Explanation and Evaluation of Mouthfeel
s e p e r uipm o rh o eq& he • w tsy rs ics vmi i rvrk d ra a e ggr p s o n oo e & w a mr r s r r p r d Tim’s Top Tips - Explanation and Evaluation ofe Mouthfeel• i n a h p s a n t o t p a i h n re r & s a m k e e r • n e c m i s o s n u t e w r n m c i e i t e f c d s s i s n n m c i c e a u i e c r f r g t i p a s c s f a n i n e r n i i t y u s p r s g s t m e t n s • e i y r s r t u t g e s d c s n i e u n i f mt i t i ry d s c l • e n e e i t o p mp g • s s y n l i d • i y g t o s l r r n s p o t i e e s s t t • s u s m • t e d r y t c l s e n
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i l v o o u t r a c t a e c e a s i RHEO253 e s r i c t i r e n v p u d p a r t o n e a a m g s r r • e s e t od s e t p l n • e www.rheologysolutions.com n a Page 1 a m c s t i e e r s t t v o e r m s l i e u • l p a s s r t a p t r i u t s c d o s is n e l n i p l p a a Tim’s Top Tips - Explanation and Evaluation of Mouthfeel
Company Profile Contact Details
Rheology Solutions Pty Ltd is a specialist sales and service Rheology Solutions Pty Ltd organisation dedicated to the science of materials Address: 15 -19 Hillside Street, Bacchus Marsh, Victoria, 3340 characterisation and are the exclusive Australian distributor for PO Box 754, Bacchus Marsh, Victoria, 3340 the brand names HAAKE, NESLAB, PRISM and CAHN from Phone: 03 5367 7477 Thermo Fisher Scientific, Optical Control Systems, Schleibinger Fax: 03 5367 6477 Gerate and Marimex Industries Corporation range of equipment Email: [email protected] and instruments, and they also distribute the Shimadzu range of Website: www.rheologysolutions.com tensile testers and texture analysers.
Rheology Solutions recognises the importance of specialisation Disclaimer and dedication to a specific science and as such provides full technical support and service throughout Australia. The company The information contained in this report is not intended for direct goal is to integrate industry experience and materials use as a tool for process development. It is a guide only. This characterisation techniques to provide practical solutions for document remains the property of Rheology Solutions Pty Ltd, customers. and may not be reproduced or altered in any way without the written permission of the owners. Rheology Solutions has an established applications laboratory equipped with a comprehensive range of instruments to meet the Written by Dr. T. Kealy requirements of material characterisation. Specialist contract Technical Manager testing services are also available and contracts can be tailored Rheology Solutions Pty Ltd to suit discrete tests or protracted testing requirements involving a series of tests over a period of weeks or months. © Rheology Solutions Pty Ltd 2006
A range of seminars and application specific workshops as well as product launches and demonstrations are provided throughout Australia. The seminars and workshops are designed to meet the needs of specific customer and industry applications. Rheology Solutions has its head office in Victoria and works with a team of specialist sales and factory trained service personnel throughout Australia. The combined experience of this team ensures that Rheology Solutions are able to provide their customers with access to the products to ensure that the right technical support and service is provided.
Page 2 (4) [email protected] p k se ent p e r uipm o rh o eq & he • w tsy rs ics vmi i rvrk d rra a eo n gg p s oo e & w a r r s Tim’s Top Tips - Explanation andr Evaluation of rMouthfeelmp r d e • i n a h p s a n t o t p a i h n e r & s r a m k e e r • n e m i s c o s n u t m c e w r n i i t e e f c s s i d s n m c n i c e a u i e c r f r g t i p a s c s f a n Tim’s Top Tips: Rheology Solutions for the Food Industriesr i n e n t i y i u s p r s g s t m e t n s • e i y r s r t u t g e s d c s n i e u n i f mt i t i Explanation and Evaluation of Mouthfeelry d s c l • e n e e o i t
g p mp • s s y n l • i d i y g t o s l r r n s p o t i e e s s t t • s u s m
t • e Key Words: Mouthfeel, rheology, rotational, extensional, universal tester,d taster y panel, t l c e s n
a r i o t
r m c a p
t • solid, semi-solid, liquid, viscosity, viscometer, rheometer, viscoelastic, force andy displacementa n l r n i r
g o t
o o
m f
n p n c i measurements. e o t r s
s • s c o
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s t n t s t s
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About The Author Introduction u
C r
o n y m t r
s
Q
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s
p r
c l
n t
C
i
a s
g
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Q
n Tim has a background in i
Often the food industry mustg overcome problems related to (and n
i
s i t
l
t
n
t
i
a p
g
s
n engineering and specifically in t
often dominated by) the flow propertiesc of their product, though
o
e i
s n
e
i
t t
e
t •
rheology, with a B.Eng and Ph.D. in t m
p
r the relationship between these properties and s production
s
u
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k
t
r
t
Chemical Engineering and has held c t
n
• related issues are not alwaysm immediately apparent. It is the
s a
k e
l
o
s
n
c
t
i t postdoctoral research positions in b
purpose of this series of articles, “Rheologym solutions for the a s
l n
u
a g n
l e
b
engineering rheology. Tim's r
o n
t
food industries”, to help illuminatee the issues faced by the
i
s
m
b n t
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s
n u
research has continued for the last o &
i
a
industry, how they relate to the flow propertiesr of the problem e
b
t r
c t
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g
s
seven years and recent interests e
a
•
k
n
materials and how they can be successfullyn measured and
b
i
c i
c
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b
and publications include the a r s
•
l g
controlled with a view to betteru processing.
e o
r
b n
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application of rheology and rheometry to mineral, food, polymer i r
t a
l
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s o
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o t i s o
and surface coatings systems. His current position encompasses e
r r
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t t
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the managment of customer contract testing and also includes a
a
Definitions e c i
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customer focussed education and training. Additionally he is l
t
o
o
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s
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available to provide technical input for existing or proposed s h
a
o
Mouthfeel is the textural part of the experiencem of the consumer r o
t p c
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i
a
l t o •
materials characterisation systems for both laboratory and • r
a p
when chewing and swallowing food. The foods canh be liquid,
s
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production. k a
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semi-solid or solid and the elements of mouthfeelo can be p
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measured relative to the various physical propertiesn of the food k s
on r
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in deformation and flow. s
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Table Of Contents r
w s
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t • l t
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p a
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Introduction...... 3 t r e
Background and Discussion c
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Definitions ...... 3 c ts
on r
o
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s •
a c t
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s
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Background and discussion ...... 3 Traditionally, taste panels have been used to evaluatei mouthfeel
i
s
r
c
m v
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r
u s
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d r
Mouthfeel analysis using uniaxial but the results are often inconclusive unless large numberst of t
t
a
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s
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r
r r
a
t n
participants and a lot of time are available. Sophisticatedm and
e
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compression or extension – x
t
f
d a
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g a
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sensitive measurement techniques and equipment nowu allow
n r c
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solid and semi-solid materials ...... 4 w t e
t
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s
much of this work to be done using scientific instruments. Inl the
r
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Mouthfeel analysis using rotational t e
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case of the relationship between mouthfeel and liquid (and e
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viscometers and rheometers n
semi-solid) flow properties, the important variables may includea
c
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s
m t y
h
l c
t
and extensional rheometers – liquids ...... 5 some, or all, of extensional viscosity the elastic and viscousf s
n
•
o
i
o
o p
s e
t
w
moduli the complex viscosity, shear viscosity, thixotropy etc ande
e
h Mouthfeel analysis using a taste panel – t •
c
s t
d
r
s
n •
e
can be measured on Controlled Stress (CS) rheometersr or
o u
t
all edible foodstuffs ...... 8 e
i s
t e
a o
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e
c c
s
m
Controlled Rate (CR) viscometers. For solid and semi-solid d s
i
r
y
Summary ...... 9 e
d g l
e
t
u
e
o n
materials, properties like adhesiveness, cohesiveness, brittleness, h
a
o i
t
d
p c
Other information for food industries ...... 10 c
n
i
i
r
and hardness etc, measured according to Szczeniak on a texture o
n
d
t g a o
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Food dictionary ...... 11 n i
t
i
analyser have been shown to be important for the predictiont of d d
s n e a
•
i t n
s m i l
Information request form ...... 15 a mouthfeel. a o
r
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t
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a d
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r e i
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c e a e s i e s r i c t i r e n v p d u p r t a o n e g a a m s r r • e e s t od s p e t l n www.rheologysolutions.com (5) Page 3• e a n m a c s t i e e r s t v t o e r m s l i p e u • l a s r t a p s t r i u t d s o c s s e i n np l Tim’s Top Tips - Explanation and Evaluation of Mouthfeel
Mouthfeel analysis using uniaxial compression or extension – solid and semi-solid materials
Rheology Solutions Instrument Shimadzu EZ Test
Texture analyser for measuring the flow and deformation of solid and semi-solid foods.
The efficiency and suitability of instrumentation for mouthfeel testing for solid and semi-solid materials using uniaxial compression or extension is related to the geometry of the probe • Repeatability: and to the textural characteristic which one is trying to emulate. A relatively large number of tests (often up to 10 or 20) are often In general, uniaxial testing machines are used for this purpose necessary in order that a statistically relevant measurement is and the tests involve displacement of the foodstuff either by made. This is particularly true of semi-solid materials eg forcing the probe downwards, compressing or cleaving the spreadable cheeses. The number of tests is often high relative to material and measuring the force required to do so, or by moving those required on a rheometer, for example, but the time and the probe upwards, allowing the material to relax, or stretching expense is usually lower than that associated with taste panels. the material. This repeatability issue is not in general related to the measurement or the instrument, more often to inconsistent Potential problems with these measurements include: sample preparation or to the heterogeneous nature of many food products. In the cases where the repeatability is related to • Which is the correct sensor? the measurement, then a change in conditions, such as increasing or decreasing the speed of the cross-head, or There is a large variety of different sensors. The list of sensor reviewing the suitability of a particular load cell or sensor may be geometries includes flat plates, conical probes, 2- and 3-point necessary. Often, the same load cell can not be used to measure bending jigs, tooth presses and many other custom built sensors all of the products a company manufactures (eg for a dairy for individual applications. This diversity is not itself a problem, company, yoghurt, spreadable cheese and hard (eg cheddar) and may in fact help to solve problems, but care must be taken cheese may all require different load cells so that the best data that the most appropriate one is chosen for the job. Often the can be gathered. changing resistance of a product to compressive (eg while measuring the changes in hardness or crispiness over time or in different storage atmospheres) or extensional forces (eg for • Which is the best test method? measuring the suitability of different packaging sealants for different storage conditions) is an indication of the continuing suitability of the material for consumption.
Textural characteristics as defined by Szczeniak for textural analyses
Page 4 (4) [email protected] p k se ent p e r uipm o rh o eq & he • w tsy rs ics vmi i rvrk d rra a eo n gg p s oo e & w a r r s Tim’s Top Tips - Explanation andr Evaluation of rMouthfeelmp r d e • i n a h p s a n t o t p a i h n e r & s r a m k e e r • n e m i s c o s n u t m c e w r n i i t e e f c s s i d s n m c n i c e a u i e c r f r g t i Szczeniak, at General Foods in the USA, standardised many of p a c Mouthfeel analysis using n s s f a i n e r n t i y i these measurements and defined many of the textural properties u s p r s g s t m e rotational viscometers andt n measured today, for example hardness, cohesiveness, brittleness s • e i y r s r t u t g e s d c s elastic quality and so on. The relevance of these textural n i e rheometers and extensional u n i f mt i t i ry d s c l characteristics to mouthfeel is that, these measurable quantities • e n e e o i rheometers – liquidst g p mp • have been shown in many research papers to relate directly to s s y n l • i d i y g t o s l r r n the experience of the consumer when chewing and swallowing s p o t i e e s s t t • s food. u s m t • e d r y t l c e s n
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c e a e s i e s r i c t i r e n v p d u p r t a o n e g a a m s r r • e e s t od s p e t l n www.rheologysolutions.com (5) Page 5• e a n m a c s t i e e r s t v t o e r m s l i p e u • l a s r t a p s t r i u t d s o c s s e i n np l Tim’s Top Tips - Explanation and Evaluation of Mouthfeel
Shear viscosity is simply the resistance of the material to flow. • Viscoelastic properties difficult to understand: Except for a few materials, shear viscosity is a function of shear rate, and should be measured at a variety of shear rates so that a clear picture of the behaviour of the material is obtained for mouthfeel analyses – chewing and swallowing occur at many different shear rates due to the diverse movements of the jaws and tongue. Rheology Solutions Instrument HAAKE MARS • Viscoelastic properties not repeatable: CS rheometer for measuring the flow properties of liquid foods.
In general the properties measured are the viscous and elastic moduli and the complex viscosity. The complex viscosity is a measure of the resistance of the material to flow and the viscosity at a variety of frequencies of oscillation (analogous to shear rate) should be known to fully define the material. Higher viscosity materials will require higher forces to initiate and continue flow. At low frequencies, for polymeric systems (starch, guar, xanthan, carageenan gums etc), the viscoelastic moduli show the contribution of high Molecular Weight (MW) species, the crossover point of the moduli shows the point at which the moduli are equal and is often used as a quality control point for materials. Changes in the magnitude of the moduli at the crossover point imply changes in molecular weight distribution, and changes in the frequency at which the crossover point In the LVE, properties are independent of the amplitude or occurs implies a change in the mean MW of the system. Some force applied during oscillatory measurements practical and theoretical training can often help nervous operators overcome the perceived complexity of viscoelastic Viscoelastic properties are generally measured by means of a measurements and assessing the data. frequency sweep (i.e. oscillating the sensor at different rates in the sample) in the Linear Viscoelastic Envelope (LVE). If the measurements are not carried out in the LVE they will not be repeatable, and most likely will not be comparable between materials.
Viscoelastic flow properties tell us about the undisturbed (in the LVE) structure of the material
Page 6 (4) [email protected] p k se ent p e r uipm o rh o eq & he • w tsy rs ics vmi i rvrk d rra a eo n gg p s oo e & w a r r s Tim’s Top Tips - Explanation andr Evaluation of rMouthfeelmp r d e • i n a h p s a n t o t p a i h n e r & s r a m k e e r • n e m i s c o s n u t m c e w r n i i t e e f c s s i d s n m c n i c e a u i e c r f r g t i • Relative vs absolute data: p a s c s f a n i n e r n t i y i u s p r s g s t m e t n s • e i y r s r t u t g e s d c s n i e u n i f mt i t i ry d s c l • e n e e o i t
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c e a e s i e s r i c t i r e n v p d u p r t a o n e g a a m s r r • e e s t od s p e t l n www.rheologysolutions.com (5) Page 7• e a n m a c s t i e e r s t v t o e r m s l i p e u • l a s r t a p s t r i u t d s o c s s e i n np l Tim’s Top Tips - Explanation and Evaluation of Mouthfeel
Mouthfeel analysis using a taste Potential problems may include: panel – all edible foodstuffs • Panellist condition: The events, culinary or otherwise, of the preceding few days, hours or minutes may have an unknown influence on the panellist’s impression of the food which they are testing. This can make it difficult for the panellists to agree on their impressions.
• Time and expense: Large numbers of people and large amounts of time are necessary for these types of tests. Large numbers can often be reduced by training the panel before the testing begins.
• Reproducibility: Individuals can be highly subjective, and reproducibility may be an issue. Different demographic groups may also react Taste panels are the ultimate approval mechanism for foods, no differently to the same material. Different taste panels can machine can perfectly imitate the complexities of simultaneously be convened to cater for different target markets. Using chewing, smelling and tasting. standard terms, (like those defined by Szczeniak) which have been well defined and explained to the panellists is a good Texture analysis using a taste panel is achieved using a group of technique for at least reducing the possibility of these errors. people representative of the general population of interest to the product manufacturers. These panellists may be trained, in • The measurements are not absolute: which case, fewer of them are generally required since Therefore it is difficult to compare results from different terminology and scoring for the potentially confusing foodstuffs or from different panels. The use of standard nomenclature of texture analysis is simplified when the terms and definitions can allow some comparisons with the participants fully understand it. If the panellists are not trained, mouthfeel of previously researched materials. the numbers required are usually greater, and the time required to collect the relevant data is also greater. This technique, • The influence of taste, odour etc: however has the advantage that it is being carried out by Taste and odour can have an effect on the perception of humans, and therefore the complexities of tasting, chewing and texture, and it may be difficult for panellists to separate these swallowing are all accounted for. Both solid and liquid foods can effects. The best solution is to train the panel well, and if be tested. possible to use instrumental techniques to check panel data.
Page 8 (4) [email protected] p k se ent p e r uipm o rh o eq & he • w tsy rs ics vmi i rvrk d rra a eo n gg p s oo e & w a r r s Tim’s Top Tips - Explanation andr Evaluation of rMouthfeelmp r d e • i n a h p s a n t o t p a i h n e r & s r a m k e e r • n e m i s c o s n u t m c e w r n i i t e e f c s s i d s n m c n i c e a u i e c r f r g t i Determining the most suitablep type of instrumenta is not simplyc a Summary n s s f a i n e r n t i y i matter of adding up the ranking for each.u Rather,s identify pwhich r s g s t m e t n measurement technique,s variable •etce is mosti relevanty and r s r t Table 1 summarises the possibilities for measuring mouthfeel u t g e s d c s appropriate for your application/product.n i Often,e more than one u n i f mt using the techniques discussed. Each of the techniques is ranked i t i ry d s c l technique is required to ensure• consistency, reproducibilitye n and e e o i between 0 and 5 for each of the potential issues and solutions, t
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Technique: Uniaxial Force CR Viscometers CS Rheometersd Extensionalt Taste Panel s
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Test Method a o
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c e a e s i e s r i c t i r e n v p d u p r t a o n e g a a m s r r • e e s t od s p e t l n www.rheologysolutions.com (5) Page 9• e a n m a c s t i e e r s t v t o e r m s l i p e u • l a s r t a p s t r i u t d s o c s s e i n np l Tim’s Top Tips - Explanation and Evaluation of Mouthfeel
Contact Details Other Notes Available in the Tim’s Top Tips - Rheology Solutions for the Food Industries Series are:
• Explanation and Evaluation of Shelf life (Rheo254) • Explanation and Evaluation of Processability (Rheo255) • Explanation and Evaluation of Cohesiveness (Rheo256)
Other Information Available for the Food Industries include:
• Rheology Solutions for Food Industries Information Kit • Applications Laboratory and Contract Testing Capabilities Statement for Food Industries • Technical Literature for Food Industries Head Office Rheology Solutions Pty Ltd
Address: 15 -19 Hillside Street, Bacchus Marsh, Victoria, 3340 PO Box 754, Bacchus Marsh, Victoria, 3340 Phone: 03 5367 7477 Fax: 03 5367 6477 Email: [email protected] Website: www.rheologysolutions.com
Managing Director – Pat Griffin Email: [email protected]
Technical Manager – Dr Tim Kealy Email: [email protected]
Service Engineer – Richard Donaldson Email: [email protected] [email protected]
Focused on providing our customers with materials characterisation solutions through knowledge, experience and support.
Page 10 (4) [email protected] Tim’s Top Tips - Explanation and Evaluation of Mouthfeel
Food Dictionary
Industry Term: Adhesiveness Definition: The force require to remove food which has bonded to the hands during handling or to the roof of the mouth during eating. Governing Properties: This is a solid rheological (mechanical) property, measured according to Szczeniak on a texture analyser. Rheology Solutions Instrument: Shimadzu EZ Test.
Industry Term: Brittleness Definition: The breakdown force of food in the mouth. Governing Properties: This is a solid rheological (mechanical) property which is measured according to Szczeniak on a texture analyser. Rheology Solutions Instrument: Shimadzu EZ Test.
Industry Term: Cohesiveness Definition: The extent of deformation and destruction of a product when a load is applied to it. Governing Properties: This is a solid rheological (mechanical) property which is measured according to Szczeniak on a texture analyser. Rheology Solutions Instrument: Shimadzu EZ Test.
Industry Term: Complex Viscosity Definition: The viscosity measured by dynamic rheometry, related to both the viscous and elastic portions of flow for a viscoelastic fluid. Governing Properties: This is a property governed by the viscoelastic properties of the material - elastic and viscous moduli (G’ and G’’). It is measured on a CS rheometer using a frequency sweep. Rheology Solutions Instrument: HAAKE RheoStress, HAAKE MARS.
Industry Term: Controlled Stress (CS) Ramp Definition: A technique for testing materials. The shear stress is gradually increased, rather changed in a stepwise fashion. Governing Properties: The capabilities of the rheometer will define its ability to conduct a CS ramp. Rheology Solutions Instrument: HAAKE RheoStress, HAAKE MARS.
Industry Term: Crispiness Definition: The crispiness (or brittleness) of a product is the difference between the force required to fracture and the point at which the load begins to increase again due to compression of the material. Governing Properties: This is a solid rheological (mechanical) property which is measured according to Szczeniak on a texture analyser. Rheology Solutions Instrument: Shimadzu EZ Test.
[email protected] (00) (5) © 2005 Rheology Solutions Page Pty Ltd11 p k se ent p e r uipm o rh o eq & he • w tsy rs ics vmi i rvrk d rra a eo n gg p s oo e & w a r r s Tim’s Top Tips - Explanation andr Evaluation of rMouthfeelmp r d e • i n a h p s a n t o t p a i h n e r & s r a m k e e r • n e m i s c o s n u t m c e w r n i i t e e f c s s i d s n m c n i c e a u i e c r f r g t i Industry Term: Crossover Point p a s c s f a n i n e r n t i y i Definition: The point at which the viscous modulus is quantitatively equalu in to the elastics modulus.p r s g s t m e t n s • e i y Governing Properties: This is a property governed by the viscoelastic properties of the material - elasticr and u s r t s t g e s d c e viscous moduli (G’ and G’’). It is measured on a CS rheometern i using a frequency sweep. u n i f mt i t i ry d s c l Rheology Solutions Instrument: HAAKE RheoStress, HAAKE MARS. • e n e e o i t
g p mp • s s y n l • i d i y g t o s l r r n s p o t i e e s s t t • s Industry Term: Deformation u s m t • e d r y t l c e s n Definition: The movement of an element of a material, usuallya as ra resulti of someo appliedt force r m c a p
t • y a n l r Governing Properties: The rate of deformation (shear rate) due to an appliedn forcei is dependent on ther resistance g o t
o o
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n p n c i of the material – it’s viscosity in the case of a liquid,e or rigidity in the case of a solid. o t r s
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m e f Rheology Solutions Instrument: HAAKE ViscoTester 550, HAAKE RotoVisco, HAAKERheoStress,s • HAAKE MARS, Marimex •
t t e
s
s t n t s t s
ViscoScope, Shimadzu EZ Test. t c
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d t
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Industry Term: Elastic and Viscous Moduli • c
Q
n i
g n
i
s i t
l
t
n
t
i
Definition: Many liquids have a solid-like (elastic) component and a liquid-like p (viscous) component. a
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Industry Term: Elastic Quality n
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Definition: a
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succession to a food product. t t
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Governing Properties: This is a solid rheological (mechanical) property which is measured according to Szczeniaka
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Rheology Solutions Instrument: Shimadzu EZ Test. i
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Industry Term: Extensional Viscosity on r
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a
a
Definition: The extensional viscosity of a liquid is the resistance to flow of the liquid as it r is being
w s
s
on
c
r i
e
i
i
i
r
t • l t
a
stretched. This is a different property to (and independent of) either the e shear viscosity or
e
p a
s t
p
s
r p
c
i
m
e
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the complex viscosity. a r
o
t
r
e
c
•
t e • a
s
c
Governing Properties: The extensional viscosity depends on the temperature, the rate of deformation of thei
h
m
a v
c ts
on r
o
i
n
s
liquid. It can be measured on an extensional viscometer. •
a c t
l
e
s
a h
s a
i
i
s
r
c
m v
Rheology Solutions Instrument: i HAAKE CaBER r
e
r
u s
e
• l
e d r t
t
t
a
a u
s
i c s
r
r r
a t
n
m
e e
i r
x
t
f
d a
e
g a
o h u
n Industry Term: Flow r c
i m
w t e
t
s
e c x
f
s l
Definition: Measure of the ability of a sample to be moved (by gravity or other force). r
e n
o a e
c
i
t e
s
r i
e
w
Governing Properties: The rate of flow of a liquid is governed by its properties in shear, includingr the yield point e c
c
n
t e
s
e
i
r
n
a
c
e at low shear, measured with a CR viscometer, and by the viscoelastic propertiesm of the
e w
i
s
m t y
h
l c
t
f
s
n
•
liquid, as measured on a frequency sweep by a CS rheometer. CR measurementso can often
i
o
o p
s e
t
w
e
be made in-line. e
h t •
c
s t
d
r
s
n •
e
Rheology Solutions Instrument: HAAKE ViscoTester 550, HAAKE RotoVisco, HAAKE RheoStress, HAAKE MARS,r Marimex o u t e
i s
t e
a o
c
e
c c
s
m
ViscoScope. d s
i
r
y
e
d g l
e
t
u
e
o
n
h
a
o i
t
d
p
c
c
n
i
i
r
o
n
d
t g a o
o
e r
f
n i
t
i Industry Term: Frequency Sweep d
t d
s n e a
•
i t n
s Definition: This technique is an analysis of the dependency of the rate dependent viscoelasticm l i
a
a o
r
e i
o n c
t
i t t r
properties; it is usually carried out in the LVE of the test material. a s t
a d
• g y n s
r e i
s l
Governing Properties: o N/A d o n o c r a C
t e n Rheology Solutions Instrument: HAAKE RheoStress, HAAKE MARS. e g
Q c n i r o r
i l o v u t o r a c t a
c e a e s i e s r i c t i r e n v p d u p r t a o n e g a a m s r r • e e s t od s p e t l n Page© 2005 12 Rheology Solutions Pty Ltd (00) (4) [email protected]• e a n m a c s t i e e r s t v t o e r m s l i p e u • l a s r t a p s t r i u t d s o c s s e i n np l Tim’s Top Tips - Explanation and Evaluation of Mouthfeel
Industry Term: Hardness Definition: This describes a product which displays substantial resistance to deformation or breaking. It is the perceived force required to break the sample into several pieces during the first bite by the molars. Governing Properties: This is a solid rheological (mechanical) property which is measured according to Szczeniak on a texture analyser. Rheology Solutions Instrument: Shimadzu EZ Test.
Industry Term: Linear Viscoelastic Envelope (LVE) Definition: The LVE is the region in which the internal structure of a material remains unchanged as the imposed stress or deformation is gradually increased. Governing Properties: Measured on a CS rheometer using a stress sweep or a strain sweep. Rheology Solutions Instrument: HAAKE RheoStress, HAAKE MARS.
Industry Term: Mouthfeel Definition: A combined experience from the sensations of the skin in the mouth during and/or after ingestion. Governing Properties: Liquid properties – Extensional Viscosity, G’, G’’, h*, Shear Viscosity, Thixotropy etc. Also related to solid mechanical properties like adhesiveness, cohesiveness, brittleness, hardness etc, measured according to Szczeniak on a texture analyser. Rheology Solutions Instrument: HAAKE CaBER 1, HAAKE ViscoTester 550, HAAKE RotoVisco, HAAKE RheoStress, HAAKE MARS, Shimadzu EZ Test.
Industry Term: Rheometer Definition: An instrument designed for the measurement of viscous and viscoelastic flow properties at specified temperature and atmospheric conditions, by measuring the force required to move one layer over another without turbulence. Governing Properties: Rheometers often have air bearings, making them highly sensitive to small variations in load or displacement and can operate in rotation or oscillation for Controlled Rate or Controlled Stress modes. Some rheometers have mechanical bearings, but in general they do not have the required sensitivity to make good use of CS mode in these cases and can not run oscillatory measurements well (or at all). Rheology Solutions Instrument: HAAKE RheoStress, HAAKE MARS.
Industry Term: Shear Rate Definition: This is the rate of change of deformation through an element of a fluid due to an imposed deformation or stress. Governing Properties: The shear rate is dependent on the geometry of the deformed element, and on the force or displacement imposed on it. Shear rate can be measured on a CS rheometer, or can be imposed by a CR viscometer. Rheology Solutions Instrument: HAAKE ViscoTester 550, HAAKE RotoVisco, HAAKE RheoStress, HAAKE MARS.
Industry Term: Shear Stress Definition: This is the force per unit area imposed on an element of fluid. Governing Properties: The shear stress is dependent on the geometry of the fluid element and can be measured by a CR viscometer and may be imposed by a CS rheometer. Rheology Solutions Instrument: HAAKE ViscoTester 550, HAAKE RotoVisco, HAAKE RheoStress, HAAKE MARS.
[email protected] (00) (5) © 2005 Rheology Solutions Page Pty Ltd13 p k se ent p e r uipm o rh o eq & he • w tsy rs ics vmi i rvrk d rra a eo n gg p s oo e & w a r r s Tim’s Top Tips - Explanation andr Evaluation of rMouthfeelmp r d e • i n a h p s a n t o t p a i h n e r & s r a m k e e r • n e m i s c o s n u t m c e w r n i i t e e f c s s i d s n m c n i c e a u i e c r f Industry Term: Shear Viscosity r g t i p a s c s f a n i n e r n t i y i Definition: The shear viscosity is the resistance of a fluid to flow when a shearu stress iss exertedp upon r s g s t m e t n it. s • e i y r s r t u t g e s d c s Governing Properties: Shear viscosity depends on temperature and usually shear raten i or shear estress. It can be u n i f mt i t i ry d s c l measured on a viscometer or a rheometer, using viscometric• measuringe geometries.n e e o i t
g p mp • Rheology Solutions Instrument: HAAKE ViscoTester 550, HAAKE RotoVisco, HAAKE RheoStress.s s y n l • i d i y g t o s l r r n s p o t i e e s s t t • s u s m
t • e d r y t l c e s n Industry Term: Thixotropy a r i o t
r m c a p
t • y a n l r Definition: n r Thixotropic fluids show shear thinning behaviour combinedi with a time dependency. The
g o t
o o
m f
n p n c viscosity of a thixotropic fluid drops when subjected to a constanti shear rate for a period e o t r s
s • s c o
m
e f of time. The viscosity of thixotropic fluids often recoverss substantially over a period of •
•
t t e
s
s t n t s t time after the shearing forces have been removed. s t c
e c m y
n a
e s u
m r t Governing Properties: Thixotropy depends on the rate of structural recovery in the material. It cane be measured
d t
s
u
C r
o n y m t r
s
Q
using a flow curve on a CR or CS instrument, or by measuringo the recovery u of the moduli
s
p r
c l
n t
C
i
a s
after shearing on a CS rheometer. g • c
Q
n i
g n
i
s i t
l
t
Rheology Solutions Instrument: HAAKE ViscoTester 550, HAAKE RotoVisco, HAAKE RheoStress,t n HAAKE MARS.
i
a p
g
s
n
t
c
o
e i
s n
e
i
t t
e
t •
t
m
p
r s
s
u
o
e e
k
t
r
t
c
t
n
• m
s a
k e
l
Industry Term: Viscoelastic Properties o
s
n
c
t
i t b
m
a s
l n
Definition: These are properties of the material at rest. See ‘Complex Viscosity’,u ‘Elastic and Viscous a g n
l e b r
o n
t
e
i
s
m
b n
Moduli’, ‘Crossover Point’. t
r
s
n u
o &
i
a
r
e
b
t
r c
Governing Properties: Governed by the structural properties of the material at rest, measuredt on a CS rheometer.
r
g
s
e
a
•
k n
n
b
i
c i
Rheology Solutions Instrument: HAAKE RheoStress, HAAKE MARS. c
t y
b
a
r s
•
l g
u
e o
r
b n
t y t
i
r
t a
l
• n
r
s o
a
o
t i s
o e
r r
t
a b
b
r r e e
l
Industry Term: Viscoelastic Moduli a
t t
a l
o
a
a
e c i
b s
Definition: The collective name for the elastic and viscous moduli, G’ and G’’. r
a
m
m
n
•
e l
t
o
o
• y
i
s
a
Governing Properties: Usually measured using a CS rheometer. e r t
n
s
h
a o
m
r o
t
p c
i
Rheology Solutions Instrument: HAAKE RheoStress, HAAKE MARS. i
a
l t o •
•
r
a p
h
s
o
c s
e
p
i
p
b
c l k
a
i
r a o
p
l v
•
o
h
r p
s
s
e
a w
n
k
Industry Term: Viscometer s
on r
o • • i
i
o t
& t
s
Definition: An instrument for measuring the viscosity of a liquid at specified a temperature and
a
r
w s
s
on
c
r i
e
i
i
i
r
t • l t
atmospheric conditions, by measuring the force required to movea one layer over another
e
e
p a
s t
p
s
r p
c
i
m
e
r
a without turbulence; also referred to as viscometer. e
a
r
o
t
r
e
c
•
t
e
• a
Governing Properties: Viscometers usually have mechanical bearings in their motor and generally operates in c
i
h
m
a v
c ts
on r
o
i
rotational mode only. n
s •
a c t
l
e
s
a h
s a
i
i
s
r
Rheology Solutions Instrument: HAAKE ViscoTester 550, HAAKE RotoVisco c m v
i r
e
r
u s
e
• l
e d r t
t
t
a
a u
s
i c s
r
r r
a t
n
m
e e
i r
x
t
f
d a
e
g a
o h
Industry Term: Yield Stress u
n r c
i m
w t e
t
s
e c x
f
s l
Definition: The minimum shear stress required to initiate flow in a fluid. r
e n
o a e
c
i
t e
s
r i
e
Governing Properties: Governed by the structural properties of the material at rest, measured by extrapolationw
r
e c
c
n
t e
s
e
i
r
n
a
using a flow curve, or using the vane technique, both on a CR or CS instrument.c It can
e m
e w
i
s
m t y
h
l c
t
f
also be measured using a CS rheometer by a stress ramp. s n
•
o
i
o
o p
s e
t
w
Rheology Solutions Instrument: HAAKE ViscoTester 550, HAAKE RotoVisco, HAAKE RheoStress, HAAKE MARS. e
e
h t •
c
s t
d
r
s
n
•
e
r
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t e
a o
c
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d g l
e
t
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o
n
h
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d
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c
n
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o n
Disclaimer d
t g a o
o
e r
f
n i
t
i
t d d
s n e a
•
i t n
s m i l
a
The information contained in this report is not intended for direct use as a tool for process development. It is a guide only. This a o r
e i
o n c
t
i t t r
a s t
a d
document remains the property of Rheology Solutions Pty Ltd, and may not be reproduced or altered in any way without the written• g y n s
r e i
s l o
o d n o permission of the owners. c r a C
t e n e g
Q c © Rheology Solutions Pty Ltd 2006 n i r o r
i l o v u t o r a c t a
c e a e s i e s r i c t i r e n v p d u p r t a o n e g a a m s r r • e e s t od s p e t l n Page© 2005 14 Rheology Solutions Pty Ltd (00) (4) [email protected]• e a n m a c s t i e e r s t v t o e r m s l i p e u • l a s r t a p s t r i u t d s o c s s e i n np l Tim’s Top Tips - Explanation and Evaluation of Mouthfeel
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