Effect of oxidised tannic acid on the gel properties of mackerel (Rastrelliger kanagurta) mince and surimi prepared by different washing processes

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.