The physical properties of fish gelatin gel are enhanced by the cross-linking activity of olive leaf water extract

A cold-water extract prepared from olive tree leaves (Olea europaea L.) was utilised to enhance the mechanical strength and melting temperature of fish gelatin (FG) gel. At concentrations of 5.0% (w/v), olive leaf extract (OLEx) enhanced the breaking stress and strain of FG gel by 11.6- and 1.9-fold, respectively. The melting temperature of FG gel was positively correlated with OLEx levels with FG gel not melting even at temperatures exceeding 80 degrees C, with the addition of 0.5% (w/v) OLEx. Chemical analysis of FG protein indicated that OLEx induced graft polymerisation of the FG polypeptide chains by reacting with the primary amino groups of FG. Oleacein, the major phenolic compound, purified from OLEx, acted as a cross-linker, enhancing the breaking strength of the gel, suggesting its predominant role in the gel-enhancing activity of OLEx. Thus, OLEx demonstrates significant potential as a natural modifier for enhancing FG gel properties. An olive leaf polyphenol oleacein polymerises fish gelatin polypeptide chains, resulting in the enhancement of the mechanical properties of fish gelatin gel.image