Ingredient Functionality &

Characterization

David Julian McClements

Biopolymers and Colloids Laboratory

Department of Food Science

• Emulsifiers

• Texture Modifiers

– Thickening Agents

– Gelling Agents

• Weighting Agents

Emulsifiers:Major Functions in Food Emulsions

Functional Properties• Emulsion Formation

• Emulsion Stabilization

• Modification of Interfacial Properties

• Modification of Crystallization

• Interaction with Biopolymers

Displacement –

ice cream manufacture

Crystal modification –

margarine manufacture

Polymer interaction –

Bread manufacture

Emulsifiers: Formation

Emulsifier Factors Affecting Formation:• Concentration and Surface Load

– sufficient present to cover all surfaces formed

• Adsorption Kinetics – adsorbs fast enough to form protective coating

• Interfacial Tension– lower γ gives smaller droplets

• Protective Coating– Emulsifier layer should protect against aggregation

−−

− − − −− − −− − −

Movement

to surface

Incorporation

In surface

Film

Formation

Microfluidics

Emulsifiers: Stability

+ + + +

Charge

Thickness

Hydrophobicity

Emulsifier Factors Affecting Stability:

• Colloidal Interactions- Interfacial Thickness, Charge & Hydrophobicity

• Resistance of membrane to disruption- Interfacial rheology

Environmental

Responsiveness:

pH, I, T

Common Food Emulsifiers

Small Molecule Surfactants– Tweens, Spans, fatty acids, DATEM

– Sucrose esters, polyglycerol esters, monoglycerides

Phospholipids– Egg, soybean, milk

Biopolymers– whey, casein, egg, gelatin, soy

– modified starch, gum arabic, modified cellulose

− − − −

−

−−

− −

Emulsifier Applications in Foods

Salad Dressings

– Tweens

– PGA

– Proteins

Milk & Cream

– Proteins

– Phospholipids

Mayonnaise

– Proteins

– Phospholipids

– Yolk particles

Nutritional Beverages

– Proteins

– Phospholipids

Soft Drinks

– Gum Arabic

– Modified Starch

Ice Cream

– Proteins

– Phospholipids

– (Surfactants)Sauces & Dips

– Mono/diglycerides

Specifying Emulsifier FunctionalityChoosing the most appropriate emulsifier

Physicochemical Factors• Emulsion type (O/W or W/O)

• Minimum amount needed (Cmin)

• Minimum droplet size achievable (rmin)

• Ingredient compatibility

• Sensitivity to environmental stresses (pH, I, T)

Practical Factors• Ease of utilization

• Reliability/Consistency of source

• Long term stability

• Sensory properties

Economic & Marketing Factors• Cost

• Label friendliness

Currently no

standard method of

specifying

emulsifier

functionality

Surfactants:

Molecular Structure

Head Group• Electrical charge (non-ionic/ionic)

• Chemical groups

• Length and cross-section

Tail Group• Number of chains

• Length of chains

• Saturation of chains

+−

− − −

Industrial Manufacture of Surfactants

Danisco

Commercial surfactants are

actually a complex mixture of

many different molecules

Tween 20 Structure: ChemBlink

MicelleReverse

Micelle

Vesicle

Non-spherical

Micelle

Self Assembly of Surfactants

Surfactants can form a variety of structures, with different

functional properties, depending on their molecular structure

Classification of Surfactants

• Bancroft rule

– The phase in which the surfactant is most

soluble (dispersible) forms the continuous

phase of emulsion

• HLB number

– The ability of a surfactant to stabilize an

emulsion depends on balance of hydrophilic to

lipophilic groups

HLB Classification Scheme

0.475-CH3

0.475-CH2 -

0.475-CH-

Group

Number

Hydrophobic

Group

HLB = 7 + Σ(hydrophilic groups) - Σ(lipophilic groups)

CH3(CH2)11-O-S-O− Na+

O

O

6.8Sorbitan ring

2.1-COOH

21.2-COO−H+

38.7-SO4−Na+

Group

Number

Hydrophilic

Group

HLB Numbers of Some Food

Surfactants

Surfactant Name HLB Number

Sodium lauryl sulfate 40

Potassium Oleate 20

Tween 20 15

Decaglycerol monooleate 14

Ethoxylated monoglyceride 13

DATEM 8

Soy lecithin 8

Calcium stearoyl lactylate 5.1

Glycerol monoleate 3.4

Sorbitan trioleate 1.8

Oleic acid 1.0

Hydrophilic

Lipophilic

Oleic acid

Tween 20

HLB Classification Scheme

HLB Number Solubility Emulsion Type

Very Low (<3) Oil Unstable

Low (3-6) Oil W/O

Medium (6-8) Oil&Water Unstable

High (8-18) Water O/W

Very High (>18) Water Unstable

Benefits and Limitations of

Classification Schemes

Benefits• Provide information on emulsion type (O/W or W/O)

• Enable rational selection of mixed surfactant systems

Limitations• Not applicable to biopolymers

• No insight into: • Minimum droplet size that can be created

• Amount of emulsifier needed

• Stability of emulsion to environmental stresses

Testing Emulsifier Efficiency:Fundamental Measurements

• Surface Load (ΓΓΓΓ)– mg/m2

– Maximum surface area that can be covered per gram

• Binding Affinity (c1/2)– Amount of emulsifier required to reach saturation

• Maximum Surface Pressure (ΠΠΠΠSat)– mN/m

– Minimum droplet size achievable

• Adsorption Kinetics− ∆ci/δt (measured under dynamic conditions)

– Minimum droplet size achievable0

5

10

15

20

25

30

35

40

0.0001 0.01 1

[Emulsifier]

ΠΠ ΠΠ (

mJ

/m2)

π∞

c1/2

www.dataphysics.de

0

1

2

3

4

5

0 2 4 6 8 10

Emulsifier Concentration (wt%)

Mea

n R

ad

ius

( µµ µµm

)

Depends on:

• Solution Conditions

• Mechanical Device

Cmin

rmin

Testing Emulsifier Efficiency:Practical Tests for Emulsion Formation

Cmin = minimum amount of

emulsifier to homogenize fixed

quantity of oil

rmin = minimum achievable

droplet size

Factors Affecting Emulsion

Formation

Cmin & rmin Depend on: • Adsorption Rate

• Interfacial Tension Reduction

• Packing Efficiency

• Membrane Protective Effect

High Cmin Low Cmin

Testing Emulsifier EfficiencyPractical Tests for Emulsion Stability

Emulsion

preparation

Emulsion

characterization

• Droplet Size

• Droplet charge

• Rheology

• Creaming

Long term storage, accelerated or environmental stress tests

or

Test

Initial

Emulsion

Minerals and pH

• pH 2 to 8

• NaCl 0 – 1 M, CaCl2 0 – 100 mM

Thermal Processing

• 30-90 ºC for 30 minutes

Freeze Thaw Cycling

-20ºC / +20ºC

Dehydration

• Spray drying or Freeze drying

Mechanical Agitation

• Shaking, Stirring

Testing Emulsifier EfficiencyStability to Environmental Stress

Stable Unstable

Stability to Environmental Stress Influence of Emulsifier Type

--

-

-

-

-

-

-

--

-

--

-

-

-

-

-

-

--

-

Steric, (Electrostatic)

Electrostatic, Steric

Steric, Electrostatic

Electrostatic, Steric

Stabilizing

Mechanism

T

pH, I, T

-

pH, I, T

Environmental

Sensitivity

Surfactants

• Non-ionic

• Ionic

Polysaccharides

Proteins

Emulsifier Type

• Thickness

• Charge

• Hydrophobicity

• Rigidity

0

1

2

3

4

5

6

3 4 5 6 7

pH

Mea

n D

iam

eter

( µµ µµm

)

WPI

GA

MS

Stability to Environmental Stress Influence of Emulsifier Type

WPI stabilized emulsions are sensitive to pH, minerals, temperature

Comparison of Physiochemical

Properties of Emulsifiers

The choice of an appropriate emulsifier depends on many factors

(Freezing, Drying)HighHighSlowYes

(No)

Polysaccharide

Freezing, Drying

Heating, I, pH

Low /

Medium

MediumMediumYesProtein

Freezing, Drying

Heating, I

LowLowRapidNo

(Yes)

Surfactant

- Ionic

Freezing, Drying

Heating

LowLowRapidNoSurfactant

- Non-ionic

Environmental

Sensitivity

Amount

Needed

Interfacial

Tension

Adsorption

Rate

NaturalEmulsifier

Type

Selecting an Emulsifier

• Establish Operating Environment

– pH, I, T, Mechanical stress, Water content

• Establish Labeling Requirements

– Natural? Kosher? Vegan? GMO? etc

• Establish Maximum Cost-in-Use of Emulsifier

• Identify Available Emulsifiers

– Surfactants, Phospholipids, Biopolymers

• Carry Out Product Tests

– Particle Size, Amount Needed, Stability, Ease of Use

Texture Modifiers

Functional Properties:

• Texture – Modify the overall textural properties

and mouthfeel of the system

• Stability – Retard movement of droplets and other

particulate matter

Mode of Operation:

• Thickening Agents: – increase viscosity because of

their large molecular dimensions

• Gelling Agents – form gels because of their ability

to form intermolecular cross-links−−−−S−−−−S−−−−

Thickening & Gelling Agents

Typical Food Ingredients

Polysaccharides

– Agar, Alginic acid, Alginate, Carrageenan, Guar

gum, Gellan gum, Curdlan, Modified Celluloses,

Modified starches, Pectins, Xanthan

Proteins

– Gelatin, Whey, Casein, Soy, Egg

Sugars & Polyols

– Glycerol, Sorbitol, Lactitol, Mannitol

– Trehalose

Xanthan Gum: IFR, UK

Thickening AgentsMolecular Characteristics

Charge Density

++

+

+

+ +++

Low High

Molecular Weight

HighLow

Charge Sign

+

+

+ +++

Negative Positive

−−−−

−−−−

−−−− −−−−−−−−−−−−

Unbranched Branched

Branching

Conformation

Random Coil Globular Rigid Rod

Biopolymer Solution RheologyInfluence of Particle Concentration

• Biopolymers Increase Fluid Viscosity

No Biopolymer

BiopolymerGreater

Energy

Dissipation

η = η0 (1 + 2.5 φ)

Thickening AgentsQuantifying their Functionality

Rotating

Polymer

Trapped

Water

polymer

sphere

VV

VR =

Volume Ratio:Factors Influencing RV:

• Molecular Weight

• Degree of Branching

• Electrical Charge Density

• Conformation

• Interactions

η = η0 (1 + 2.5 Rvφ)

1

10

0.01 0.1 1 10

Concentration (kg m-3

)

Rela

tiv

e V

isco

sity

Thickening Agents

Influence on Solution Rheology

Dilute

c*

Semi-Dilute

Concentrated

c* ≈ 530 / Rv (kg m-3)

1

10

0.01 0.1 1 10 100

Concentration (kg m-3

)

Rela

tive V

iscosi

ty

1

100

1000

5000

Rv

Thickening Agents

Influence of Structure on Rheology

4469383Gelatin

8101270345Collagen

2.33.668Hemoglobin

1.72.714.1Lysozyme

RV[η][η][η][η]

(g/mL)

MW

(kDa)

Proteins

* Adapted from Peter Wolf (2005)

Thickening Agents: Effective Volumes

Rv ≈ 0.64 × [η] (in g mL-1)η

C

Thickening Agents: Effective Volumes

7011050Pectin

124

500

1540

193

780

2,400

100

300

1,000

Xanthan

64

157

99

245

500

1,000

Amylose

45

109

71

170

100

300

LBG

40

77

62

120

100

200

Guar

173

350

270

550

100

300

Alginate

RV[η][η][η][η]

(g/mL)

MW

(kDa)

Polysaccharides

* Adapted from Peter Wolf (2005)

Thickening AgentsInfluence of Molecular Properties on RV

Effect of Branching

Branched:

Low RV

Linear:

High RV

Effect of Salt (Charged Polymer)

−

−−

−

Low Salt:

High RV

High Salt:

Low RV

−−−

−++

++

Effect of Chain Length

High MW:

High RV

Low MW:

Low RV

0.001

0.01

0.1

0.001 0.01 0.1 1 10 100 1000

Shear Stress (Pa)

Vis

co

sity

Thickening Agents

Shear Thinning Behavior

• Entangled

• Extended

• Elongated

• Aligned

Less resistance

to flow

More resistance

to flow

Decreasing

Concentration

Gelling Agents: Molecular Basis of Functionality

Why do some biopolymers form gels?

What determines gel characteristics?

Eggs• Globular Proteins

• Heat-set

• Irreversible

Gell-O• Flexible Proteins

• Cold-set

• Reversible

Pudding• Starch

• Cold/Heat-set

• Irreversible

Food Gels: Many Different Gel Mechanisms

Deserts• Polysaccharides

• Ca2+-set

• Irreversible

Molecular Basis of Gelation

Molecular

Characteristics:

- MW, Conformation,

Flexibility, Charge

Physical Properties:

- Texture, Appearance,

Stability,

Mouthfeel

Microscopic behavior:

- Interactions,

Organization

Design

Understanding

Hydrogen

bondingHydrophobic

attraction

Ca2+−−−−COO−−−− −−−−OOC−−−−

Salt

bridgeCovalent

bond

VDW

attraction

Gelling Agents: Gelation Mechanism

−−−−S−−−−S−−−−

Particulate gel Filament gel

Gel Structure and Properties

• Gel Strength

• Gel Appearance

• Water Holding Capacity

• Reversibility

• Setting Mechanism

– Heat, Cold, Ions, pH etc

• Environmental Responsiveness

Key Properties:

Pore

Size

Bond

strength

Structural-unit

dimensions

Bond

number

Thickening & Gelling AgentsSelection Criteria

Physicochemical Characteristics

– Rheology: Viscosity Enhancement Capacity; Gel

strength, Gelation Temperature, Reversibility, etc

– Dispersion & Solubility Characteristics

– Appearance (Transparent, Turbid, Opaque)

– Environmental Sensitivity (pH, T, I)

– Ingredient Compatibility

Other Characteristics

– Legal Status

– Label Friendliness

– Cost, Reliability of Supply

Weighting Agents: Retardation of Creaming

VV = = --22rr22∆ρ∆ρg/9g/9ηη11

Stokes Law:Stokes Law:

Role of weighting agentsRole of weighting agents::

•• Incorporation of dense oilIncorporation of dense oil--soluble material in the oil soluble material in the oil

phase reduces the density difference (phase reduces the density difference (∆ρ∆ρ), thereby ), thereby

slowing gravitational separation.slowing gravitational separation.

Weighting AgentsCreaming Velocity of Oil Droplets

-0.5

-0.3

-0.1

0.1

0.3

0.5

-100 0 100 200

∆ρ∆ρ∆ρ∆ρ (kg m-3

)

U/r

2 x

10

6 (

m-1

s-1) Stable to Creaming

Sedimentation

Creaming

Commonly Used Weighting

Agents

Name Density Characteristics

BVO 1290 kg m-3 Viscous Liquid

SAIB 1150 kg m-3 Viscous Liquid

Ester Gum 1080 kg m-3 Solid

Damar Gum 1060 kg m-3 Viscous Liquid

Factors: Legal Limits, Ease of Utilization, Labeling, Reliability

SAIB: sucrose acetate isobutyrate

BVO: brominated vegetable oil

Weighting Agent ContentWeighting Agent Content: : φφWAWA = [= [ρρAQAQ -- ρρOO]/ []/ [ρρWAWA -- ρρOO]]

Alternative Strategies to

Traditional Weighting Agents

Filled

Hydrogel Particles

Make density of particle equal density of surrounding aqueous phase:

• Density of oil < density of water

• Density of biopolymers > density of water

• Density of solid fat > density of liquid oil

Solid Lipid

Nanoparticles

Multilayer

Emulsions

Importance of Ingredient

Interactions

Functional ingredients can interact with other components,

which can either improve and adversely affect their

performance

Interactions Change:

• Charge

• Conformation

• Hydrophobicity

• Solubility

• Association

Interactions: Electrostatic,

Hydrophobic, Hydrogen bonding

0

5

10

15

0 0.05 0.1 0.15 0.2 0.25

[Pectin] (wt%)

d3

2 (

µµ µµm

) −

−

−

Example of Ingredient Interactions:Emulsifier and Thickening Agent

Emulsifier: ββββ-Lg

Thickening Agent: Pectin

++++

++++

++++++++

++++++++

pH 3

Importance of Order of Ingredient

Incorporation

The order of ingredient addition may have a large

impact on product properties:

• Homogenization - viscosity, competitive adsorption

• Thermal Processing - thermally labile substances

• Ingredient interactions - pH, salt, surfactants, chelating agents

Example of Importance of Order of

Ingredient Addition:

NaCl Addition &Thermal Stability

0.1

1

10

100

30 50 70 90

Temperature (oC)

Dia

met

er (

µµ µµm

)

Heat + 0mM

0 mM + Heat

Heat + 150mM

150 mM + Heat

Surface

Denaturation

Thermal

Denaturation

Thermal stability of β-Lg stabilized O/W emulsions (pH 7)

Wrap Up

• Clearly establish functional characteristics

of each component in product

- Why is it there?

- What role(s) does it play?

- Is there a better alternative?

- Is there a cheaper alternative?

- Is there synergism/antagonism?

Water0-25172.840E 433Polysorbate 80Polyoxyethylene (20) sorbitan

monooleate

Water0-25172.838E 436Polysorbate 65Polyoxyethylene (20) sorbitan

tristearate

Water0-25172.836E 435Polysorbate 60Polyoxyethylene (20) sorbitan

monostearate

Oil0-15-E 492STSSorbitan tristearate

Water0-25172.842E 491SMSSorbitan monostearate

Oil/Water* 0-10172.859E 473Sucrose esters of FA

Oil 0-25172.856E 477PGMSPropylene glycol esters of FA

Water 0-25172.854E 475PGEPolyglycerol esters of FA

-172.830-SMGSuccinic acid esters of MG

Oil NL172.852E 472bLACTEMLactic acid esters of MG

OilNL172.828E 472aACETEMAcetic acid esters of MG

OilNL184.1505E 471MGMonoglycerides

NON-IONIC

Water0-50184.1101E 472eDATEMDiacetyl tartatric acid esters of MG

WaterNL172.832E 472cCITREMCitric acid esters of MG

Oil0-20172.844E 482CSLCalcium stearoyl lactylate

Water0-20172.846E 481SSLSodium stearoyl lactylate

Oil/waterNL172.863E 470FAFatty acid salts

Oil/waterNL184.1400E 322−Lecithin

IONIC

SolubilityADI (mg/kg)US FDAEU numberAbbreviationChemical Name

Food Grade Surfactants