Effect of oxidised tannic acid (OTA) at different levels (0, 0.25, 0.50 and 0.75% of protein content) on the
gel properties of mackerel (Rastrelliger kanagurta) mince and surimi prepared by different washing
processes was investigated. Breaking force and deformation of gels varied with washing processes and
concentrations of OTA. The gel of alkaline-saline washing process surimi (ASWPS) added with 0.25% OTA
had the increases in breaking force and deformation by 166.2 and 45.9%, respectively, compared with
that of conventional washing process surimi (CWPS) without OTA addition. Those increases were
associated with the lowered expressible moisture content. Electrophoretic studies revealed that the
greater polymerisation was found in ASWPS added with 0.25% OTA. Slight retention of myosin heavy
chain (MHC) with lowered trichloroacetic acid (TCA) soluble peptide contents was observed in ASWPS
gel added with 0.25% OTA, suggesting the decreased degradation induced by indigenous proteases. The
microstructure of ASWPS gels became more ordered, compact and denser with the addition of 0.25%
OTA. The use of OTA in conjunction with alkaline-saline washing process could improve the properties of
gel from mackerel surimi without adverse effect on sensory properties