Effect of kiam wood extract as influenced by ph during oxygenation on mackerel surimi gel

Impact of ethanolic kiam wood extract (EKWE) oxygenated at various pHs on the properties of gels from mackerel (Rastrelliger kanagurta) surimi was studied in comparison with commercial tannin (CT). When 0.3% CT and 0.15% EKWE oxygenated at alkaline pHs (8 and 9) were incorporated, surimi gel had the increases in breaking force by 123.4-135.7% and 136.9-157.5%, respectively, while the deformation was increased by 20.9-38.1% and 33.7-48.2%, respectively, compared with those of the control (P<0.05). Those increases were associated with the lowered expressible moisture content and the disappearance of myosin heavy chain band intensity. However, CT and EKWE oxygenated at pH 3 and 7 showed no pronounced effect. Gels added with 0.15% EKWE oxygenated at alkaline pH had the finer matrix with smaller strands and voids. Thus, the pH for oxygenation of phenolic compounds in EKWE had the impact on the gel strength of mackerel surimi. PRACTICAL APLICATIONS: Gel strength is a prime factor determining the quality and price of surimi. Several additives have been used to improve the gel strength. Recently the use of phenolic compounds in their oxidized form effectively enhanced gel strength of surimi. The extract from kiam wood is another natural additive exhibiting gel strengthening effect. Oxygenation of the extract at alkaline pH could increase the efficacy of the extract, in which the lower amount was required and no negative effect on the resulting gel was obtained.