Proteins – Functionality & Application
Anneke Martin
Content
Functionality
Techno-functionality of proteins
Interfacial properties
Gelation properties
Type of protein networks
Water holding
Texturizing of proteins
Available methods
Extrusion
Industrial examples
Three areas of functionality
Physiological functionalityPhysiological functionality Nutritional functionalityNutritional functionality
Physical functionalityPhysical functionality
…protein
structure & conformation
proteinstructure &
conformation
Types of proteins – based on structure/shape
Globular proteins
(e.g. b-lactoglobulin, soy protein)
Fibrillar proteins
(e.g. gelatin, meat)
Random coil proteins
(e.g. caseins)
Other proteins (macropolymers)
(e.g. gluten)
Different classes of ingredient functionality
Functionality Property Example
Techno-functional SolubilitySolubility
Precipitation
Bulk rheologyThickening
GellingTexturizing
Surface activityFoaming
Emulsifying
Sensory Binding of lipids/flavors
Bio-functional NutritionalDigestibilityAllergenicity
Anti-microbial
PhysiologicalACE inhibition
Opoid activity, etc.
Techno-functional properties of proteins
Function Mechanism Food
solubility hydrophilicity beverages
viscosity water bindinghydrodynamic size
soups, gravies, dressings
water binding hydrogen bonding meat/sausages, cakes, breads
gelation network formation meats, sausages, pasta, baked goods
elasticity hydrophobic interactionsdisulfide crosslinks
meat products, bakery products
emulsification interfacial adsorptionfilm formation
sausages, soups, dressings, desserts
foaming interfacial adsorptionfilm formation
whipped toppings, cakes, mousse, nougat
fat and flavor binding hydrophobic bonding bakery products
Solubility
0 M NaCl
0.5 M
0.2 M
Renkema et al.
β-lactoglobulin
Franco et al. (2011) Fluid Phase Equil 306:242
[NaCl]
0.02
0.01
0.005
0.001
soy protein
Changes in solubility
Insolubility arises from aggregation which is caused by:
Heat (unfolding � exposure hydrophobic groups � more attraction)
Change in pH (at iso-electric point no net charge � no repulsion)
Enzymatic hydrolysis (exposure of hydrophobic groups � more attraction)
Association with non-protein compounds (lipids, flavors, polysaccharides)
NB Presence of salts is needed to solubilise meat proteins!
Interfacial properties of proteins
Most proteins have hydrophilic and hydrophobic parts
Protein unfolds at interface and decreases interfacial tension
Due to charge proteins act as stabiliser at the air/water and oil/water
interface
air
fat
----
--
---
--
-
--
� Negative charge causes electrostatic repulsion and stabilizing effect
� Addition of salts (e.g. Na+) decreases repulsion
Interfacial properties of proteins
Interface, role of protein
Steric repulsion/charge
Effect of e.g. salt, pH for stability
Destabilisation process
Practical example
Examples of foods with interfaces
solid liquid gas
solidsolid suspension: fruit ice, chocolate
solid emulsion, gel:jellies, cheese, processed meat
products
solid foam: foam candy, bread,
baked products
liquid sol, suspension:
orange juice, acidic beverages
emulsion: milk, mayonnaise, margarine, french
dressing
foam: meringues, whipped cream, beer foam
gas aerosol aerosol
DISPERSED PHASE
CO
NT
INU
OU
SP
HA
SE
Sausage emulsion – comminuted meat
Contains ~30% fat present in small droplets
Stable homogeneously distributed fat droplets are positive for
juiciness & tenderness
Gelation properties (globular proteins)
Heat treatment � unfolding � aggregation � gelation
Gelation kinetics, type of gel and gel strength are a.o. influenced by:- temperature-time- pH- presence of salts- protein concentration
NOT every protein denatures and forms gels!
Gelation properties
gelatin
whey protein
soy protein
MOLECULARDENATURATION/AGGREGATION
GELATION NETWORK
Mechanisms of network formation
Heat-induced gels
High Temperature (whey, soy, egg white)
Low temperature (gelatin)
Cold -set gels, pre-heat treatment followed by:
Acidification (yoghurt)
Enzyme induced, e.g. rennet (cheese)
Addition of salts, e.g. Ca2+ (tofu)
High pressure induced
Combination of pressure and temperature
Type of network:• fine/coarse
stranded• particledetermines rheological and eating properties
Methods: from molecule to food product
Chromatography
Thermal analysis
Circular dichroism
SDS Page
< 10 nm 20-500 nm 1-500 µm mm-cm >mm-cm
Information on: -structure-unfolding vs. native-denaturation temp.
Light scattering
Electron microscopy
Information on: -aggregation-size of structures
Confocal microscopy
Light microscopy
Rheology
Information on: -size of structures-properties of network at small deformation-ingredient interaction
Texture analyzer
Microscopy
Texture analyzer
Sensory panel
Information on: -properties of network at large deformation related to eating properties-microstructure
Information on: -properties of network at large deformation-sensory properties, liking
Typical methods
Texture Analyzer – large deformation – eating properties
Rheometer – small deformation – gelation kinetics
Recoverable energy is high for elastic materials
Rheological properties protein networks
Link to hardness, elasticity
Structure (particle versus stranded network) versus water binding
Short chains versus long chains (winegum, young versus old cheese)
Typical methods
TA
Rheometer
Microscopy
Light scattering
Egg white protein – ovalbumin
Parameter
[NaCl] 0.2 M -
Type gel particle stranded
Fracture stress (kPa) 70 37
RE (%) 45 75
TIFN 2013
Vegetarian burger (Javaanse schijf)
Role of egg white protein: binding water and holding mass together
Texture analyzer and sensory panel are used to determine differences
TNO 2013
Soy protein – effect of salt type
Aggregates with Ca > Mg
Coarseness gels MgCl2 >MgSO4
Both anion and cation determine
structure of protein network
Effect on water holding, hardness & eating
properties
Urbonaite (2013) TIFN
Water binding/holdingRelevant for juiciness, tenderness
Water holding capacity in meatWater holding capacity in meat proteins
[NaCl] ↑
plasma
[gelatin]
TIFN 2013 TNO 2010
Texture analyzer: hardness, elasticity, serum release
Serum release during deformation is a measure for
juiciness and flavour perception
The perceived juiciness is the result of the amount of
serum that is pushed out of the meat matrix while
chewing and the ability of the tissue to bind water , which
is affected by the salt content.
Eating properties
Sausages with high serum release were perceived significantly saltier than
those with little serum release
Sausages with a high serum release were perceived more juicy than those
with a low serum release.
interconnected pores
separate pores
protein continuous system
Microstructure controls serum release � Serum release relates positively to salt/flavour perception
vdBerg (2007) Food Hydrocoll 21:961
Gluten
80% of gluten consists of gliadin and glutenin
Gluten are not soluble in water
Gives structure to e.g. bread and pasta
Forms strong reversible elastic network and entraps air bubbles
during proving and baking
Glutenfree
Gliadin fraction is said to be responsible for coeliakie
Replacement of gluten by hydrocolloids in bread does not result in
satisfying products
Gliadin fractions can be replaced by protein particles made from whey
protein or gelatin
protein particles flour+water+protein
Van Riemsdijk et al. (2011) J Cereal Sci
Replacement of meat proteins by plant protein
Meat protein – fibrillar structure
Plant proteins – globular or other protein
unfolding of globular proteins and alignment of protein aggregates into fibrillar structures
TUNE FUNCTIONALITY OF PROTEIN !
Structuring of proteins
Formation of fibrillar-like structures of protein to mimic meat
Electrospinning
Shear cell
Fibril formation at low pH
Extrusion
Examples: Valess, Ojah (Beeter), texturized protein (Solae)
Electrospinning
Spinning of proteins in food-grade way is difficult
For use in food fibers need to be collected and/or
aligned (in progress)
Upscaling of process needs attention
Nieuwland et al. 2013 TNO
gelatin + 15% WPI + 12.5% WPI + 10% WPI
Shear cell
Flow induced structuring of 30% caseinate in
combination with enzymatic crosslinking
Fibrous structures of µm-mm
Manski et al. (2008) Food Hydrocolloids 22: 587
Not performed yet with plant proteins?
Scaling up?
Fibril formation
Extensive heating and shearing at low pH renders protein fibrils
Unique property: very low critical gelling concentration
Drawbacks: yield (conversion) + upscaling
1000 nm
1000 nm
WPI fibrils Ovalbumin fibrils
Munialo (2013)TIFN
Extrusion
Thermal and mechanical energy input at low to medium
moisture conditions
Protein concentrates or flours are mixed with water, pushed
through a cylinder (turning screw). Moisture is evaporated
forming dry fibrous, porous granules or chunks
Texturized vegetable protein (TVP)
Microfibrillar protein network due to unfolding, orienting and thermal
crosslinking (temperature well above denaturation temp.)
Dry texturized proteins with high water binding & swelling capacity
Extrusion of soy protein
During extrusion denaturation and chemical
reactions decrease solubility
Moisture content affects solubility
28% moisture 60% moisture
buffer
denaturing agents to increase solubility (e.g. SDS, urea, mercapto-ethanol)
Chen et al. (2011) Food Sci Techn 44:957
Extrusion of other plant proteins
Literature shows that pea protein can be extruded and has similar
properties as extruded soy proteins
Nothing available yet on extruded lupine protein
Role of gluten and starch in extrusion of plant proteins under
investigation in Cluster project TNO
Valess
milk proteins + polysaccharides (alginate from sea weed)
extensive mixing � phase separation of biopolymers
formation of structure through addition of Ca2+
Patent by Kweldam US2011244090
Ojah Beeter
Sold by ao Vegetarische slager
Based on plant proteins (and probably polysaccharides from
seaweed)
glutenfree
Structure formation by sheeting/lamination of pressed heated protein
Questions?