GAS CELLS IN BREAD DOUGH A thesis submitted to The University of Manchester for the degree of Doctor of Philosophy in the School of Chemical Engineering and Analytical Science 2013 Linda Trinh School of Chemical Engineering and Analytical Science 1 Contents Contents ......................................................................................................2 List of Tables ................................................................................................5 List of Figures ...............................................................................................6 Nomenclature ............................................................................................. 12 Abbreviations ........................................................................................... 12 Notation ................................................................................................. 12 Abstract..................................................................................................... 14 Declaration ................................................................................................. 16 Copyright Statement ..................................................................................... 16 Acknowledgements ....................................................................................... 17 Chapter 1 - Introduction: Understanding bread dough aeration ..................................... 18 Chapter 2 - Bread: Its history, significance and manufacture ....................................... 23 2.1 An introduction to bread ........................................................................... 23 2.1.1 The significance of bread ..................................................................... 23 2.1.2 Industrial breadmaking - the Chorleywood Bread Process .............................. 25 2.1.3 Breadmaking ingredients ...................................................................... 27 2.2 Aeration throughout breadmaking ................................................................ 33 2.2.1 Entrainment and disentrainment of gas .................................................... 33 2.2.2 Parameters during mixing affecting cells in bread dough ............................... 36 2.2.3 Measuring aeration throughout breadmaking .............................................. 39 2.2.4 Quantifying aeration using a population balance model ................................ 45 2.3 Summary of bread’s history, significance and manufacture ................................. 48 Chapter 3 - Experimental methodologies ................................................................ 49 3.1 Outline ................................................................................................. 49 3.2 Materials used ........................................................................................ 49 3.3 Equipment used ...................................................................................... 50 3.3.1 Tweedy 1 mixer ................................................................................. 52 3.3.2 Nikon Metris 225/320kV X-ray CT ............................................................ 54 3.3.3 Farinograph ...................................................................................... 56 3.3.4 Micro-Dough lab ................................................................................. 56 3.3.5 C-Cell ............................................................................................. 56 3.3.6 Texture Analyser ................................................................................ 57 3.4 Analytical techniques used ......................................................................... 58 3.4.1 Determining flour water absorption in the Farinograph ................................. 58 3.4.2 Determining flour water absorption on the Micro-Dough Lab .......................... 58 3.4.3 Measuring dough density ...................................................................... 58 3.4.4 Determining the gas free dough density .................................................... 60 3.4.5 Determining dough voidage ................................................................... 60 2 3.4.6 Specific volume and density of bread ....................................................... 61 3.5 Flour and dough characterisation ................................................................. 61 3.5.1 Flour water absorption ........................................................................ 61 3.5.2 Mixing at constant pressure: gas free dough density ..................................... 63 3.5.3 Dough voidage ................................................................................... 64 3.5.4 Characterisation summary .................................................................... 64 3.6 Additional methodologies ........................................................................... 65 3.6.1 Breadmaking ..................................................................................... 65 3.6.2 X-ray imaging .................................................................................... 65 Chapter 4 - Assessment of the effect of sugar on dough properties during breadmaking processes ...................................................................................................... 67 4.1 Introduction ........................................................................................... 67 4.2 Interaction of sugar and starch-water mixture ................................................. 67 4.2.1 Method: Interaction of sugar and starch-water mixture ................................. 68 4.2.1 Results and discussion: Interaction of sugar and starch-water mixture .............. 68 4.3 Gas free dough density and voidage of different sugar content doughs ................... 70 4.3.1 Method: Gas free dough density and voidage of different sugar content doughs ... 70 4.3.2 Results: Gas free dough density and voidage of different sugar content doughs ... 71 4.4 Mixing different sugar content doughs in the Farinograph ................................... 74 4.4.1 Method: Mixing different sugar content doughs in the Farinograph ................... 74 4.4.2 Results and discussion: Mixing different sugar content doughs in the Farinograph 76 4.5 The effect of sugar on torque during mixing .................................................... 80 4.5.1 Method: The effect of sugar on torque during mixing ................................... 81 4.5.2 Results and discussion: The effect of sugar on torque during mixing ................. 83 4.6 The effect of mixing speed on aeration of sugared doughs .................................. 86 4.6.1 Method: The effect of mixing speed on aeration of sugared doughs .................. 86 4.6.2 Results and discussion: The effect of mixing speed on aeration of sugared doughs 86 4.7 The effect of sugar on dough stickiness.......................................................... 87 4.7.1 Method: The effect of sugar on dough stickiness ......................................... 87 4.7.2 Results and discussion: The effect of sugar on dough stickiness ....................... 89 4.8 The effect of sugar on dough uniaxial extension ............................................... 91 4.8.1 Method: The effect of sugar on dough uniaxial extension .............................. 91 4.8.2 Results and discussion: The effect of sugar on dough uniaxial extension ............ 94 4.9 ESEM of different sugar content doughs ......................................................... 98 4.9.1 Method: ESEM of different sugar content doughs ......................................... 98 4.9.2 Results and discussion: ESEM of different sugar content doughs ...................... 99 4.10 The effect of sugar on the dynamic dough density during proving ....................... 102 4.10.1 Method: The effect of sugar on the dynamic dough density during proving ....... 102 4.10.2 Results and discussion: The effect of sugar on the dynamic dough density during proving .................................................................................................. 103 3 4.11 The effect of sugar on finished bread ......................................................... 107 4.11.1 Method: The effect of sugar on finished bread ......................................... 107 4.11.2 Results and discussion: The effect of sugar on finished bread ....................... 109 4.12 Summary ............................................................................................ 124 Chapter 5 - Aeration in bread dough with and without sugar ....................................... 126 5.1 Introduction .......................................................................................... 126 5.2 Aeration of bread dough with and without sugar methodology ............................. 126 5.2.1 Experimental methodology .................................................................. 127 5.2.2 Pressure step change modelling methodology ........................................... 129 5.3 Results and discussion .............................................................................. 129 5.3.1 Experimental results .......................................................................... 130 5.3.2 Pressure step change modelling results ................................................... 140 5.4 Summary .............................................................................................. 143 Chapter 6 -