rheometer tests ........................................ 69 VI 5.2. Creep and recovery ............................................................................................. 70 5.2.1. High stress creep test ...................................................................................... 71 5.2.2. Results of the high stress creep test .............................................................. 71 5.2.3. Low stress creep and recovery test ................................................................ 74 5.2.4. Results of low stress creep and recovery test ............................................... 74 5.3. Controlled shear rate test .................................................................................. 76 5.3.1. Constant shear rate test ................................................................................. 76 5.3.2. Results of the constant shear rate test .......................................................... 77 5.3.3. Shear rate ramp test ....................................................................................... 78 5.3.4. Result of the shear rate ramp test ................................................................. 78 5.4. Oscillatory Rheometry ........................................................................................ 79 5.4.1. Method ............................................................................................................ 79 5.4.2. Results of the oscillatory test ......................................................................... 80 5.5. Conclusion ............................................................................................................. 81 6. ROTATIONAL VISCOMETER RESULTS ............................................................................. 83 6.1. Introduction .......................................................................................................... 83 6.2. Fibre direction effect in rotational rheometer .............................................. 83 6.2.1. Method ............................................................................................................ 83 6.2.2. Results ............................................................................................................. 83 6.3. Temperature effects on rheological properties ............................................ 85 6.3.1. Method ............................................................................................................ 85 6.3.2. Results ............................................................................................................. 85 6.4. Model development ............................................................................................. 87 6.4.1. Power law model fitting raw data .................................................................. 87 6.4.1.1. Model Fitting Method .................................................................................. 88 6.4.1.2. Results.......................................................................................................... 88 6.4.2. Arrhenius model fitting to consistency index ................................................ 90 6.4.2.1. Comparison between Model and Experimental Data.................................. 92 6.4.3. WLF model fitting to consistency index ......................................................... 93 6.4.3.1. Comparison between model and experimental data .................................. 94 VII 6.4.4. Comparison between two models ................................................................. 95 6.5. Moisture effect on rheological properties ...................................................... 96 6.5.1. Mozzarella cheese dried by salt solutions ..................................................... 96 6.5.2. Mozzarella cheese drying in a fridge ............................................................ 102 6.6. Comparison/explanation of the results from UW Meltmeter and rotational viscometry ................................................................................................... 104 6.7. Conclusion ........................................................................................................... 107 7. CONCLUSION ................................................................................................................. 108 7.1. Conclusion ........................................................................................................... 108 7.2. Recommendation ............................................................................................... 109 8. REFERENCES .................................................................................................................. 110 9. APPENDIX ...................................................................................................................... 116 9.1. Moisture content method (16 hour oven) .................................................... 116 9.2. Procedure summary of the model development ......................................... 118 VIII LIST OF TABLES Table 2 - 1 Conventional functional properties of melting cheese (adapted from Fox et al., 2000) . 5 Table 3 - 1 Weight of samples cut by two templates ...................................................................... 29 Table 3 - 2 The final height of samples ............................................................................................ 33 Table 3 - 3 The base temperature of cheese during testing ............................................................ 34 Table 3 - 4 Mean BSGC at 3 BESRs for two fibre direction sample at 30 °C .................................... 44 Table 3 - 5 Mean BSGC at 3 BESRs for two fibre direction sample at 45 °C .................................... 44 Table 3 - 6 Mean BSGC at 3 BESRs for two fibre direction sample at 60 °C .................................... 44 Table 4 - 1 Moisture content and water activity of mozzarella cheese ........................................... 60 Table 6- 1 The consistency index k and behaviour index n at the different temperatures ............. 89 Table 6- 2 The consistency index k regressed from the power law equation with a constant n=0.47 ........................................................................................................................................................ 90 Table 6- 3 Viscosity model parameters for mozzarella cheese as function of shear rate and temperature .................................................................................................................................... 92 Table 6- 4 WLF model parameters for mozzarella cheese as function of shear rate and temperature ........................................................................................................................................................ 94