Protein Functionality FDSC 400 Goals HydrodynamicAggregation Viscosity Elasticity

Protein Functionality FDSC 400

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

rg Concentrated Viscosity Dilute Semi-dilute Hydrodynamic Functionality Concentration

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

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

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

Creep Length Dough stretched released Time +SO 32 -

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

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

Solubility

Hydrophobic/Surface Functionality • Emulsion stabilization • Foam destabilization • Flavor binding

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

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

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

Polyphenol oxidase • Founds in plans, animals and some microorganisms, requires Cu 2+, O 2 diphenol catechol MELANINS phenol

Lipoxygenase • Catalyzes peroxidation of fatty acids. • Abstracts an H , allows reaction with O 2, free radicals produced • Leads to rancidity and flavor • Co-oxidations – Bleaching flour – Thiols – Vitamins

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