Food Emulsifiers and Stabilizers - Food Shelf Life Stability: Chemical, Biochemical, and Microbiological Changes - page 242

TABLE 7.14
Amino Acid Side-Groups in Proteins
for Chemical Modifications

Group Modification

Amino (lys) Acylation; akylation

Carbonyl (asp, glu) Esterification; amide formation

Disulfide (cystine) Reduction

Sulfydryl (cys)
Thioether (met)

Alkylation; oxidation

Imidazole (his)
Indole (trp)
Phenolic (phe)

Acylation

Guanidino (arg) Condensation by dicarbonyls

TABLE 7.15
Parameters Relating to BLG Adsorption
at the Air-Water Interface: Average
Area Cleared Per Protein Molecule, dA,
and Apparent Number of Amino Acid
Residues Penetrating Interface (N

) a

τ

pH Time/min d A /nm 2 b N τ

4.06 0.8-8 2.9 19

4.06 60-360 20.6 137

5.05 0.4-10 5.1 34

5.05 6-360 13.1 87

5.85 6-360 11.9 79

6.36 2-60 7.7 51

a Adapted from Waniska and Kinsella. 174
b The quantity d A is calculated from the equation
ln(d∏/d t ) = ln( Kc )-∏ d A / kT ,
where K is the first-order rate constant of adsorption
(or rearrangement), c is the effective concentration of
active groups, k is Boltzmann's constant, and T is the
temperature.

Arai and Watanabe 175 have written an excellent review on the properties of
enzymatically modified proteins and compared chemical and enzymatic processes
on various proteins. Enzymatic processes are generally carried out under much
milder conditions providing safer experimental conditions. Proteolytic enzymes have
been shown to improve the solubility of proteins such as soy, leaf protein concen-
trates, fish protein concentrates, meat proteins, egg proteins, milk proteins, and blood