Protein Functionality FDSC400

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

Concentration Viscosity Dilute Semi-dilute Concentrated rgrg Hydrodynamic Functionality

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

Dough stretched Dough released Time Length +SO 3 2- Creep

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 2D Gel Loose, disordered, flexible chains Loop-train-tail model

electrostatic (a magnification of the lamella between two touching bubbles or two emulsion droplets) steric Emulsion Stabilization 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) GG reaction Substrate Product intermediate Enzyme stabilized intermediate

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

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