Proteins

1. Amino acids!
   1. 20 aa in a protein
      1. 9 essential, 11 non-essential
         1. Need essential from diet for body to make non-essentials
         2. Withut essential aa, no protein formed.
   2. P broken down into aa by Hydrolysis - eg saliva

      Annotations:

      • Breaking of bonds by adding water
   3. Not stored in body long - fresh supply of essental aa required daily.

Annotations:

• Because they contain all the essentail amino acids in the amounts needed to support protein tissue formation by the body.

1. SOLUBILITY

   Annotations:

   • differences determined by amino acid sequence and composition
   1. Soluble in water: histones (protein replication), ovalbumims (egg whites), lactalbumin (milk), albumins of blood.
   2. Insoluble in water: keratin (hair/fingernails), collagen (bones, cartilage, connective tissue, epidermis)
   3. Soluble in weak salt solutions: myosin (muscle tissue), lactoglobins (milk)
   4. Soluble in acids: wheat glutenin, oryzenin (rice)
2. Water bindning
   1. Through hydrogen bonding w/- muscle tissue of meats (ground products ie hot dogs, mince)
3. Structure
   1. Primary: molecular weight, aa composition & seq along peptide chain.
   2. Secondary: shape of coiled helix
   3. Tertiary: folding of a chain over itself
   4. quartenary: 2 or more polypeptide chains join
   5. Changed through food processing
4. Denaturation: change in strcuture without breaking covalent bonds, or aa seq.
   1. Loss of biological activity & changes in physical/functional proeprties (ie solubility)
   2. Caused by heat, acids, solvents, concetrated salts, surface forces.
   3. eg. 'Blanching; in freezing/canning fruits & veg, Cheeses/Yogurts, Hardening of egg whit in pan (heat denaturation), whipping of egg whites to foam (surface force), slow cooking meat.
   4. Contributes to flavour & texture of food.
5. Reduction:
6. Hydrolysis: cleaving of peptide bonds by adding water molecule.
   1. Complete: P broken down to aa cparts
      1. Partial: protein hydrolsates,: flavours parts of soups, sauces, gravy. plant prteins hydrolysed by hydrochloric acid - neuatralised with alkali.