347
(c) washing with water until the washing water is substantially neutral;
(d) treating with dilute aqueous mineral acid;
(e) washing with water until the washing water is substantially neutral;
(f) treating with dilute aqueous citric acid and/or another suitable organic acid;
(g) washing with water until the washing water is substantially neutral;
(h) extracting with water at elevated temperatures not above about 55 °C the washed
citric acid-treated skins. In practice, the present process employs much lower
temperatures than known heretofore for the treatment steps, which results in a
high quality product (e.g. absence of a fi shy smell).
Fish Scale and Bone Gelatin Scales (Wangtueai and Noomhorm 2009 ) and bones
(Alfaro et al. 2005 ) from many fi sh species proven to be a source for gelatin production (Cheow et al. 2007 ). Gelatin extraction procedure from fi sh scales is described
in lizardfi sh ( Saurida spp.) (Wangtueai and Noomhorm 2009 ) as follows:
“The thawed (kept in refrigerator at 9–10 °C for about 24 h) scales were treated
with 2 volumes (v/w) of alkali solution (0.1–0.9 % NaOH) at room temperature
(30 °C) for 1–5 h to remove the noncollagen protein and subcutaneous tissue after
they were swollen. After the alkali treatment, the scales were neutralized by washing under running tap water until they had a pH of about 7. The scales were then
subjected to a fi nal wash with distilled water to remove any residual matter. The
extractions were carried out in distilled water at control temperatures within the
range of 70–90 °C for 1–5 h. The ratio used was 300 g (weight of wet scales) to
600 ml of distilled water. The coarse solids were fi ltered out with fi lter cloth, and
this was followed by vacuum-fi ltering. The fi ltered solutions were evaporated under
vacuum to 10 brix at 50 °C and dried in a vacuum dryer at 60 °C set pressure 0 mbar
until brittle sheets were formed,” (Wangtueai and Noomhorm 2009 ).
Some biochemical properties of scale and bone gelatin of marine fi sh species
have been also investigated Ogawa et al ( 2004 ).
Fish Gelatin-Based Composites As reviewed by Bae et al ( 2009 ), researchers
have investigated various approaches to modify fi sh gelatin in an effort to improve
its functionality. The blending of fi sh gelatin with other biopolymers, such as
j- carrageenan, chitosan, and pectin, is one possible way to improve the properties of
fi sh gelatin. Furthermore, the addition of plasticizers, such as glycerol sorbitol,
sucrose, polyethylene glycol, and salt agents (Sarabia et al. 2000 ; Koli et al. 2011 )
can improve the mechanical properties of fi sh gelatin fi lms or gels. Additions of
chemical cross-linking agents, such as glutaraldehyde, formaldehyde, and glyoxal
or enzymes, such as microbial transglutaminase, have also been shown to improve
the properties of fi sh gelatin. However, the chemical cross-linkers are toxic, which
limits their use in food systems. Therefore, the use of enzymes as cross-linking
agents could be a better alternative for food packaging (Bae et al. 2009 ).
Experience in manipulating the physical properties of fi sh gelatins has been
gained during investigations of rheological (Gudmundsson 2002 ), mechanical
(Chiou et al. 2006 ), cross-linking (Bode et al. 2011 ) and gelling. The properties of
fi sh gelatins, as well as their interactions with other proteins (Badii and Howell
9 Marine Gelatins
(c) washing with water until the washing water is substantially neutral;
(d) treating with dilute aqueous mineral acid;
(e) washing with water until the washing water is substantially neutral;
(f) treating with dilute aqueous citric acid and/or another suitable organic acid;
(g) washing with water until the washing water is substantially neutral;
(h) extracting with water at elevated temperatures not above about 55 °C the washed
citric acid-treated skins. In practice, the present process employs much lower
temperatures than known heretofore for the treatment steps, which results in a
high quality product (e.g. absence of a fi shy smell).
Fish Scale and Bone Gelatin Scales (Wangtueai and Noomhorm 2009 ) and bones
(Alfaro et al. 2005 ) from many fi sh species proven to be a source for gelatin production (Cheow et al. 2007 ). Gelatin extraction procedure from fi sh scales is described
in lizardfi sh ( Saurida spp.) (Wangtueai and Noomhorm 2009 ) as follows:
“The thawed (kept in refrigerator at 9–10 °C for about 24 h) scales were treated
with 2 volumes (v/w) of alkali solution (0.1–0.9 % NaOH) at room temperature
(30 °C) for 1–5 h to remove the noncollagen protein and subcutaneous tissue after
they were swollen. After the alkali treatment, the scales were neutralized by washing under running tap water until they had a pH of about 7. The scales were then
subjected to a fi nal wash with distilled water to remove any residual matter. The
extractions were carried out in distilled water at control temperatures within the
range of 70–90 °C for 1–5 h. The ratio used was 300 g (weight of wet scales) to
600 ml of distilled water. The coarse solids were fi ltered out with fi lter cloth, and
this was followed by vacuum-fi ltering. The fi ltered solutions were evaporated under
vacuum to 10 brix at 50 °C and dried in a vacuum dryer at 60 °C set pressure 0 mbar
until brittle sheets were formed,” (Wangtueai and Noomhorm 2009 ).
Some biochemical properties of scale and bone gelatin of marine fi sh species
have been also investigated Ogawa et al ( 2004 ).
Fish Gelatin-Based Composites As reviewed by Bae et al ( 2009 ), researchers
have investigated various approaches to modify fi sh gelatin in an effort to improve
its functionality. The blending of fi sh gelatin with other biopolymers, such as
j- carrageenan, chitosan, and pectin, is one possible way to improve the properties of
fi sh gelatin. Furthermore, the addition of plasticizers, such as glycerol sorbitol,
sucrose, polyethylene glycol, and salt agents (Sarabia et al. 2000 ; Koli et al. 2011 )
can improve the mechanical properties of fi sh gelatin fi lms or gels. Additions of
chemical cross-linking agents, such as glutaraldehyde, formaldehyde, and glyoxal
or enzymes, such as microbial transglutaminase, have also been shown to improve
the properties of fi sh gelatin. However, the chemical cross-linkers are toxic, which
limits their use in food systems. Therefore, the use of enzymes as cross-linking
agents could be a better alternative for food packaging (Bae et al. 2009 ).
Experience in manipulating the physical properties of fi sh gelatins has been
gained during investigations of rheological (Gudmundsson 2002 ), mechanical
(Chiou et al. 2006 ), cross-linking (Bode et al. 2011 ) and gelling. The properties of
fi sh gelatins, as well as their interactions with other proteins (Badii and Howell
9 Marine Gelatins