Effect of oxidized kiam wood and cashew bark extracts on gel properties of gelatin from cuttlefish skins

The effects of ethanolic kiam wood extract (EKWE) and ethanolic cashew bark extract (ECBE) oxygenated at different pHs (8, 9 and 10) on gel properties of gelatin from cuttlefish skins were investigated. With the same extract, gel strength of gelatin increased as the pH for oxygenation of the extract increased (p<0.05). The increases in a⁎ and b⁎-values of gelatin gels were noticeable with the addition of either extracts oxygenated at increasing pHs (p<0.05). Cuttlefish skin gelatin gels with EKWE or ECBE oxygenated at pH 9 had the fewest free amino groups, suggesting the cross-linking of gelatin via amino groups. The greater number of non-disulfide covalent bonds was noticeable in the gels with extracts oxygenated at higher pH. An increase in gel strength was observed when the concentration of extracts (1–8%, w/w) increased (p<0.05). At the same concentration of extract, gelatins with EKWE had a higher gel strength than those with added ECBE (p<0.05). The a⁎-values of the gels increased as the concentration of oxygenated EKWE or ECBE increased (p<0.05). The larger strands and larger voids in the gel matrix were observed with gels with added oxygenated EKWE or ECBE, compared with the control gel. Therefore, either oxidized extracts could act as a potential gel enhancer of gelatin.