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Protein Functionality

Protein Functionality. FDSC400. Goals. Hydrodynamic-Aggregation Viscosity, Elasticity, Viscoelasticity Solubility, Water holding capacity Hydrophobic- Surface Active Emulsion and foam stabilization Flavor binding. Hydrodynamic Functionality. Dilute. Semi-dilute. r g. Viscosity.

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Protein Functionality

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  1. Protein Functionality FDSC400

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

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

  4. 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

  5. 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

  6. 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

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

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

  9. 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 Water Binding

  10. Solubility

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

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

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

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

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

  16. 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

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

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