Effect of different pretreatments on functional properties of African catfish (Clarias gariepinus) skin gelatin

Abstract

Pretreatments with different types of alkali and acid were compared to determine their effects on gelatin extraction from African catfish (Clarias gariepinus) skin. The study was divided into three parts. In the first part, the skins were only treated with alkaline (Ca(OH)2 or NaOH) solution or pretreated with acetic acid solution. For second part, combination of alkali and acid pretreatment was carried out. For the third part, the skins were first treated with NaOH solution, followed by the treatment with acetic acid, citric acid or sulfuric acid solution. Functional properties including the yield of protein recovery, gel strength, viscosity, pH and viscoelastic properties were determined on gelatins obtained with different pretreatment conditions. Pretreatment with alkali removed noncollagenous proteins effectively, whilst acid pretreatment induced some loss of collagenous proteins. Combination of alkali and acid pretreatment not only removed the noncollagenous proteins and caused a significant amount of swelling, but also provided the proper pH condition for extraction, during which some cross-linkages could be further destroyed but with less breakage of intramolecular peptide chains. Pretreatment of catfish skins with 0.2 N NaOH followed by 0.05 M acetic acid improved yield of protein recovery, gel strength, viscosity, melting temperature and gelling temperature of gelatin extract.

Gelatin prepared from European eel (Anguilla anguilla) skin: Physicochemical, textural, viscoelastic and surface properties

“…The melting temperature of the European eel skin gelatin was found to be 21 °C. The melting point of EESG was lower than that reported for the gelatin from amur sturgeon skin (22 °C) and seabass skin (26.3 -27 °C) [7,38] and higher than that reported by [39] for African catfish skin gelatin (20.8 °C). The gelatin from fish sources possesses a lower gelling and melting temperature compared to a mammalian source due to a lower imino acid content.…”

Effect of acid treatment on extraction yield and gel strength of gelatin from whiptail stingray (Dasyatis brevis) skin

“…The gelatin extraction yields were remarkably improved by lowering the pH values. It is known that the swelling, hydration, and extraction of type A gelatins are favored at low pH (See et al, 2015), as also observed in the present study.…”

“…Further acid addition affected the extraction of collagen (in both pretreatments), probably due to undesirable acid hydrolysis, leading to the formation of low molecular weight peptides that could be lost by lixiviation during the ray skin washing steps (Jamilah and Harvinder, 2002;Zeng et al, 2010). Comparable results were reported by Jellouli See et al (2015), in which weak organic acids (acetic and citric) extracted more gelatin from African catfish (Clarias gariepinus) skin than a strong acid (sulfuric). The variation in gelatin yields among species is due to the differences in their skin conformation, besides the extraction conditions utilized.…”

Isolation and mass spectrometry based hydroxyproline mapping of type II collagen derived from Capra hircus ear cartilage

“…Furthermore, western blot analysis using anti-elastin antibody (Abcam, USA) confirmed absence of any elastin protein in the isolated COLII from Capra ear cartilage. The result indicates that NaOH pre-treatment for Capra ear cartilage is necessary for the removal of non-collagenous protein from tissue 30 .…”