1. Protein Functionality

2. FUNCTIONAL PROPERTIES OF FOOD PROTEINS
Hydration
Solubility
Viscosity
Gel formation
Texture
Dough formation
Emulsification
Foaming
Aroma binding
Interaction with other food components
The proteins have a major effect on the structure and sensory quality of numerous foods in fresh and processed conditions, for example on the consistency and texture of meat and meat products, milk and cheese, pasta and bread.
Food quality most often depends on the structural and physico-chemical quality of the protein components.
Some of these functional properties are: hydration, solubility, viscosity, gel formation, texture, dough formation, emulsification, foaming, aroma binding and interaction with other food components.

3. Goals Hydrodynamic-Aggregation Hydrophobic- Surface Active
Viscosity, Elasticity, Viscoelasticity
Solubility, Water holding capacity
Hydrophobic- Surface Active
Emulsion and foam stabilization
Flavor binding

4. Hydrodynamic Functionality
Dilute
Semi-dilute rg
Viscosity
Concentrated
Concentration

5. Viscosity A property of LIQUIDS
Viscosity is the resistance to flow. The amount of energy you need to expend to get a given flow rate.
Stress (force per unit area) is proportional to rate of strain (i.e., flow rate)
Particles of any type in a fluid will increase its viscosity
Large, well hydrated polymers contribute most to viscosity

6. Elasticity A property of SOLIDS
Elasticity is the force to achieve a given percentage change in length
Stress (force per unit area) is proportional to strain (fractional deformation)
An elastic material must have some solid-like network throughout the structure
The more load bearing structures the more elastic
The more inter-structure links the more elastic

7. Viscoelasticity
Many materials simultaneously show solid and liquid like properties
If they are stretched they will partly and slowly return to their original shape
Elastic solids would completely recover
Viscous liquids would retain their shape

8. Creep
Dough stretched
Dough released
+SO32-
Length
Time

9. Mechanisms of Link formation
Hydrophobic (following denaturation or hydrolysis)
Thiol-disulfide interchange
Enzymic crosslinking
Also consider repulsive effects (charge)

10. Water Binding Gel contains pores Water can flow out of the pores
If the gel contracts it may expel liquid SYNERESIS
Due to closer association of protein with protein
Casein gels are very porous structures and water can easily flow out of them, either if an external pressure is applied or if the casein strands are allowed to fold into a tighter conformation and so squeeze the water out. Breaking casein strands or increasing the attractive forces can lead to syneresis.
The amount of syneresis in cheese curd is a major determinant of the moisture content of the finished cheese. Cutting the curd allows some realignment of the gel structure and some moisture is squeezed out.

11. Solubility

12. Hydrophobic/Surface Functionality
Emulsion stabilization
Foam destabilization
Flavor binding

13. Whey vs. Casein Dense, ordered globular proteins 2D Gel
Loose, disordered, flexible chains
Loop-train-tail model

14. Emulsion Stabilization
Proteins adsorbed to surfaces can stabilize emulsions and foams by various mechanisms
Proteins are often denatured on binding
electrostatic
steric - - - - - - - - - - - - - -
(a magnification of the lamella between two touching bubbles or two emulsion droplets)

15. Food Enzymes Biological catalysts Proteins (can be denatured)
Specific (can be inhibited)
intermediate
Enzyme stabilized intermediate DG
Substrate
Product
reaction

16. Polyphenol oxidase
Founds in plans, animals and some microorganisms, requires Cu2+, O2
diphenol
phenol
MELANINS
diphenol
catechol

17. Lipoxygenase Catalyzes peroxidation of fatty acids
Abstracts an H., allows reaction with O2, free radicals produced
Leads to rancidity and flavor
Co-oxidations
Bleaching flour
Thiols
Vitamins

18. Amylase Starch Dextrins Glucose Fructose a-amylase (endo-splitting)
glucoamylase
Starch Dextrins Glucose
Highly viscous suspension of polymerized corn starch
Glucose isomerase
Fructose
105°C