Rheological Aspects of Process Engineering in Food Manufacturing

Jay SellahewaResearch Group Leader, Process Engineering Science25 November 2009

Overview

• Consumer trends and the food manufacturing industry

• Process engineering in the food industry

• The role of rheology in food manufacturing

Pleasure(sensory

experience)

Pleasure(sensory

experience)

Environment(‘clean-green’)Environment(‘clean-green’)

Convenience(‘time factor’)Convenience(‘time factor’)

Price(good value)

Price(good value)

Health(‘well-being’)Health

(‘well-being’)Safety and

security (no

compromise!)

Safety and security

(no compromise!)

Individualism(‘tailored food’)Individualism(‘tailored food’)

FOOD MEGA- TRENDS

PresenterPresentation NotesThe main drivers in the global food industry at the moment include health, driven by a desire on the part of the consumer for greater control over their ‘well-being’ through food, convenience, driven by modern lifestyles, and of course pleasure, driven by a desire on the part of the consumer for a great sensory experience when they their food.

Both these main trends and the combination of these drivers generate opportunities for truly innovative and multidimensional products, in which for example a health-promoting product can also be pleasurable and/or convenient to eat. Development of such products will rely upon new multifunctional ingredients, and of course, clever processes and processing aids to manufacture these ingredients!

Snapshot of the food processing industry in Australia

• Total value - $34.8b (2005/06)

• Share of total manufacturing sector 20% (2005/06)

• Australia accounts for 2.6% of world food exports(world’s 13th largest food exporter)

• Australia’s main processed food exports• Beef (raw, frozen and chilled)• Wine• Dairy products• Sugar

Drivers to profitability in manufactured foods low margin, high volume

• Consumer acceptance

• New product opportunities

• Cost-savings

• Process and energy efficiencies

• Standards that can be cost-effectively met

• Inventory and logistics management

• Sustainable competitive advantages

• Confidentiality

• Brand loyalty

• Strong influence by the retailers

A typical food processing system

ProcessRawmaterials Product

• Increase throughput• Maximise yield• Minimise waste• Reduce costs• Assure product and process safety• Maintain product quality attributes• Maintain nutritional requirements• Sustainable processing

(reduce energy and water use)

$Increase theProfitability of theenterprise

Material transformation through unit operations

Raw materialsValue added

ingredients and foods of the desired

quality

Unit operations

Material transformation

Transport phenomenaHeat, mass and momentum transfer

• Physical functionality• Nutritional functionality• Sensory properties• Safety

Process / Product interactions

Process

Understanding the process / product interaction is critical for thedevelopment of innovative products and processes

Understanding thefundamental principles of

Process Physics,Engineering & Science

Scientific approachinstead of an

empirical approach

Enables industry to:• Develop innovativeproducts and processes

• Improve the performanceof existing processes

Product quality

Process Engineering Science capabilitySocial, economic and

environmentalbenefits

The role of food rheology in food manufacturing

• Why is rheology important in food manufacturing?

• Food rheology in process design, modelling, optimisation, control, product formulation, sensory science

• Measurement of rheological parameters in food- off line measurement- on line measurement

• Future trends

Types of foods

• Fluids

• Solids

• Pastes

• Slurries

• Emulsions

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Rheology and food

• Pouring ketchup from a bottle

• Spreading butter and other spreads on toast

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Rheology and food

• Depositing dough and creams from a nozzle to a container

• Stability of emulsions

• Clarity of juices

http://images.google.com/imgres?imgurl=http://www.sg2c.com/img/Photo%2520dosage.JPG&imgrefurl=http://www.sg2c.com/index_gb.html&usg=__luOcRrpttViEJtk-j5gIvwIrS_I=&h=220&w=278&sz=28&hl=en&start=7&tbnid=jyV99FN7HiC-iM:&tbnh=90&tbnw=114&prev=/images%3Fq%3Ddepositing%2Bdough%26gbv%3D2%26hl%3Den

Rheology and food

• Enrobing chocolates

http://images.google.com/imgres?imgurl=http://everythingaboutfood.net/wp-content/uploads/2009/10/chocolates.jpg&imgrefurl=http://everythingaboutfood.net/tag/chocolate&usg=__IU536Ze-H1fXeqcU-egTa1EM19w=&h=300&w=300&sz=24&hl=en&start=5&tbnid=e2S_RGkzAeCt8M:&tbnh=116&tbnw=116&prev=/images%3Fq%3Dchocolates%2Bpictures%26gbv%3D2%26hl%3Denhttp://www.israelity.com/wp-content/uploads/2006/10/CHOCOLATES.jpg

Rheology and food

• Pouring honey

• Eating food

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Importance of food rheology

• Process design• Sizing pumps, heat exchangers, mixing vessels

• Process optimisation• Minimising waste• Maximising throughput

• Process control• E.g. – impact of the viscosity of milk concentrate on spray drying • Traditionally, process control in the food industry is an ‘art’ because of the

difficulty of quantitatively measuring product quality• The food industry relies on experienced operators to make decisions (e.g.

master bakers and cheese makers), end point detection

• Quality control• Quality control is difficult because of lack of instruments to measure product

quality on-line me

Importance of food rheology

• Product formulation• Understanding of food rheology is important in formulating

products

• Understanding product structure / texture and other sensory properties

• Rheology in the mouth• Tribology• Designing foods to the elderly who find it difficult to chew and

swallow• Dough rheology

• Stability of foods• Stability of emulsions

Typical Shear Rates for Food OperationsSource: Chemical Engineering for the Food Industry; Fryer et al

Operation Shear Rate (s-1) Examples

Settling of suspensions 10-6 - 10-4 Salad DressingsDraining under gravity 10-1 - 10 Vegetable oilsExtrusion 10 - 100 Snack Foods, CerealsPipe Flow 10 - 1000 Chocolate, SaucesChewing and Swallowing 10 - 100 Most FoodstuffsMixing or stirring 10 -1000 Fruit squashesSpreading 10 - 104 Margarine, butter

Measurement of rheological properties of foods

• Food rheology is complex. Most foods are:• Non uniform• Heterogeneous• Non Newtonian (mostly pseudoplastic – shear thinning)• Viscoelastic• Difficult to characterise• Difficult to measure rheological properties

Instruments used for the measurement of rheological properties of foods

Rapid Visco Analyser (RVA)

An example - extrusion

• Moisture content• Particle size distribution• Protein content• Water absorption

• Screw speed• Water feed rate• Powder feed rate• Melt temperature• Barrel temp profile

Raw material properties Process variables Product quality attributes

• Colour• Texture• Bulk density• Rehydration properties• Flavour• Nutritional properties

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Melt rheology and product expansion

Steam

Melt rheology

Die

Die swell (viscoelasticity)Expansion

Product Structure affects texture

Degree of Cook

LowLow Degree of CookDegree of Cook HighHigh

Native crystalline granulesGelatinised granulesDamaged granulesStarch dispersedStarch degraded

((From Guy and Horne 1988)From Guy and Horne 1988)

Degree of cook

Measurement of Degree of cook - StarchMeasurement of Degree of cook Measurement of Degree of cook -- StarchStarch

• Gelatinisation• Polarised light microscopy• X ray crystallography• DSC• Enzymic methods

• Molecular breakdown• Viscometric methods• MS chromatography

Degree of Cook (DOC) Measurement(Guy and Horne (1988))

ηapp = Kγ (n-1)

KK

nn

RVA Viscosity curve

0 5 10 15Time (min)

0

100

200

300Vi

scos

ity (R

VU)

Pasting Temp.

PeakTime

PeakVisc.

Setback

HoldingStrength

Break-down

FinalVisc.

0

40

80

120

Tem

pera

ture

(C)

RVA Pasting Curve (Guy and Horne (1988)RVA Pasting Curve (Guy and Horne (1988)

0 4 8 12Time (min)

0

1000

2000

3000

4000

5000Vi

sco s

ity(c

P)

1 min 4 min

7.6 min 12 min

(x 400)

Dynamic Mechanical Analyser (DMA)

Enables the measurement of glass transition temperature, loss modulus and storage modulus of food stuffs

DMA of pregelatinised waxy maize starch (wms)

Drop log E’slope

Tan δ peak

Temperature (°C)

Log

E’(P

a)Tan δ

50 100

9.0

7.5 0

0.5

α

Pregelatinised wms powder, hydrated 20-25% (w/w), pressed (20 tons, 90-100°C, 5-10 min), re-equilibrated in at room temperature different RH enviroments. RH=43% for sample shown. (Kalichevsky et al.,1992).

E’ Storage ModulusE” Loss Modulus

Tan δ

= E” / E

Effect of water content on the Tg of waxy maize starch(Aung Htoon, CSIRO)

0

0.2

0.4

0.6

0.8

-40 0 40 80 120

Temperature (° C)

97

92

8575

4365

tan

δ

DMA thermograms (tan δ) of pregelatinised wms at different RH

(%) Effect of water content on the Tg of pregelatinised wms

0

40

80

120

5 10 15 20 25 30

water content % (w/w wb)

Tg (°

C)

log E’

tan δ

DSC midpoint

Paar Physica MCR301

Mechanical shear (Blending)

Particle clusters (~230 µm)

Single cells (~70-80 µm)

Cooking(100°C, 10 min)

Scale = 775 µm × 775 µm

Plant cell wall microstructure (Leif Lundin, CSIRO)

Cell fragment (~32 µm)

Particle clusters (~200 µm)

Blanching(80°C, 10 min)

Raw material

PresenterPresentation NotesBack to 2D level, using carrot tissue as an example, Particle solids v.s. total solids

The questions:Do they have same behaviour, interaction

How to predict their functional properties from known structure, or can we?

Bare in mind that they are soft, deformable particles,

It is challenging to take the measurement

Rheology of soft elastic particles (Leif Lundin, CSIRO)

0

100

200

300

400

500

600

700

0 1 2 3 4 5 6

Total solids (%)

Sto

rage

mod

ulus

G' (

Pa)

5%

1.5%

3.5%

1%

2%

3% Clusters of cells

Individual cells

Strain 0.1%Frequency 0.1Hz

2x10-1 100 10110-1

100

101

102

103

II

I

III

G' (

Pa)

Total solid (%)

⎥⎥⎦

⎤

⎢⎢⎣

⎡⎟⎟⎠

⎞⎜⎜⎝

⎛−=

3/1

1'φφcAG

PresenterPresentation NotesElastic particle dispersions

Sliding speed mm/s

1 10 100 1000

Fric

tion

fact

or

0.01

0.1

1

Dry water 50% Glc Syrup Canola oil

Effects of altering solvent properties(Leif Lundin, CSIRO)

• Stribeck curve delineates three main regions: Boundary, mixed, and hydrodynamic• Start of lubrication by water (entry to mixed) indicated by divergence from dry contact • Water begins to lubricate from ~ 10mm/s but probably does not enter hydrodynamic regime• Oil lubricates from < 0.05 mm/s enters hydrodynamic regime from ~ 100mm/s• Increasing viscosity of aqueous system enhances low speed lubrication• Effects due to surface (hydrophobic / hydrophillic ) properties

1 10 100 1000

Fric

tion

fact

or

0.01

0.1

Generic ‘master curve’ for aqueous based samples(Leif Lundin, CSIRO)

Low speed, hard contact region Modified ↑↓

by solvent properties

– fat, surface tension etc

Onset of mixed lubrication modified up or down speed and friction axes depending on particles and viscosity

High speed frictionmodified by particlesand viscosity

Plasticity?Rigidity?Strength?

Information from speeds below ~0.5 mm/s unreliable, but contributes to ‘shear history’

Critical viscosity is high shear

Onset of Hydrodynamic lubrication modified up or down speed and friction axes depending on particles and viscosity

Capillary Rheometer (twin bore)

Temperature sensorPressure transducer

Die

• Small scale prediction of the correct appearance, texture and processibility of cereals• Experimental design to understand the effect of processing on temperature, pressure,

shear, moisture, etc on product quality

Confocal Microscopy

On-line measurement of rheology

• No accurate instruments for on-line measurement of food rheology

• Oscillating blade• Difficult to correlate instrument readings with product quality

and traditional measurement of product quality (e.g. Bostwick instrument for tomato paste)

http://images.google.com/imgres?imgurl=http://www.christison.co.uk/food/images/bostwick.jpg&imgrefurl=http://www.christison.co.uk/food/bostwick.html&usg=__gWyGsYHLD17t9aDkiCr6S-rMado=&h=225&w=300&sz=65&hl=en&start=1&tbnid=aW_bmDaBtOExlM:&tbnh=87&tbnw=116&prev=/images%3Fq%3Dbostwick%2Binstrument%2Bfor%2Btomato%2Bpaste%26gbv%3D2%26hl%3Den%26sa%3DGhttp://img.ecplaza.com/my/rock185558/4.jpghttp://images.google.com/imgres?imgurl=http://www.made-in-china.com/image/2f0j00VMbQdIvUYfplM/Tomato-Paste-SHZ-02-.jpg&imgrefurl=http://www.made-in-china.com/showroom/rock1855/product-detailIeWxwPoAafrH/China-Tomato-Paste-SHZ-02-.html&usg=__9CWerJ-q4hvtt_dP1f10TQPFwfg=&h=375&w=500&sz=70&hl=en&start=3&tbnid=-SuI_3o_TR5H9M:&tbnh=98&tbnw=130&prev=/images%3Fq%3Dbostwick%2Binstrument%2Bfor%2Btomato%2Bpaste%26gbv%3D2%26hl%3Den%26sa%3DG

Future trends

• Better characterisation of foodstuffs through a deeper understanding of rheology

• Development of food rheology databases

• Using rheological data in process modelling (lack of data is a major limitation at the moment)

• Correlation of rheological data with product quality attributes (including sensory attributes)

• Optimal design of processing conditions and formulations

• Process control and quality control through the development of on-line rheometers

Groups active in food rheology

• Australia• CSIRO (Sumana Bell, Leif Lundin, Jay Sellahewa)• University of Queensland (Jason Stokes)• University of Melbourne (David Boger)• University of NSW (Janet Paterson)

• Overseas• Michigan State University (James Steffe)• Purdue University (Osvaldo Campanella)

Contact UsPhone: 1300 363 400 or +61 3 9545 2176

Email: enquiries@csiro.au Web: www.csiro.au

Thank you

CSIRO Food and Nutritional SciencesJay SellahewaResearch Group Leader, Process Engineering Science

Phone: 02 9490 8383Email: jay.sellahewa@csiro.auWeb: www.csiro.au

Rheological Aspects of Process Engineering in Food Manufacturing�OverviewFOOD MEGA-�TRENDSSnapshot of the food processing industry in AustraliaDrivers to profitability in manufactured foods� low margin, high volumeA typical food processing systemMaterial transformationProcess / Product interactionsThe role of food rheology in food manufacturingTypes of foodsRheology and foodRheology and foodRheology and foodRheology and foodImportance of food rheologyImportance of food rheologySlide Number 17Measurement of rheological properties of foodsInstruments used for the measurement of rheological properties of foodsAn example - extrusionMelt rheology and product expansionProduct Structure affects textureDegree of cookMeasurement of Degree of cook - StarchSlide Number 25RVA Viscosity curveSlide Number 27Slide Number 28Slide Number 29Slide Number 30Slide Number 31Plant cell wall microstructure �(Leif Lundin, CSIRO)Rheology of soft elastic particles�(Leif Lundin, CSIRO)Slide Number 34Slide Number 35Slide Number 36Confocal MicroscopyOn-line measurement of rheologyFuture trendsGroups active in food rheologyThank you