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