7/29/2019 Rheology of Food Materials

1/5

Rheology of food materials

Peter Fischer , Erich J. Windhab

Institute of Food, Nutrition and Health, ETH Zurich, 8092 Zurich, Switzerland

a b s t r a c ta r t i c l e i n f o

Article history:

Received 12 July 2010

Accepted 13 July 2010

Available online 18 July 2010

Keywords:

Rheology

Suspensions

Emulsions

Foams

Microstructure

Flow geometries

Tribology

Squeeze flow

Interfacial rheology

Soft glasses

Food rheology focuses on the flow properties of individual food components, which might already exhibit a

complex rheological response function, the flow of a composite food matrix, and the influence of processing

on the food structure and its properties. For processed food the composition and the addition of ingredients

to obtain a certain food quality and product performance requires profound rheological understanding ofindividual ingredients their relation to food processing, and their final perception.

2010 Elsevier Ltd. All rights reserved.

1. Introduction

Global challenges in food science are the sustainable and safe access

to clean water and supply of sufficient energy sources, i.e. food based on

fats, proteins, and carbohydrates for high quality human nutrition. In

this context food quality is mostly defined by sensorial characteristics

and consumer-driven preferences selecting the convenience level as

well as health supporting properties of the chosen food. Depending on

the socio-economical and nutritional background of the consumer,

individual diets might be different but will be, in particular in the so-

called Western Diet, based on food products thatare partially or entirely

processed.The resulting decomposition and subsequent re-composition

of food materials allows us to design food according to nutritional

guidelines and to add ingredients for enhancing the nutritional benefits

of the final product (e.g. fortification with micronutrients). The newly

tailored or designed food might be stabilized by thesame mechanismas

the original food components, but removed or added components will

need additional stabilizing methods. It is not surprising that along with

the emergence of processed foods, food science has devoted significant

research to the role of individual ingredients, in particular to stabilizing

agents. Journals focusing on food hydrocolloids, carbohydrate biopoly-

mers, or food hydrocarbons and on interactions of ingredients with the

food matrix were established in the 1980 s, while research on non-

composed food such as starch-based products nucleated journals

already in the early 1950 s. Food processing heavily relies on complex

flow processes. Therefore, rheological characterization of the individualingredients as well as thecomposedfood product found on supermarket

shelves is an integral part of food science. Rheological research in food

science is therefore closely linked to the development of food products

and could address the industrial production of food (stirring, pumping,

dosing, dispersing, spraying), home based cooking as well as consump-

tion of food (oral perception, digestion, well-being).

Properties of processed food products are increasingly tailored to

meet consumers' requirements and benefits. Tailored product

properties are designed along structureproperty and process

structure guidelines, considering structure from the molecular to

the macroscopic scales and its consequences on processing and

perception. Rheology comes into play in the context of structure as

one of its most prominent dynamic properties. The close link of

rheology and structure also introduces the relationship to flow

processing, which determines the dynamic conditions under which

the food material flows. Particularly for food systems rheology plays

an important role because (i) flow properties define food structure

during manufacturing (factory) or preparation (kitchen) and (ii)

physiologically in mouth, stomach, and intestinewhere food structure

is perceived and digested. Rheology impacts directly on perception

and digestion by influencing the flow characteristics during mastica-

tion and digestion but also triggers other quality characteristics such

as flavor or nutrient release at specific sites.

Food rheology is not an unified discipline, but its practice can be

subdivided into three categories. A first category is represented by

food product developers mostly based on a food technology

Current Opinion in Colloid & Interface Science 16 (2011) 3640

Corresponding author.

E-mail address: peter.fischer@ilw.agrl.ethz.ch (P. Fischer).

1359-0294/$ see front matter 2010 Elsevier Ltd. All rights reserved.

doi:10.1016/j.cocis.2010.07.003

Contents lists available at ScienceDirect

Current Opinion in Colloid & Interface Science

j o u r n a l h o m e p a g e : w w w. e l s ev i e r. c o m / l o c a t e / c o c i s

http://dx.doi.org/10.1016/j.cocis.2010.07.003http://dx.doi.org/10.1016/j.cocis.2010.07.003http://dx.doi.org/10.1016/j.cocis.2010.07.003mailto:peter.fischer@ilw.agrl.ethz.chmailto:peter.fischer@ilw.agrl.ethz.chmailto:peter.fischer@ilw.agrl.ethz.chhttp://dx.doi.org/10.1016/j.cocis.2010.07.003http://www.sciencedirect.com/science/journal/13590294http://www.sciencedirect.com/science/journal/13590294http://dx.doi.org/10.1016/j.cocis.2010.07.003mailto:peter.fischer@ilw.agrl.ethz.chhttp://dx.doi.org/10.1016/j.cocis.2010.07.003

7/29/2019 Rheology of Food Materials

2/5

background and aimed at comparative characterization of food

products and rheologyproperty relationships. Typical properties of

interest correlated with rheology are (i) sensory / perception

characteristics (e.g. texture), (ii) stability, (iii) convenience aspects

(e.g. portioning, scoping, dosing, filling) and (iv) nutritive character-

istics (e.g. release kinetics, satiety). The second category are

represented by food engineers, who try to develop rheologyprocess

relationships of the food and use rheological data for process or

product optimization. Rheological measurements are also used inanalytical to semi-empirical modelling as well as in numerical flow

process simulations. Typicalflow processes in food processing include

mixing/stirring, dispersing, extrusion, spinning, coating, injection

moulding and spraying. The third category is represented by material

scientists or physicists who focus on rheologystructure relationships

of soft materials. They are mostly interested in model food systems,

rheometric model flows as well as analytical to semi-empirical

modelling and simulations.

In a recent review we have attempted to give a brief overview of

current food rheology based on structural criteria, including phenom-

enological, processing-related and molecularly-based approaches [1].

Here, this brief overview intends to shed some light on rheological

techniques as well as on some recentresearchtrends in food rheology.

2. Dealing with a hierarchical material

Food products maybe simpleliquids or solidsbut thevast majority

of food materials belong to the category of soft condensed matter

composed of a range of hierarchical nanostructures and microstruc-

tures [28]. Accordingly, suspension, emulsion and interfaces [914],

foams [1520], biopolymer gels and mixtures [2127] can be the food

encountered in rheological investigations. The rheology of such

complex products is governed by the main ingredients and their

interactions on a wide variety of length and time scales. For example,

droplets and particles in a typical food emulsion or food suspension,

e.g. in a salad dressing andor in chocolate, areprimarily interacting on

the non-colloidal level, whereas the proteins, surfactants, cell walls,

lipids, polysaccharides stabilizing the dispersed system interact on the

colloidal length scale. Moreover, in industrial scale food processinglength scales in order of meters are relevant. The corresponding time

scales maybe in the sub-millisecond regime duringaggregation of the

ingredients or up to years during the long-term shelf life of canned

food products [6,12,13,24,2836].

The aim of rheological characterization is to quantify the

functional relationships between deformation, stresses, and the

resulting rheological properties such as viscosity, elasticity, or

viscoelasticity. A prerequisite for proper rheological data is rheo-

metric flow conditions, i.e. a defined laminar deformation field.

Considering strawberry yoghurt or any other heterogeneously

structured material it is clear that for many food products classical

rheological devices will fail due to non-homogeneous flow fields. As a

consequence, partly strange measuring devices for food characteriza-

tion were developedin thepast simply because themeasurements aremotivated by quick and reliable evaluation during food processing or

by the fact that, literally spoken, a whole apple does not fit into a

Couette geometry and even if it would, the resulting flow profile

would most likely not be rheometrical in the strictest sense. For

practical purposes, the latter example can be avoided by using

different mechanical analysis techniques to tackle the hierarchical

structure of food systems such as fruits, cheese, dough, meat beside

others. On the other hand, rheological experiments on individual

ingredients in aqueous or lipid-based solvents neglect the complexity

of thereal food matrixbut provide understanding of the self-assembly

of food ingredients on the colloidal level. Considering the mentioned

approaches it becomes clear that food rheology is defined by its

application rather than by a straightforward physical classification of

materials.

2.1. Rheology and human perception

During mastication and swallowing the tongue and mouth senses

only those aggregates greater than 20 m [33]. Structured food

products either benefit from this size limit (structure breakdown is

associated with textural sensation and is coupled with flavor and

nutrient release and therefore clearly links to eating pleasure) or

should be avoided (sandy mouth feel in chocolate is associated with a

insuffi

ciently refi

ned product). Since many food systems, e.g. emul-sions and food suspensions, do have aggregate sizes of several m,

food manufacturing operations aim at changing the microstructure on

this length-scale. In classical food technology and food engineering it

is therefore of main interest to control the final food structure and its

perception and texture [3745]. For food quality control, relating

textural perception to physical measurements of food structure, such

as rheological properties, requires understanding of the breakdown

pathway of food during mastication and the correlation of instru-

mental readings to decisions taken by humans. In this framework,

biopolymer gels are considered as a suitable model systems to link

food structure and texture to rheological properties [40] because the

gelation mechanism of biopolymers composed out of proteins,

polysaccharides and combinations thereof is considerably known so

that samples meet the requirements for parameter variations in a

sensorial test. The limited capacities of any rheological technique

(including rheometers, viscometers, texture analyzers, and consist-

ometers) to elucidate texture and perception requires additional

descriptions of the product. To close this gap, combinations of sensory

evaluation and structure analysis utilizing fluorescence microscopy,

confocal laser scanning microscopy, NMR, and numerical modeling

are use in order to characterize both microstructure and fracture

evolution during mastication [4649]. It is to be expected that in the

future combined approaches measuring food structure, rheological

properties, oral processing, and sensory properties will addressed the

topic in detail.

A phenomena linked to perception and food structure is the recent

society-driven trend in food science for the replacement or the

reduction of fat. In case of a prominent candidate of a non-colloidal

food material, chocolate, this would be the creation of low calorieproduct with thesame perceived properties as the full fat original. The

easiest way to achieve this goal is the reduction of the cocoa and milk

fatbut this would lead to an increase of thechocolate viscositycausing

problems during manufacturing [33]. Rheological characterization of

the flow properties as well as modifications of the ingredients are

required to optimize the chocolate suspension. In the first case, the

particle size distributionand theparticleshapecan be adapted to keep

the chocolate melt viscosity acceptable for processing [33,5053]

while for the later case addition of biopolymer gels or oils has been

proposed [23,54]. In both cases, rheological investigations support the

optimization the final food product by helping to understand the role

of other relevant ingredients, i.e. oil and fat as matrix fluid, cocoa,

sugar, and milk powder as dispersed materials. In addition, phospho-

lipids such as lecithin used in chocolate have significant impact on therheological properties. This indicates that the interaction of the

dispersed particles can be controlled by the surface coating with self-

assembled colloidal compounds.

2.2. Complex flow phenomena in multiscale food systems

Beside the non-trivial link between instrumental readings provid-

ed by rheometers and human perception of food, the rheological

response of complex food materials can be challenging by its own.

One inherent problem of concentrated and structured food materials

is the occurrence of yielding: an apparent solid-to-liquid flow

transition is observed, depending on the material structure and the

applied shear stress. Examples can be found in food products such as

ketchup, sauces, mayonnaise, yogurt, margarine and in many other

37P. Fischer, E.J. Windhab / Current Opinion in Colloid & Interface Science 16 (2011) 3640

7/29/2019 Rheology of Food Materials

3/5

systems [7,5557]. Yielding phenomena and yield stresses have

received considerable attention over the last decades and we will

not repeat the discussion in full detail. However, it is safe to say that

for hierarchical food materials showing a solid-like behavior at rest

the internal nano- and microstructure resists the applied stress and

reversibly deforms. Structural breakdown will lead to both a structure

different to the original one and to flow. The stress necessary to

initiate a flow transition is called yield stress and distinguishes elastic

deformation and viscous or viscoelasticfl

ow. It is important to keep inmind that thematerial will retain its chemical composition, but canbe

present in very distinct structures. For example, a classical semi-solid

yoghurt exhibits elastic response best tested with a vane geometry in

its original container, or using small amplitude oscillatory shear

deformation if adequate sample preparation is possible, whereas

yoghurt under shear shows a viscous response and can be tested in

more traditional rheometrical geometries.

There is always interaction between the applied flow field, the

measuring device, the measuring conditions and, of course, the

sample material. In classical rheometric geometries (plate/plate,

concentric cylinders), proper choice of the surface topography of the

shearing surfaces is important [58]. Additionally, to minimize the

effect of yielding and slip, several specialized rheometrical devices

have been proposed in the past. All those geometries aim to reduce

thesurface area where slippage occurs, jeopardize a well-definedflow

field by doing so. Commercial viscosimeter geometries, helical ribbon

and pin mixers, ball measuring systems as well as vane geometries

[5962] are widely used. Amongall, the vane is probably the one for

which the most solid fluid mechanical analysis is available, i.e. the

one that is closest to a rheometric flow [60,6365]. It should be kept

in mind that all geometries provide not shear rate and shear stress,

but torque and rotational speed. To obtain rheological data, a mixer

analysis using model fluids showing similar flow properties as the

unknown sample (e.g. yielding,power law behavior,thixotropy) must

be performed prior any analysis [62]. For heterogeneous materials

such as strawberry yoghurt the mentioned geometries might be the

only chance to obtain rheological data at all. Faced with no data or

relative data with errors; using a mixer geometry means opting for

the latter one, ideally keeping in mind that no absolute values can beobtained. Beside the mentionedflow geometries adapted to rotational

rheometers, in-line rheometry can be used to obtain process-related

rheological data. In recent years non-invasive inline methods such as

resonator-based and ultrasonic-Doppler based devices have been

proposed and utilized for the characterization of fat crystal suspen-

sions, salad dressings, chocolate, and cheese [66,67].

Associated with the complex flow field for yielding materials as

well with the perception of food and break down of food structure

during mastication, squeeze flow and lubrication flow offer flow fields

that have been claimed to be close to the flow in the mouth. The use of

squeezeflow rheometry to overcome yielding and slippage as well as

special squeeze flow devices such as inverted filament stretching set-

ups to study bi-axial elongational flow have been discussed recently

[6871]. It is important to memorize that while squeezing flowbetween a pair of parallel discs or a plate and a sphere seems to be a

simple experiment, the choice of the appropriate model, data analysis

and boundary conditions (slip or no slip, rough or smooth surface, ...)

is extremely importantand the wrong choice can easily ruin entireset

of experiments.

Another application of squeeze flow is seen in dough rheology

where both tradition and a complex viscoelastic sample complicate

the use of standard shear rheological investigations. Dough can be

seen as a starch particle suspension dispersed in a concentrated

biopolymer solution where interactions on the molecular to the

micron length scale determine the overall rheological properties,

baking process, and final bread quality. In dough rheology the strong

link to bread-making and the instantaneous measurement of dough

quality prior the bread baking rationalized special characterization

methods [7277]. A considerable amount of publications address the

characterization of the expandingbubble technique (biaxial extension

flow) and its numerical simulation [7881]. Dough rheology is a good

example of an industrial-based characterization method with strong

standing in food rheology; it cannot be easily replaced, even though it

might be hampered by non-ideal flow properties. Approaches that

aim to introduce extensional rheometry [8286] are extremely useful

to understand the material but are complicated by the fact that

measuring devices are expensive, do not operate in the productiontime scale, and do not provide instrumental readings easily be

transferred to the process or to the baker at four o'clock in the

morning.

Tribology, lubrication, triborheometry, and micro-gap rheometry

has recently received considerable attention to study the effect of

shear, squeeze flow and the role of confinement at length scales that

are approaching the length scale of the food microstructure [8790].

For example, the lubricating properties of human saliva is influenced

by health and diet conditions but also depends on the food material it

interacts with [9194]. Saliva lubricates and protects surfaces in the

mouth, supports transport of food materials and aids in taste

perception. Using tribological methods to study the situation in the

mouth it was found that saliva, depending on the food eaten, exhibits

a very high elasticity for a generally low viscous fluid. As explanation

it is rationalized that high molecular weight glycoprotein form

aggregated clusters leading to the elastic response [94].

Another kind of thin film rheology is encountered in interfacial

rheology where mobile gasliquid and liquidliquid interfaces

present in foams, emulsions, and blends (e.g. drug delivery systems,

functionalized food and health related products such as parenteral

and enteral feeding) are investigated [95,96]. These interfaces are

often stabilized by adsorption of surfactants [97,98], proteins and

partially hydrophobic biopolymers [99103] or colloidal particles. The

adsorption layer can exhibit viscoelastic, elastic or even rigid solid-

like rheological response function under lateral shear and dilatational

stresses. In case of emulsions droplets, the deformation and breakup

behavior of protein-covered emulsion drops is influenced by the

rheological properties of the adsorption layer, which prevents

coalescence and rupture of the droplet of foam bubble [103106].Further focus areas in interfacial rheology for food-related systems

are: surface interactions of small molecular weight surfactants with

proteins or other polyelectrolytes [107110], fluidization of protein

layers by competitive adsorption with surfactants [111,112], and

chemical or enzymatic interfacial cross linking of proteins [113115].

Assembly of micron-sized colloidal particles at liquid interfaces has

been extensively studied, especially in relation to the extraordinary

stability increase for particle-stabilized emulsions (Pickering emul-

sions) [116119]. Other applications of interfacial rheology addressed

the flow of saliva proteins in presence of compoundscommonlyfound

in oral health and beverage products [93].

3. Summary and perspectives

Characterizing and, ideally, understanding the rheology of food

materials is essential for numerous aspects of food science and

technology, such as the standardized characterization of raw

materials and innovative products, or for optimized industrial

processing. Classical rheometrical techniques as well as methods

adapted for the food material and the purpose of the measurement

have received considerable attention in the past decades providing a

deeper understanding of the raw material, its processing and its

underlying task in a complex food matrix.

Besides the discussed research activities some trends that have

been nucleated in the last years should be mentioned. Along with the

desire to minimize the fat content in food while keeping the full fat

mouth feel, it is of increasing interest to mimic other taste attributes

such as saltiness, bitterness, or any other offflavor of natural or added

38 P. Fischer, E.J. Windhab / Current Opinion in Colloid & Interface Science 16 (2011) 3640

7/29/2019 Rheology of Food Materials

4/5

ingredients. For example, the perception of salt significantly depends

on the food matrix, i.e. high-salt containing food can still taste dull

while low-salty food appears salty. Modification of the salt content is

therefore dependent on the food matrix and structural modifications

of the matrix leads to a different rheology and sensory attributes

[120]. Within the same context, the structuring of the oil and fats is

becoming increasingly important [121].

A recent theoretical approach to describe the rheology of gels and

concentrated food systems originates from a soft mater approachwhere gel-like, soft-glass appearance, and aging are described by the

concentration of the primary structuring ingredient (e.g. polysacchar-

ides, proteins) and the interaction potential [4,5,7,122,123]. For the

time being it is still to be proven if such concept can be generally used

(i) for multiscale food materials other than model proteins and

polysaccharides and (ii) for transient effects such as aging, gelation,

phase transitions, rearrangement, sedimentation, or creaming.

References

[1] Fischer P, Pollard M, Erni P, Marti I, Padar S. Rheological approaches to foodsystems. C R Physique 2009;10:75060.

[2] Walstra P. Physical Chemistry of Foods. New York: Marcel Dekker; 2003.[3] Trappe V, Sandkhler P. Colloidal gels: low-density disordered solid-like states.

Curr Opin Colloid Interface 2004;8:494500.[4] Donald A. Food for thought. Nat Mater 2004;3:579.[5] Mezzenga R, Schurtenberger P, Burbidge A, Michel M. Understanding foods as

soft materials. Nat Mater 2005;4:729.[6] Dickinson E. Colloid science of mixed ingredients. Soft Matter 2006;2(8):64252.[7] Stokes J, Frith W. Rheology of gelling and yielding soft matter systems. Soft

Matter 2008;4:113340.[8] Gidley M, Gothard M. Structure and rheology in plant-based foods: cell walls,

cells, and tissues. Proceedings of the 5th International Symposium on FoodRheology and Structure 2009:4651.

[9] van Puyvelde P, Antonov YA, Moldenaers P. Morphology evolution of aqueousbiopolymer emulsions during a weak shear flow. Food Hydrocoll 2003;17(3):32732.

[10] Dickinson E. Hydrocolloids at interfaces and the influence on the properties ofdispersed systems. Food Hydrocoll 2003;17(1):2539.

[11] Piazza L, Gigli J, Bulbarello A. Interfacial rheology study of espresso coffee foamstructure and properties. J Food Eng 2008;84(3):4209.

[12] Fischer P, Erni P. Emulsion drops in external flow fieldsthe role of liquidinterfaces. Curr Opin Colloid Interface Sci 2007;12:196205.

[13] McClements DJ. Food emulsions: Principles, Practice, and Techniques. 2ndEdition. Boca Raton: CRC Press; 2005.

[14] Friberg S. Food Emulsions. 4th Edition. Boca Raton, FL: CRC Press; 2003.[15] Wildmoser H, Scheiwiller J, Windhab E. Impact of disperse microstructure on

rheology and quality aspects of ice cream. LWT- Lebensmittel-Wissenschaft und-Technologie 2004;37(8):81791.

[16] Soukoulis C, Lebesi D, Tzia C. Enrichment of ice cream with dietary fibre: effectson rheological properties, ice crystallisation and glass transition phenomena.Food Chem 2009;115(2):66571.

[17] Akalin A, Karagozlu C, Ender G. Effects of aging time and storage temperature onthe rheological and sensory characteristics of whole ice cream. Milchwis-senschaft - Milk Sci Int 2008;63(3):2935.

[18] Marze S, Saint-Jalmes A, Langevin D. Protein and surfactant foams: linearrheology and dilatancy effect. Coll Surf A - Physicochem Eng Aspects 2005;263:1218.

[19] Jakubczyk E, Niranjan K. Transient development of whipped cream properties. JFood Eng 2006;77(1):7983.

[20] Chavez-Montes B, Choplin L, Schaer E. Rheological characterization of wet food

foams. J Texture Stud 2007;38(2):236

52.[21] Lal S, O'Connor C, Eyres L. Application of emulsifiers/stabilizers in dairy productsof high rheology. Adv Coll Interf Sci 2006;123126:4337.

[22] Muliawan E, Hatzikiriakos S. Rheology of mozzarella cheese: extrusion androlling. Int Dairy J 2008;18(6):61523.

[23] Burey P, Bhandari B, Rutgers R,Halley P, Torley P. Confectionery gels:a review onformulation, rheological and structural aspects. Int J Food Prop 2009;12(1):176210.

[24] Walkenstrm P, Hermansson A-M. Microstructure in relation to flow processing.Curr Opin Coll Interf Sci 2002;7:4138.

[25] Wolf B, Frith W. String phase formation in biopolymer aqueous solution blends. JRheol 2003;47(5):115170.

[26] Walther B, Walkenstrm P, Hermansson A-M, Fischer P, Windhab EJ. Flowprocessing and gel formationa promising combination for the design of theshape of gelatin drops. Food Hydrocolloids 2002;16:633.

[27] Erni P, Cramer C, Marti I, Windhab EJ, Fischer P. Continuous flow structuring ofanisotropic biopolymer particles. Adv Colloid Interf Sci 2009;150:1626.

[28] Steffe J. Rheological Methods in Food Process Engineering. East Lansing: FreemanPress; 1996.

[29] Aguilera J. Microstructure and food product engineering. Food Technol 2000;54(11):5665.

[30] Windhab E, Dressler M, Feigl K, FischerP, Megias-AlguacilD. Emulsion processingfrom single-drop deformation to design of complex processes and products.Chem Eng Sci 2005;60:210113.

[31] Genovese D, Lozano J, Rao M. The rheology of colloidal and noncolloidal fooddispersions. J Food Sci 2007;72(2):R1120.

[32] Chhabra R. Bubbles, Drops, and particles in Non-Newtonian Fluids. Boca Raton:Taylor and Francis; 2007.

[33] Beckett S. The Science of Chocolate. Cambridge: RSC Publishing; 2008.[34] Fischer P, Pollard M, Windhab E. Proceedings of the5th International Symposium

on Food Rheology and Structure. Zurich: Institute of Food Science and Nutrition;2009.[35] Singh R, Heldman D. Introduction to Food Engineering. Amsterdam: Academic

Press; 2009.[36] Ahmed J, Ramaswany H, Kasapis S, Boye J. Novel food processingEffects on

rheological and functional properties. Boca Raton: CRC Press; 2010.[37] Rosenthal A. Food Texture. Measurement and perception: Aspen Publishers,

Gaithersburg; 1999.[38] NishinariK. Rheology, food texture and mastication. J Texture Stud2004:11324.[39] Foegeding E, Drake M. Invited review: sensory and mechanical properties of

cheese texture. J Dairy Sci 2007;90(4):161124.[40] Foegeding E. Rheology and sensory texture of biopolymer gels. Curr Opin Colloid

Interface Sci 2007;12:24250.[41] Nishinari K. Texture and rheology in food and health. Food Sci Tech Res 2009;15

(2):99106.[42] Chen J. Food oral processinga review. Food Hydrocoll 2009;23(1):125.[43] Loret C, Hartmann C, Martin C. Rheological and Sensory Characterization of a

Swallowed Food Bolus. Proceedings of the 5th International Symposium on FoodRheology and Structure; 2009. p. 703.

[44] Strassburg J, Burbidge A, Hartmann C. Identification of tactile mechanisms for theevaluation of object sizes during texture perception. Food Qual Prefer 2009;20(4):32934.

[45] Lenfant F, Loret C, Pineau N. Perception of oral food breakdown. the concept ofsensory trajectory. Appetite 2009;52(3):65967.

[46] McClement D. Understanding and Controlling the Microstructure of ComplexFoods. Boca Raton: CRC Press; 2007.

[47] Hermansson A-M, Nydn M, Lorn N. Structured Biomaterials StructureDynamics and Properties. Proceedings of the 5th International Symposium onFood Rheology and Structure; 2009. p. 307.

[48] Hullberg A, Bertram H. Relationships between sensory perception and waterdistribution determined by low-field nmr t-2 relaxation in processed pork. MeatSci 2005;69(4):70920.

[49] Mossaz S, Jay P, Magnin A, Panouille M, Saint-Eve A, Dlris I, Juteau A, Souchon J.Measuring and predicting the spreading of dairy products in the mouth: sensory,instrumental and modelling approaches. Food Hydrocolloids 2010;24:6818.

[50] Servais C, Ranc H, Roberts I. Determination of chocolate viscosity. J Texture Stud2004;34:46797.

[51] Marti I, Hfler O, Fischer P, Windhab E. Rheology of concentrated suspensionscontaining mixtures of spheres and fibres. Rheol Acta 2005;44:502.

[52] Do T, Hargreaves J, Wolf B, Hort J, Mitchell J.Impact ofparticlesize distributiononrheological and textural propertiesof chocolate models with reduced fat content.

J Food Sci 2007;72:54152.[53] Gunes D, Scirocco R, Mewis J, Vermant J. Flow-induced orientation of non-

spherical particles: effect of aspect ratio and medium rheology. J Non-NewtonianFluid Mech 2008;155:3950.

[54] Do T, Vieira J, Hargreaves JM, Wolf B, Mitchell JR. Impact of limonene on thephysical properties of reduced fat chocolate. J Amer Oil Chem Soc 2008;85(10):91120.

[55] Barnes H. The yield stress a review or everything flows. J Non-Newtonian Fluid Mech 1999;81(12):13378.

[56] Moller P, Mewis J, Bonn D. Yield stress and thixotropy: on the difficulty ofmeasuring yield stresses in practice. Soft Matter 2006;2(4):27483.

[57] Barnes H. The yield stress myth? paper21 years on. Appl Rheol 2007;17(4):43110.

[58] Meeten GH. Squeeze-flow and vane rheometry of a gasliquid foam. Rheol Acta2008;47:88394.

[59] GlennIII T, Keener K,Daubert C. A mixer viscometry approach touse vane tools assteady shear rheological attachments. Appl Rheol 2000;10(2):809.

[60] Barnes HA, Nguyen QD. Rotating vane rheometrya review. J Non-NewtonianFluid Mech 2001;98:114.

[61] Roos H, Bolmstedt U, Axelsson AA. Evaluation of new methods and measuringsystems for characterisation of flow behaviour of complex foods. Appl Rheol2006;16(1):1925.

[62] Schatzmann M, Bezzola G, Minor H-E, Windhab E, FischerP. Rheometryfor large-particulated fluids: Analysis of the ball measuring system and comparison todebris flow rheometry. Rheol Acta 2009;48:71533.

[63] Lidell P, Boger DV. Yield stress measurements with the vane. J Non-NewtonianFluid Mech 1996;63(23):23561.

[64] Sherwood J, Meeten G. The use of the vane to measure the shear modulus oflinear elastic solids. J Non-Newtonian Fluid Mech 1991;41(12):10118.

[65] Baravian C, Lalante A, Parker A. Vane rheometry with a large, finite gap. ApplRheol 2002;12(2):817.

[66] Dinser S, Dual J, Husler K. Novel instrument for parallel superpositionmeasurements. Proceedings of the XVth International Congress on Rheology -AIP Conferences Proceedings 2008;1027:11868.

39P. Fischer, E.J. Windhab / Current Opinion in Colloid & Interface Science 16 (2011) 3640

7/29/2019 Rheology of Food Materials

5/5

[67] Birkhofer B,Jeelani S,Windhab E,Ouriev B, Lisner K, BraunP, Zeng Y. Monitoring offatcrystallization process using uvp-pd technique. Flow Measure Inst 2008;19:1639.

[68] Meeten GH. Yield stress of structured fluids measured by squeeze flow. RheolActa 2000;39:399408.

[69] Meeten GH. Squeeze flow of soft solids between rough surfaces. Rheol Acta2004;43:616.

[70] Burbidge A, Servais C. Squeeze flow of apparently lubricated thin films. J Non-Newtonian Fluid Mech 2004;124:11527.

[71] Engmann J, Burbidge A. Squeeze flow theory and applications to rheometry: areview. J Non-Newtonian Fluid Mech 2005;132(13):127.

[72] Dobraszczyk B, Morgenstern M. Rheology and the breadmaking process. J Cereal

Sci 2003;38:229

45.[73] Kim Y-R, Cornillon P, Campanella O, Stroshine R, Lee S, Shim J. Small and largedeformation rheology for hard wheat flour dough as influenced by mixing andresting. J Food Sci 2008;73(1):E18.

[74] van Vliet T. Strain hardening as an indicator of bread-making performance: areview with discussion. J Cereal Sci 2008;48(1):19.

[75] Lefebvre J. Nonlinear, time-dependent shear flow behaviour, and shear-inducedeffects in wheat flour dough rheology. J Cereal Sci 2009;49(2):26271.

[76] Amirkaveei S, Dai S, Newberry M, Qi F, Shahedi M, Tanner R. A comparison of therheology of four wheat flour doughs via a damage function model. Appl Rheol2009;19(3):34305.

[77] Kouassi-Koffi J, Launay B, Davidou S, Kouam L, Michon C. Lubricated squeezingflow of thin slabs of wheat flour dough: comparison of results at constant platespeed and constant extension rates. Rheol Acta 2010;49:27583.

[78] Dobraszczyk B, Morgenstern M. Biaxial extension of wheat flour doughs:lubricated squeezing flow and stress relaxation properties. J Texture Stud2008;39:496529.

[79] Charalambides M, Wanigasooriya L, Williams J, Chakrabarti S. Biaxial deforma-tion of dough using the bubble inflation technique. i. experimental. Rheol Acta

2002;41:53240.[80] Charalambides M, Wanigasooriya L, Williams J. Biaxial deformation of dough

using the bubble inflation technique. ii. numerical modelling. Rheol Acta2002;41:5418.

[81] Tanner R, Dai S, Qi F. Bread dough rheology in biaxial and step-sheardeformations. Rheol Acta 2008;47(7):73949.

[82] Charalambides M, Wanigasooriya L, Williams J, Goh S, Chakrabarti S. Largedeformation extensional rheology of bread dough. Rheol Acta 2006;46:23948.

[83] Ng T, McKinley G, Padmanabhan M. Linear to non-linear rheology of wheat flourdough. Appl Rheol 2006;16(5):26574.

[84] Ng T, McKinley G. Power law gels at finite strains: the nonlinear rheology ofgluten gels. J Rheol 2008;52(2):41749.

[85] Tanner R, Qi F, Dai S. Bread dough rheology and recoil. i. recoil and relaxation. JNon-Newton Fluid Mech 2007;143:10719.

[86] Tanner R, Qi F, Dai S. Bread dough rheology and recoil. i. rheology. J Non-Newtonian Fluid Mech 2008;148(13):3340.

[87] Clasen C, Gearing B, McKinley G. The flexure-based microgap rheometer (fmr). JRheol 2006;50(6):883905.

[88] Dresselhuis D,Klok H,Stuart M, de Vries R, vanAken G,de Hoog E. Tribology of o/w emulsions under mouth-like conditions: determinants of friction. FoodBiophys 2007;2:15871.

[89] Heyer P, LugerJ. Correlation between friction andflowof lubricating greases in anew tribometer device. Lubrication Sci 2009;21:25368.

[90] Clasen C, Kavehpour H, McKinley G. Bridging tribology and microrheology ofthinfilms. Appl Rheol 2010;20:45049.

[91] Bongaerts J, Rossetti D, Stokes J. The lubricating properties of human wholesaliva. Tribol Lett 2007;27:27787.

[92] Stokes J, Davies G. Viscoelasticity of human whole saliva collected after acid andmechanical stimulation. Biorheology 2007;44:14160.

[93] Rossetti D, Yakubov G, Stokes J, Williamson A-M, Fuller G. Interaction of humanwhole saliva and astringent dietary compounds investigated by interfacial shearrheology. Food Hydrocolloids 2008;22:106878.

[94] Davies A, Wantling E, Stokes J. The influence of beverages on the stimulation andviscoelasticity of saliva: relationship to mouthfeel? Food Hydrocolloids 2009;23:22619.

[95] EdwardsDA, Brenner H, WasanDT. Interfacial Transport Processes and Rheology.Stonheam: Butterworth-Heinemann; 1991.

[96] Miller R, Liggieri LE. Interfacial rheology. Leiden: Brill; 2009.[97] Murray B. Interfacial rheology of food emulsifiers and proteins. Curr Opin Colloid

Interface Sci 2002;7:426.[98] Erni P, Fischer P, Windhab E. Sorbitan tristearate layers at the air/water interface

studied by shear and dilatational interfacial rheology. Langmuir 2005;21(23):1055563.

[99] Dickinson E. Adsorbed protein layers at fluid interfaces: Interactions, structureand surface rheology. Colloid Surface B 1999;15(2):16176.

[100] van Vliet T, Martin A, Bos M. Gelation and interfacial behaviour of vegetableproteins. Curr Opinion Colloid Interf Sci 2002;7:4628.

[101] Casco Pereira LG, Thodoly O, Blanch HW, Radke CJ. Dilatational rheology of bsa

conformers at the air/water interface. Langmuir 2003;19:2349

56.[102] FreerEM, YimKS, FullerGG, Radke CJ.Interfacialrheologyof globular andflexibleproteins at the hexadecane/water interface: comparison of shear and dilatationdeformation. J Phys Chem B 2004;108(12):383544.

[103] Erni P, Windhab EJ, Gunde R, Graber M, Pfister B, Parker A, Fischer P. Interfacialrheology of surface-active biopolymers: acacia senegal gum versus hydropho-bically modified starch. Biomacromolecules 2007;8:345866.

[104] Dickinson E. Structure, stability and rheology of flocculated emulsions. CurrOpinion Colloid Interf Sci 1998;3:6338.

[105] Erni P, Fischer P, Windhab EJ.Deformationof single emulsion drops covered witha viscoelastic adsorbed protein layer in simple shear flow. Appl Phy Lett 2005;87(24):244104.

[106] Erni P, Fischer P, Herle V, Haug M, Windhab EJ. Complex interfaces and their rolein protein-stabilized soft materials. Chemphyschem 2008;9(13):18337.

[107] Monteux C, Fuller G, Bergeron V. Shear and dilational surface rheology ofoppositely charged polyelectrolyte/surfactant microgels adsorbed at the air/water interface. influence on foam stability. J Phys Chem B 2004;108:16473.

[108] Gunning P, Mackie A, Gunning A, Woodward N, Wilde P, Morris V. Effect ofsurfactant type on surfactant/protein interactions at the air/water interface.

Biomacromolecules 2004;5:984.[109] Wilde P, Mackie A, Husband P, Gunning F, Morris V. Proteins and emulsifiers at

liquid interfaces. Adv Colloid Interface Sci 2004;108109:6371.[110] Miquelim J, Lannes S, Mezzenga R. ph influence on the stability of foams with

protein-polysaccharide complexes at their interfaces. Food Hydrocolloids2010;24:398405.

[111] Dickinson E, Hong S-T. Surface coverage of -lactoglobulin at the oilwaterinterface: Influence of protein heat treatment and various emulsifiers. J AgricFood Chem 1994;42:16026.

[112] Green R, Su T, Lu J, Webster J, Penfold J. Competitive adsorption of lysozyme andc12e5 at the air/liquid interface. Phys Chem Chem Phys 2000;2:52229.

[113] Faergemand M, Murray B. Interfacial dilatational properties of milk proteinscross-linked by transglutaminase. J Agric Food Chem 1998;46:88490.

[114] Romoscanu A, Mezzenga R. Cross linking and rheological characterization ofadsorbed protein layers at the oil/water interface. Langmuir 2005;21:9689.

[115] Martin A, Stuart M, Bos M, van Vliet T. Correlation between mechanical behaviorof protein films at the air/water interface and intrinsic stability of proteinmolecules. Langmuir 2005;21:4083.

[116] Sacanna S, Kegel W, Philipse A. Thermodynamically stable pickering emulsions.Phys Rev Lett 2007;98:158301.

[117] Bresme F, Oettel M. Nanoparticles at fluid interfaces. J Phys Condens Matter2007;17:413101.

[118] Binks B. Particles as surfactantssimilarities and differences. Curr Opin ColloidInterface Sci 2002;7:2141.

[119] Park B,Pantina J,FurstE, OettelM, Reynaert S, Vermant J. Directmeasurements ofthe effects of salt and surfactant on interaction forces between colloidal particlesat water/oil interfaces. Langmuir 2008;24:1686.

[120] Koliandris A-L, Morris C, Hewson L, Hort J, Taylor A, Wolf B. Correlation betweenslatiness perception and shear flow behaviour for viscous solutions. FoodHydrocolloids 2010;24:7929.

[121] Marangoni A. Novel strategies for nanostructuring liquid oils into functional fats.Proceedings of the 5th International Symposium on Food Rheology andStructure; 2009. p. 3845.

[122] Mewis J, Dullaert K. A structural kinetics model for thixotropy. J Non-NewtonianFluid Mech 2006;139(12):2130.

[123] Fuchs M. Non-Linear Rheological Properties of Dense Colloidal Dispersions.Berlin: Springer; 2009.

40 P. Fischer, E.J. Windhab / Current Opinion in Colloid & Interface Science 16 (2011) 3640