Chapter 11: Proteins: Amino Acids and Peptides Part 2

• Loosening or unfolding of the tertiary and sometimes secondary structure

• Sometimes reversible

• Involves only H-bonds

Breaking disulfide cross-links

Permanent denaturation, which results when liquid or semiliquid proteins form solid or semisoft clots

• Changes its physical characteristics

• Alters the ability to bind with water

• Interferes with biological interactions of enzymes

Beaten egg whites

Coagulated proteins, ex: cooked eggs

1) Temperature changes
2) Mechanical actions
3) Sound waves and irradiation

Heat: speeds up denaturation
Cold: may cause curdling

Disrupt: beating, rolling, kneading

| Strengthens gluten: kneading

Prolonged exposure at high levels is needed

1) Change in pH

| 2) Exposure to mineral salts or metals

Sour cream, buttermilk, yogurt

Sodium and potassium salts

• Water absorption

• Solubility

• Viscosity

• Stability in acids and alkalis

1) Proteins form gels
2) Proteins change texture
3) Proteins emulsify
4) Proteins form foams
5) Proteins develop gluten

Mixture of fluids locked in a tangled mesh of denatured and coagulated protein

1) 3D molecular structure

| 2) Liquid attracted to the protein

Acids soften gelatin, which may develop syneresis if stored or cooked for too long

Mineral salts, hard water, more gelatin, slow coolin rates

Acids, sugars, food pieces, rapid cooling

When salt is added to destabilize proteins

Spun into fibers under the right conditions

• Soy protein to create meat substitutes by denaturation or heat-coagulation under pressure

• To produce processed cheeses

Denatured protein

Polar side chain attracts water-based liquid and nonpolar side attracts oil

Pressure used in homogenization of milk ENABLES casein to act as an emulsifier

Protein's ability to form an emulsion

Gas suspended in liquid or semi-solid

By bubbling gas through a mixture, beating or whipping, and depressurization

Meringue, foam cakes, marshmallows, soufflés, bread

Albumin in egg whites and milk

Strongly cohesive and elastic protein

When a high protein flour is combined with moisture and stirred or kneaded

Disulfide cross-links formed during kneading

Gluten coagulates when baked

High temperature and prolonged cooking

Protein molecules shrink and squeeze out H2O, resulting in a dry, rubbery, tough product

1) Support growth and repair
2) Fight disease
3) Maintain fluid and mineral balance
4) Maintain pH balance
5) Control bodily functions
6) Provide energy

Pick up and release acids and bases (side chain)

Proteins are apart of hormones that maintain body functions and enzymes (chem reactions)

AA -> Energy (produces ketones and ammonia - strains kidneys)

1) Developed grains (triticale)

| 2) Using biotechnology

Allergies