Comparison between gelatines extracted from mackerel and blue whiting bones after different pre-treatments.

Gelatines were extracted from mackerel and blue whiting bones after chemical or enzymatic pre-treatments and their functional properties (solubility, foaming and emulsifying properties) were analysed. The pre-treatment significantly (p<0.05) affected the composition and the functional properties of the extracted gelatines. The amino acid analyses showed that chemically pre-treated bone gelatines had higher imino acids (proline and hydroxyproline) contents compared to those extracted after the enzymatic pre-treatment, for both fish species. It was observed that all gelatines had higher solubility at low pH with a maximum value observed at pH 2. A significant effect of ionic strength was observed. Increasing the NaCl concentration to more than 1% resulted in a significant decrease of the solubility. Mackerel bone gelatines showed lower foaming capacity (FC) and higher foaming stability (FS) than blue whiting bone gelatines. Increasing the concentration of gelatine decreased the emulsifying activity index (EAI) but increased the stability index (ESI). The use of enzymes in the pre-treatment process gave gelatines with significantly (p<0.05) higher EAI and ESI.