345
warm-water fi sh gelatins. This is due to the cold-water fi sh having lower concentrations of proline and hydroxyproline than the other species;
– cold-water fi sh gelatin solutions behave as viscous liquids at room temperature,
which could make them desirable for specifi c applications, such as ice cream,
yogurt, dessert gels, confections, and imitation margarine;
– fi sh gelatin had less undesirable fl avors and odors, as well as better release of
aroma, than the same product made with pork gelatine with an equal Bloom
value and higher melting point,” (Avena-Bustillos et al. 2011 ; see also AvenaBustillos et al. 2006 ; Choi and Regenstein 2000 ; Regenstein and Chaudry 2002 ;
Solgaard et al. 2008 ).
Fish Skin Gelatin Due to low concentration of intra and inter-chain non-reducible
crosslinks the collagen of the fi sh skins origin is highly soluble (Gimenez et al.
2005 ). Moreover, both technical (Gomez-Guillen et al. 2002 ; Fernandez-Dıaz et al.
2003 ; Songchotikunpan et al. 2008 ) and edible (Aberoumand 2010 ) gelatin can be
produced from fi sh skins. Gimenez and co-workers, after analysis of papers by
Gustavson 1956 ; Norland 1990 and Johnston-Banks 1990 , described solubilisation
of fi sh skin collagen as follow:
“Therefore, a mild acid pre-treatment is usually used for gelatin production.
Such treatment leads to a type-A gelatin with an isoelectric point that can vary from
6.5 to 9. Increasing H
+ ions favours the access of water to collagen fi bres. This water
is held in by electrostatic forces between charged polar groups (electrostatic
swelling) or by hydrogen bonding between uncharged polar groups and negative
atoms (lyotropic hydration). The type and concentration of acid used strongly infl uences swelling properties and solubilisation of collagen. This leads to variations in
molecular weight distribution in the resultant gelatins, depending on the persistence
of some of the cross-links between collagen chains,” (Giménez et al. 2005 ).
According to Asghar and Henrickson ( 1982 ), “the lyotropic effect of carboxylic
acids on collagen seems to dominate the swelling capacity, rather than a specifi c
ion effect. It is the non-ionized acid that acts as the swelling agent. This occurs by
competition with the peptide group involved in intermolecular linking of the
protein chain; and is due mainly to the hydrogen bonding power of the acid. Citric
acid is widely used for the manufacture of foodgrade gelatin from fi sh skin because
it does not introduce undesirable colour or odour to the gelatin. The overall properties of gelatins obtained following this procedure highly depend on the fi sh species
used, and are largely attributed to differences in amino acid composition,” (Giménez
et al. 2005 )
On example of megrim ( Lepidorhombus whiffi agonis ) skin, it was shown that
also lactic acid can be used for collagen extraction (Gomez-Guillen et al. 2002 ;
Gimenez et al. 2005 ). Different optimal conditions have been used to extract gelatin
from fi sh skin: 0.115 M (84 min) acetic acid (Wang and Yang 2009 ), 0.115 M acetic
acid plus 0.2 M (3 h) NaOH (Wang and Yang 2009 ), acetic acid plus ~0.1 M NaCl
(Montero and Gomez-Guillen 2000 ), and acetic acid, NaOH and NaCl (Montero
and Gomez-Guillen 2000 ). Comparative studies at nano scale into the effect of different pretreatment sets have only been done for acetic and acetic-NaOH (Wang and
9 Marine Gelatins
warm-water fi sh gelatins. This is due to the cold-water fi sh having lower concentrations of proline and hydroxyproline than the other species;
– cold-water fi sh gelatin solutions behave as viscous liquids at room temperature,
which could make them desirable for specifi c applications, such as ice cream,
yogurt, dessert gels, confections, and imitation margarine;
– fi sh gelatin had less undesirable fl avors and odors, as well as better release of
aroma, than the same product made with pork gelatine with an equal Bloom
value and higher melting point,” (Avena-Bustillos et al. 2011 ; see also AvenaBustillos et al. 2006 ; Choi and Regenstein 2000 ; Regenstein and Chaudry 2002 ;
Solgaard et al. 2008 ).
Fish Skin Gelatin Due to low concentration of intra and inter-chain non-reducible
crosslinks the collagen of the fi sh skins origin is highly soluble (Gimenez et al.
2005 ). Moreover, both technical (Gomez-Guillen et al. 2002 ; Fernandez-Dıaz et al.
2003 ; Songchotikunpan et al. 2008 ) and edible (Aberoumand 2010 ) gelatin can be
produced from fi sh skins. Gimenez and co-workers, after analysis of papers by
Gustavson 1956 ; Norland 1990 and Johnston-Banks 1990 , described solubilisation
of fi sh skin collagen as follow:
“Therefore, a mild acid pre-treatment is usually used for gelatin production.
Such treatment leads to a type-A gelatin with an isoelectric point that can vary from
6.5 to 9. Increasing H
+ ions favours the access of water to collagen fi bres. This water
is held in by electrostatic forces between charged polar groups (electrostatic
swelling) or by hydrogen bonding between uncharged polar groups and negative
atoms (lyotropic hydration). The type and concentration of acid used strongly infl uences swelling properties and solubilisation of collagen. This leads to variations in
molecular weight distribution in the resultant gelatins, depending on the persistence
of some of the cross-links between collagen chains,” (Giménez et al. 2005 ).
According to Asghar and Henrickson ( 1982 ), “the lyotropic effect of carboxylic
acids on collagen seems to dominate the swelling capacity, rather than a specifi c
ion effect. It is the non-ionized acid that acts as the swelling agent. This occurs by
competition with the peptide group involved in intermolecular linking of the
protein chain; and is due mainly to the hydrogen bonding power of the acid. Citric
acid is widely used for the manufacture of foodgrade gelatin from fi sh skin because
it does not introduce undesirable colour or odour to the gelatin. The overall properties of gelatins obtained following this procedure highly depend on the fi sh species
used, and are largely attributed to differences in amino acid composition,” (Giménez
et al. 2005 )
On example of megrim ( Lepidorhombus whiffi agonis ) skin, it was shown that
also lactic acid can be used for collagen extraction (Gomez-Guillen et al. 2002 ;
Gimenez et al. 2005 ). Different optimal conditions have been used to extract gelatin
from fi sh skin: 0.115 M (84 min) acetic acid (Wang and Yang 2009 ), 0.115 M acetic
acid plus 0.2 M (3 h) NaOH (Wang and Yang 2009 ), acetic acid plus ~0.1 M NaCl
(Montero and Gomez-Guillen 2000 ), and acetic acid, NaOH and NaCl (Montero
and Gomez-Guillen 2000 ). Comparative studies at nano scale into the effect of different pretreatment sets have only been done for acetic and acetic-NaOH (Wang and
9 Marine Gelatins