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380 Part 3: Meat, Poultry and SeafoodsTable 20.5.The Maximum Transition Temperature (Tm) or Denaturation Temperature (Td) of Collagens from the
Skin of Several Fish SpeciesImino Acida
Content (%) TmorTd(◦C)Sources of Skin Collagen ASC PSC ASC PSC ReferencesCalfb 21.5 – 36.3 – Ogawa et al. (2003)
Young Nile perchb 19.3 – 36.0 – Muyonga et al. (2004)
Adult Nile perchb 20.0 – 36.0 – Muyonga et al. (2004)
Black drumb 20.0 19.7 34.2 35.8 Ogawa et al. (2003)
Sheepshead sea breamb 20.5 19.8 34.0 34.3 Ogawa et al. (2003)
Brownstripe red snapperc 21.1 22.1 31.5 31.0 Jongjareonrak et al. (2005)
Bigeye snapperc 19.3 – 32.5 31.5 Nalinanon et al. (2007)
Carpb 19.0 – 28.0 – Duan et al. (2009)
Channel catfishb 17.1 – 32.5 – Liu et al. (2007)
Pacific whitingb 16.4 – 21.7 – Kim and Park (2004)
Deep-sea redfishb 16.5 16.0 16.1 15.7 Wang et al. (2007)
Codb 15.4 – 15.0 – Duan et al. (2009)
Arabesque greenlingc 15.9 15.7 15.7 15.4 Nalinanon et al. (2010)
Brownbanded bamboo sharkc 20.4 20.7 34.5 34.5 Kittiphattanabawon et al. (2010a)
Blacktip sharkc 19.7 20.3 34.2 34.4 Kittiphattanabawon et al. (2010c)aImino acids include proline and hydroxyproline.
bThermal stability was expressed asTd.
cThermal stability was expressed asTm.collagens indicated some differences in the molecular structure.
However, the triple-helical structure of PSC from other species,
such as brownbanded bamboo shark (Kittiphattanabawon et al.
2010a) and blacktip shark (Kittiphattanabawon et al. 2010c),
was not affected by pepsin digestion during collagen extraction.
This confirms that pepsin specifically cleaves only at telopeptide
regions of tropocollagen.Thermal StabilityThe contents of imino acids (proline and hydroxyproline) are
related to thermal stability of collagen. Generally, collagens
containing small concentrations of both imino acids denature
at lower temperature than do those with the larger concentra-
tions. The maximal transition temperatures (Tm) or denaturation
temperatures (Td) of collagen from different fish are shown in Ta-
ble 20.5. A high content of imino acid is needed for stabilization
of collagen (Xu et al. 2002). The thermal stability of the collagen
triple helix is attributed to the hydrogen-bonded networks, me-
diated by water molecules, which connect the hydroxyl group of
hydroxyproline in one strand to the main chain amide carboxyl of
another chain (Babu and Ganesh 2001). Therefore, differences in
hydroxyproline content might determine the denaturation tem-
peratures of collagens from different species. Collagens derived
from fish species living in cold environments have lower con-
tents of hydroxyproline and they exhibit lower thermal stability
than those from fish living in warm environment (Muyonga et al.
2004). Therefore, the imino acid content of fish collagens is as-
sociated with their thermal stability and correlates with the water
temperature of their normal habitat (Foegeding et al. 1996). Nor-
land (1990) reported that collagen from cold-water fish consistedof imino acid about 16–18%. Muyonga et al. (2004) found that
ASC extracted from the skins of young and adult Nile perch
contain higher content of imino acids (19.3% and 20.0%, re-
spectively) than that from other fish species. The denaturation
temperature for the collagens from the skins of young and adult
Nile perch was determined to be 36◦C, which was higher than
that for most other fish species. The circular dichroism measure-
ment of type I collagens from fish scales ofPagrus majorand
Oreochromis niloticasindicated that the denaturation tempera-
tures were dependent on the amount of hydroxyproline rather
than proline residues. Raman spectra also indicated that the rel-
ative intensities of Raman lines at 879 and 855 cm−^1 assigned
to Hyp and Pro rings were changed due to the contents of the
imino acids (Ikoma et al. 2003). Nalinanon et al. (2010) reported
thatTmof collagens from the skin of arabesque greenling was
15.4–15.7◦C, which was in accordance with that of cold-water
fish species such as cod (15◦C) (Duan et al. 2009) and deep-sea
redfish (16.1◦C) (Wang et al. 2007). Denaturation temperatures
of skin collagen from several cold- and temperate-water fish
including carp (28◦C) (Duan et al. 2009), grass carp (28.4◦C)
(Zhang et al. 2007), ocellate puffer fish (28◦C) (Nagai et al.
2002a), tiger puffer fish (28.4◦C) (Bae et al. 2008), Japanese
seabass (26.5◦C), chub mackerel (25.6◦C), and bullhead shark
(25◦C) (Nagai and Suzuki 2000) have been reported. These col-
lagens had much lower denaturation temperature than those of
subtropical and tropical fish such as black drum (34.2◦C) (Ogawa
et al. 2003), sheephead sea bream (34◦C) (Ogawa et al. 2003),
bigeye snapper (32.5◦C) (Nalinanon et al. 2007), brownstripe
red snapper (30.5◦C) (Jongjareonrak et al. 2005), brownbanded
bamboo shark (34.5◦C) (Kittiphattanabawon et al. 2010a), and
blacktip shark (34.5◦C) (Kittiphattanabawon et al. 2010c). The