Characterization of gelatins from Nile tilapia skins preserved by freezing and salting

Abstract

After Nile tilapia skin was preserved using the methods of freezing and dry salting, characteristics of skin gelatin were evaluated with regard to yield, rheological features and physical and chemical properties. Preservation was performed after filleting, at which time skins were either frozen (-18°C) for 7 days or salted (25°C) for 7 days. Although no differences (p > 0.05) were observed with respect to humidity, protein, lipid, ash and calcium levels, gelatin from salted skins had a higher concentration of iron relative to frozen skins. Further, twenty-three fatty acids were detected in salted skins compared with merely three found in skin derived gelatin. Of amino acids found, glycine, alanine, proline and arginine were the most abundant. Hydroxyproline abundance in salted and frozen skin gelatin were 8.76% and 8.71%, respectively. In addition, salted skin gelatins had a greater accumulation of saturated fatty acids and lower rates of monounsaturated fatty acids. Salted skin gelatin had the highest yield (18g × 100g-1), gel strength (200 g) and viscosity (19.02mPas) when compared to the yield (17g × 100g-1), gel strength (12.7g) and viscosity (9.16 mPas) of frozen skins. Results show that gelatin from dry salted skin had the best yield and also had relatively better rheological properties, more iron, and better coloration relative to gelatin obtained from frozen skins of Nile tilapia.

The effects of polyphenols on fresh quality and the mechanism of partial freezing of tilapia fillets

“…Freezing storage consumes much energy and ice crystals easily lead to changes in the quality of fish. 1 Chilled storage could not completely inhibit the biochemical reaction and bacteriological activity, affecting the flavor, color, texture and nutritional values of fish. 2 However, chemical preservation is efficient in trace amounts, bringing health risks to consumers.…”

“…Traditional preservation methods mainly include freezing storage, chilled storage and chemical preservation. Freezing storage consumes much energy and ice crystals easily lead to changes in the quality of fish 1 . Chilled storage could not completely inhibit the biochemical reaction and bacteriological activity, affecting the flavor, color, texture and nutritional values of fish 2 .…”