Practical Food Rheology
An Interpretive Approach

Rheology is fundamentally important in food manufacturing in two major senses. Understanding the way in which a substance moves and behaves is essential in order to be able to transport and mix it during processing. Secondly, the rheology of a product dictates much of the consumer experience, e.g. in relation to texture and mouthfeel.

This book doesn?t overwhelm the reader with complex mathematical equations but takes a simple and practically-focused approach, interpreting the implications of rheological data for use in different food systems. Through this approach industry-based food developers / rheologists, students, and academics are given clear, concise interpretation of rheological data which directly relates to actual perceived functionality in the food. The functionality may relate to texture, structure and mouthfeel, and may result as a function of temperature, pH, flocculation, concentration effects, and mixing.

The interpretative view is based on the principle that the food rheologist will produce a graph, for example of viscosity or gelation profiling, and then have to extract a practical meaning from it. For example, if viscosity falls with time as a function of pH, this knowledge can be used to tell the customer that the viscosity can be followed with just a pH meter and a stopwatch.  Rheological measurements have shown that once the pH has dropped 1 unit after 10 minutes, the viscosity has been halved. This is the type of practical and valuable information for customers of the industrial food rheologist which the book will enable readers to access. 

Key features:

• A uniquely practical approach to the often difficult science of food rheology
• Includes chapters introducing the basics of food rheology before moving on to how data can be usefully and easily interpreted by the food scientist
• Can be used as a teaching aid on academic or industry-based courses 

Preface.

Contributors.

1 Introduction – Why the Interpretive Approach? (Niall W. G. Young).

1.1 Rheology – What is in it for me?

1.1.1 Case study.

2 Viscosity and Oscillatory Rheology (Taghi Miri).

2.1 Introduction.

2.2 Food rheology.

2.3 Directions of rheological research.

2.3.1 Phenomenological rheology or macrorheology.

2.3.2 Structural rheology or microrheology.

2.3.3 Rheometry.

2.3.4 Applied rheology.

2.4 Steady-state shear flow behaviour: viscosity.

2.4.1 Rheological models for shear flow.

2.4.2 Wall slip.

2.5 Viscoelasticity and oscillation.

2.5.1 Oscillatory testing.

2.6 Process, rheology and microstructural interactions.

2.7 Rheology of soft solids.

2.7.1 Capillary rheometer.

2.7.2 Squeeze flow rheometer.

2.8 Measuring instruments – practical aspects.

2.8.1 Choosing the right measuring system.

3 Doppler Ultrasound-Based Rheology (Beat Birkhofer).

3.1 Introduction.

3.1.1 Overview.

3.1.2 History of ultrasonic velocimetry.

3.1.3 Existing literature on UVP-based rheometry.

3.2 Ultrasound transducers.

3.3 Flow adapter.

3.3.1 Doppler angle.

3.4 Acoustic properties.

3.4.1 Propagation.

3.4.2 Attenuation.

3.4.3 Sound velocity.

3.4.4 Scattering.

3.4.5 Backscattering.

3.5 Electronics, signal processing and software.

3.5.1 Electronics.

3.5.2 Signal processing and profile estimation.

3.5.3 Software.

3.6 Pipe flow and fluid models.

3.6.1 Gradient method or point-wise rheological characterisation.

3.6.2 Power law fluid model.

3.6.3 Herschel–Bulkley fluid model.

3.6.4 Other models.

3.7 Rheometry.

3.7.1 Averaging effects at the pipe wall.

3.7.2 Fitting.

3.7.3 Gradient method.

3.8 Examples.

3.8.1 Carbopol solution.

3.8.2 Suspension of polyamide in rapeseed oil.

3.9 Summary.

4 Hydrocolloid Gums – Their Role and Interactions in Foods (Tim Foster and Bettina Wolf).

4.1 Introduction.

4.2 Behaviour of hydrocolloid gums in solution.

4.3 Hydrocolloid gelation and gel rheology.

4.4 Hydrocolloid–hydrocolloid interactions.

4.5 Hydrocolloids in foods – role and interactions.

5 Xanthan Gum – Functionality and Application (Graham Sworn).

5.1 Introduction.

5.2 Xanthan molecular structure and its influence on functionality.

5.3 The conformational states of xanthan gum.

5.4 Food ingredients and their effects on xanthan gum functionality.

5.4.1 Salts.

5.4.2 Acids (pH).

5.4.3 Xanthan and proteins.

5.4.4 Xanthan and starch.

5.5 Food processing and its impact on xanthan gum functionality.

5.5.1 Thermal treatment.

5.5.2 Homogenisation.

5.5.3 Freezing.

5.6 Food structures.

5.6.1 Emulsions.

5.6.2 Gels.

5.7 Applications.

5.8 Future trends.

6 Alginates in Foods (Alan M. Smith and Taghi Miri).

6.1 Alginate source and molecular structure.

6.2 Alginate hydrogels.

6.3 Alginic acid.

6.4 Alginate solutions.

6.5 Enzymatically tailored alginate.

6.6 Alginates as food additive.

6.6.1 Gelling agent.

6.6.2 Thickening agent.

6.6.3 Film-forming agent.

6.6.4 Encapsulation and immobilisation.

6.6.5 Texturisation of vegetative materials.

6.6.6 Stabiliser.

6.6.7 Appetite control.

6.6.8 Summary.

7 Dairy Systems (E. Allen Foegeding, Bongkosh Vardhanabhuti and Xin Yang).

7.1 Introduction.

7.2 Fluid milk.

7.2.1 Rheological properties of milk.

7.2.2 Measurements of the rheological properties of milk.

7.2.3 Factors influencing milk rheological properties.

7.2.4 Correlating rheological properties of milk to sensory perceptions.

7.2.5 Process engineering calculation.

7.3 Solid cheese.

7.3.1 Small amplitude oscillatory tests.

7.3.2 Large strain rheological analysis.

7.3.3 Creep and stress relaxation.

7.4 Rheological properties of semi-solid dairy foods.

7.4.1 Flow properties.

7.4.2 Yield stress.

7.4.3 Viscoelastic properties of semi-solid dairy products.

7.5 Effect of oral processing on interpretation of rheological measurement.

8 Relationship between Food Rheology and Perception (John R. Mitchell and Bettina Wolf).

8.1 Introduction.

8.2 Rheology and thickness perception.

8.3 Rheology and flavour perception.

8.4 Mixing, microstructure, gels and mouthfeel.

8.4.1 Mixing.

8.4.2 Microstructure.

8.4.3 Mouthfeel.

8.4.4 Gels.

8.5 Beyond shear rheology.

8.6 Conclusions.

9 Protein-Stabilised Emulsions and Rheological Aspects of Structure and Mouthfeel (Fotios Spyropoulos, Ernest Alexander K. Heuer, Tom B. Mills and Serafim Bakalis).

9.1 Introduction.

9.2 Processing and stability of emulsions.

9.2.1 Instabilities in emulsions.

9.2.2 Protein functionality at liquid interfaces.

9.2.3 Protein-stabilised oil-in-water emulsions – Effect of aqueous phase composition.

9.2.4 Effect of processing.

9.3 Oral processes.

9.3.1 Different stages and phenomena during oral processing.

9.3.2 Fluid dynamics during oral processing.

9.3.3 Interactions with saliva.

9.3.4 Interaction with oral surfaces.

9.4 In vitro measurements of sensory perception.

9.5 Future perspectives.

10 Rheological Control and Understanding Necessary to Formulate Healthy Everyday Foods (Ian T. Norton, Abigail B. Norton, Fotios Spyropoulos, Benjamin J. D. Le Reverend and Philip Cox).

10.1 Introduction.

10.2 Design and control of material properties of foods inside people.

10.2.1 Oral perception of foods.

10.2.2 Food in the stomach.

10.2.3 Food in the intestine.

10.3 Reconstructing foods to be healthy and control dietary intake.

10.3.1 Use of emulsions as partial fat replacement.

10.3.2 Duplex emulsions.

10.3.3 Fat replacement with air-filled emulsion.

10.3.4 Sheared gels (fluid gels).

10.3.5 Water-in-water emulsions.

10.3.6 Self-structuring systems.

10.4 Conclusions.

References.

Index.

Professor Ian T Norton, Dr Fotios Spyropoulos and Dr Philip Cox, all of Chemical Engineering, University of Birmingham, Edgbaston, Birmingham, UK.