1 Mixing in the food industry: trends and challenges
1.1 Role of mixing
1.2 Design criteria for mixing
1.3 Specific challenges in food mixing
1.3.1 Quality assurance compliance through mixing
1.3.2 Engineering texture through mixing
1.4 Advances in the science of mixing
1.5 Book objectives
2 Mixing fundamentals
2.1 Introduction
2.2 Defining mixing
2.2.1 Macromixing
2.2.2 Mesomixing
2.2.3 Micromixing
1 Mixing in the food industry: trends and challenges
1.1 Role of mixing
1.2 Design criteria for mixing
1.3 Specific challenges in food mixing
1.3.1 Quality assurance compliance through mixing
1.3.2 Engineering texture through mixing
1.4 Advances in the science of mixing
1.5 Book objectives
2 Mixing fundamentals
2.1 Introduction
2.2 Defining mixing
2.2.1 Macromixing
2.2.2 Mesomixing
2.2.3 Micromixing
2.3 Scale of scrutiny
2.4 Quantifying mixedness
2.4.1 Inference of mixing indices
2.5 Determining the end point of mixing
2.5.1 Solids mixing
2.5.2 Fluid mixing
2.5.3 MuIti-phase mixing
2.5.4 Alternative measures of mixedness in industrial practice
2.6 Residence time distributions
2.6.1 Modelling of residence time distributions
3 Kinematics of flow and mixing mechanisms
3.1 Introduction
3.2 Fluid mixing
3.2.1 Kinematics of fluid flow
3.2.2 Quantification of flow regimes
3.2.3 Chaotic advection
3.2.4 Fluid mixing mechanisms
3.3 Solids mixing
3.3.1 Mixing flow in solids
3.3.2 Solids mixing mechanism
3.4 Identification of mixing mechanisms
3.4.1 Solids
3.4.2 Fluids
4 Rheology and mixing
4.1 Introduction
4.2 Dispersion rheology
4.2.1 Forces acting on dispersed particles
4.2.2 Parameters affecting suspension rheology
4.3 Fluid rheology and mixing
4.3.1 Shear flow
4.3.2 Elongational flow
4.4 Effects of mixing on fluid rheology
4.5 Mixer rheometry
4.5.1 Theory
4.5.2 Mixer rheometry applications
4.6 Conclusion
5 Equipment design
5.1 Introduction
5.2 Liquid mixing equipment
5.2.1 Portable mixers
5.2.2 General purpose liquid mixers
5.2.3 Mixer shafts design
5.2.4 Other mechanical design considerations
5.2.5 Special purpose liquid mixing equipment
5.2.6 Food specific mixing equipment
5.3 Powder mixing equipment
5.3.1 Ribbon blenders
5.3.2 Paddle blenders
5.3.3 Combination blenders
5.3.4 Tumble blenders
5.3.5 Loading and emptying blenders
5.3.6 Liquid addition to powders
5.3.7 Sampling
5.3.8 Safety
5.3.9 Blending systems
5.4 Equipment components
5.4.1 Electric motors
5.4.2 Speed reducers
5.4.3 Seals
6 Mixing scale-up
6.1 Introduction
6.2 Scale-up for fluid mixing
6.2.1 Dimensional analysis
6.2.2 Scale-up with geometric similarity
6.2.3 Scale-up without geometric similarity
6.3 Scale-up for powder mixing
7 Monitoring and control of mixing operations
7.1 Introduction
7.2 Torque and power measurement
7.3 Flow measurement
7.3.1 Hot-wire anemometry
7.3.2 Laser Doppler anemometry
7.3.3 Phase Doppler anemometry
7.3.4 Flow visualization using computer vision
7.3.5 Particle image velocimetry
7.3.6 Planar laser-induced fluorescence
7.3.7 Tomography
7.4 Quantification of mixing time
7.4.1 NIR spectroscopy
7.4.2 Chemical imaging
8 Computational fluid mixing
8.1 Introduction
8.1.1 History of CFD
8.1.2 Steps towards CFD simulation of mixing processes
8.2 Conservation equations
8.2.1 Mass conservation
8.2.2 Momentum conservation
8.2.3 Turbulence
8.2.4 Energy conservation
8.2.5 Species transport
8.2.6 Turbulent species and energy transport
8.2.7 Boundary conditions
8.3 Numerical methods
8.3.1 Discretised solution of the flow variables
8.3.2 Grid generation
8.3.3 Discretisation
8.3.4 Finite-volume discretisation methods
8.3.5 Solver methods
8.4 Application of CFD to stirred tank modelling
8.4.1 Mixing operations
8.4.2 Representation of the impeller
8.4.3 Prediction of mixer performance characteristics
8.4.4 Simulation of unbaffled or partially baffled stirred tanks
8.4.5 Simulation of single-phase flow in baffled stirred tanks
8.4.6 Mixing and blending simulations
8.4.7 MuIti-phase simulations
8.5 Application to food mixing operations
8.5.1 Challenges for simulation of food processes
8.5.2 Examples of food applications
8.6 Closing remarks
9 Immiscible liquid-liquid mixing
9.1 Introduction
9.2 Emulsion types and properties
9.2.1 Kinetically trapped nano-emulsions
9.2.2 Pickering emulsions
9.2.3 Double emulsions
9.2.4 Air-filled emulsions
9.2.5 Water-in-water emulsions
9.3 Future challenges
9.3.1 Better mechanistic understanding of the emulsification process(es)
9.3.2 Improved emulsification processes
9.3.3 Designed emulsions for improved nutrition and heaIth
9.3.4 Reduced use of surfactants for environmental reasons
10 Solid-liquid mixing
10.1 Introduction
10.2 Regimes of solids suspension and distribution
10.2.1 State of nearly complete suspension with filleting
10.2.2 State of complete particle motion
10.2.3 State of complete off-bottom suspension
10.2.4 State of homogeneous or uniform suspension
10.3 Prediction of minimum speed for complete suspension
10.3.1 Influence of physical properties
10.3.2 Influence of solids concentration
10.3.3 Influence of geometric parameters
10.4 Hydrodynamics of particle suspension and distribution
10.4.1 Particle slip velocity
10.4.2 Particle settling and drag
10.5 Scale-up of solid-liquid mixing
10.6 Damage to food particles in suspension
10.7 Fine particle slurries
11 Gas-liquid mixing
11.1 Introduction
11.2 Gas-liquid dispersion operations
11.2.1 Characteristics of dispersed phase-mean diameter
11.2.2 Gas dispersion-bubble behaviour
11.2.3 Gas dispersion in agitated vessels
11.3 Power input to turbine dispersers
11.4 Gas handling capacity and loading of turbine impeller
11.5 Bubbles in foods
11.6 Methods for mixing gas in liquid
11.6.1 Mixing by mechanical agitation under positive pressure
11.6.2 Mixing by mechanical agitation under vacuum
11.6.3 Steam-induced mixing
11.6.4 Other gas-liquid mixing methods
11.7 Characterization of bubble-containing structures
11.7.1 Gashold-up
11.7.2 Bubble size distribution
11.7.3 Rheological characterization
11.8 Role of gases and specifie ingredients in characterizing interfacial and rheological properties
11.9 Stability of foams and solidification of bubbly dispersions
11.10 Ultrasound in gas mixing and applications in food aeration
12 Evaluation of mixing and air bubble dispersion in viscous liquids using numerical simulations
12.1 Introduction
12.2 Measures of mixing and evaluation of flow
12.2.1 Efficiency of stretching
12.2.2 Dispersive mixing efficiency
12.2.3 Distributive mixing efficiency
12.3 Governing equations for calculation of flow
12.4 CFD approaches for simulation of mixing flows
12.4.1 Finite element method
12.4.2 Techniques to handle moving parts
12.5 FEM numerical simulation of batch mixer geometries
12.5.1 3D numerical simulation of flow in a Brabender Farinograph@
12.5.2 Analysis of mixing in 2D single-screw and twin-screw geometries
12.6 3D Numerical simulation of twin-screw continuous mixer geometries
12.6.1 Distributive mixing efficiency in a 3D mixing geometry
12.6.2 Evaluation of dispersive mixing in 3D continuous mixer geometry
12.7 Prediction of bubble and drop dispersion in a continuous mixer
12.8 Summary
13 Particulate and powder mixing
13.1 Introduction
13.2 Characterisation of particulate mixtures
13.2.1 Types of mixtures
13.2.2 Mixture quality
13.3 Assessment of mixture quality
13.3.1 Sampling
13.3.2 Sample variance and standard deviation
13.3.3 Lacey and Poole indices of mixture quality
13.3.4 Relative standard deviation
13.3.5 Estimating the true variance (delta2) from the random sample variance (S2)
13.3.6 Assessing if satisfactory mixture quality is achieved
13.3.7 'Baking a cake' method of assessing mixture quality
13.3.8 Influence of particle size and powder cohesiveness on mixture quality
13.4 Mixing mechanisms
13.4.1 Convection or macromixing
13.4.2 Diffusion or micromixing
13.4.3 Shearing
13.5 Segregation or demixing
13.5.1 Segregation
13.5.2 Reducing segregation
13.6 Powder mixing equipment
13.6.1 Tumbling mixers
13.6.2 Convective mixers
13.6.3 High shear mixers
13.6.4 Sigma blade mixers
13.6.5 Continuous mixers
13.7 Mixer selection and process design
13.7.1 Specification of mixture quality requirement
13.7.2 Mixer selection
13.7.3 Process design
13.8 Other factors affecting mixing process design in dry food processing
13.8.1 Hygiene and cleaning
13.8.2 Addition of multiple ingredients with large variation in properties
13.8.3 Addition of ingredients in liquid form
13.8.4 Dust prevention and control
Index
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