Extraction and characterisation of gelatine from Atlantic salmon (Salmo salar) skin

Gelatine was extracted from Atlantic salmon and Atlantic cod skin by the acid extraction process. After filtration and ion exchange treatment the extracts were colourless and free from fishy odour. In three separate experiments the average yields of gelatine from salmon and cod skins were 39.7% (+/-2.2%) and 44.8% (+/-0.2%) respectively, on a dry matter basis. Gelatine from salmon contained slightly more hydroxyproline and proline (16.6%) than cod gelatine (15.4%), whereas the content of serine was lower (4.6% versus 6.3%). Salmon gelatine expressed slightly higher gelling temperature (12 degrees C) than cod gelatine (10 degrees C), and higher initial gel strength. During storage at 10 degrees C, gel strengths were increased and more so with gels made from cod than from salmon gelatine. Hence, gels made from cod and salmon gelatines extracted at 56 degrees C achieved the same gel strength (195g) after 7days of storage. Gelatines extracted at a higher temperature (65 degrees C) gave lower gel strengths.