Proteins Functionality & Application. Anneke Martin

Proteins – Functionality & Application

Content

Functionality

Techno-functionality of proteins Interfacial properties

Gelation properties

Type of protein networks Water holding

Texturizing of proteins Available methods Extrusion

Three areas of functionality

Physiological functionality

Physiological functionality Nutritional functionalityNutritional functionality Physical functionality Physical functionality … protein structure & conformation protein structure & 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)

Different classes of ingredient functionality

Functionality Property Example

Techno-functional Solubility Solubility Precipitation

Bulk rheology

Thickening Gelling Texturizing Surface activity Foaming

Emulsifying

Sensory Binding of lipids/flavors

Bio-functional Nutritional

Digestibility Allergenicity Anti-microbial Physiological ACE inhibition

Techno-functional properties of proteins

Function Mechanism Food

solubility hydrophilicity beverages

viscosity water binding

hydrodynamic size

soups, gravies, dressings water binding hydrogen bonding meat/sausages, cakes, breads gelation network formation meats, sausages, pasta, baked

goods elasticity hydrophobic interactions

disulfide crosslinks

meat products, bakery products emulsification interfacial adsorption

film formation

sausages, soups, dressings, desserts

foaming interfacial adsorption film formation

whipped toppings, cakes, mousse, nougat

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)

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

Examples of foods with interfaces

solid liquid gas

solid solid 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 C O N T IN U O U S P H A S E

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

Gelation properties

gelatin

whey protein

soy protein

MOLECULAR DENATURATION/

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

• particle

determines 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

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

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

Water binding/holding

Relevant for juiciness, tenderness

Water holding capacity in meat Water holding capacity in meat proteins

[NaCl] ↑

plasma [gelatin]

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

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

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

Structuring of proteins

Formation of fibrillar-like structures of protein to mimic meat

Electrospinning Shear cell

Fibril formation at low pH Extrusion

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

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

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.)

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+

Ojah Beeter

Sold by ao Vegetarische slager

Based on plant proteins (and probably polysaccharides from seaweed)

glutenfree