Protein

1
Protein

• FCS 3120
• M. Burns

2
Protein Chemical components

• CHO N and sometimes S and P
• Structural features of amino acids
• R-group
• Levels of structure
• Primary, secondary and tertiary

3
Protein Classification

• Native proteins
• Simple proteins
• Globular
• Fibrous
• Conjugated
• Mucoproteins, lipoproteins, phosphoproteins,
  metalloproteins, nucleoproteins
• Derived proteins

4
Protein Properties

• Amphoteric
• Function as an acid or base
• Isoelectric point
• Increases stability in dispersion
• Hydration
• Ability to bind water
• Helps protein stay dispersed

5
Protein Reactions

• Hydrolysis
• Cleavage of backbone chain of protein molecule
  into shorter chains with uptake of water molecule
• Caused by hydrolytic enzymes

6
Protein Reactions

• Maillard reaction
• Chemical reaction of amino group of protein with
  aldehyde group of sugar
• One type of non-enzymatic browning
• Issue of concern in food industry

7
Protein Reactions

• Denaturation
• Most important property of food protein
• Physical process whereby protein molecule is
  changed in shape, but backbone (AA chain) remains
  intact
• Unfolding of tertiary structure

8
Protein reactions

• Coagulation
• Clotting of protein
• Gel (based custard)
• Sol (stirred custard)
• Precipitate out (curdled milk)

9
Causes of coagulation

• Heat (not casein)
• Freezing
• Agitation
• Acid
• Salts
• Phenolic compounds

10
Functional Properties of Protein

• Ability to form stable foams (gelatin/eggs)
• Thickening (eggs)
• Cell structure and rigidity (gluten)