Food Biochemistry and Food Processing (2 edition)

BLBS102-c20 BLBS102-Simpson March 21, 2012 13:35 Trim: 276mm X 219mm Printer Name: Yet to Come

20 Fish Collagen 371

Pepsin

Decomposed

matter removal

(A)

(C)

(B)

Pepsin Pepsin Pepsin Pepsin

Pepsin Pepsin Pepsin Pepsin

Pepsin Pepsin Pepsin

PSC

Atelocollagen

Other Collagen

proteins

Tissue

Figure 20.4.Collagen extraction with the aid of pepsin in 0.5 M acetic acid at 4◦C. (A) Collagenous tissue degradation. (B) The cleavage of

telopeptide region of collagen by pepsin. (C) Pepsin soluble collagen (PSC) or atelocollagen.

(based on hydroxyproline content), respectively, whereas colla-

gen extracted with 0.15 M HCl had the yield of only 18%. The

positively charged amine groups of protein can bind with anions

(Cl−), reducing electrostatic repulsive forces between charged

groups. As a consequence, the structure of collagenous fibers is

tightening, the ability of bonding water decreases, and the solu-

bility of collagen is, therefore, reduced (Skierka and Sadowska

2007).

Pepsin Solubilization Process

Generally, typical acid solubilization process renders a low yield

of collagen. To tackle the problem, pepsin has been applied

because it is able to cleave peptides specifically in telopeptide re-

gion of collagen, leading to increased extraction efficiency (Fig.

20.4; Nagai et al. 2002a, Nalinanon et al. 2007). Use of pepsin as

the aid for collagen extraction is a potential method for several

reasons: (1) some of noncollagenous proteins are hydrolyzed

and are easily removed by salt precipitation and dialysis,

improving collagen purity; (2) hydrolyze those components and

telopeptides of collagen to make the sample ready to solubilize in

acid solution, resulting in improvement of extraction efficiency;

(3) reduce antigenicity cause by telopeptide in the collagen

which serve as the major problem in food and pharmaceutical

applications (Werkmeister and Ramshaw 2000, Lee et al. 2001,

Lin and Liu 2006, Cao and Xu 2008). Pepsin, particularly pepsin

from porcine stomach, has been used to maximize the extraction

efficiency of collagen from several species such as largefin