Gel-Forming Ability of Mackerel (Rastrelliger Branchysoma) Protein Isolate as Affected by Microbial Transglutaminase

The properties of gel from short-bodied mackerel (Rastrelliger branchysoma) alkaline-solubilized protein isolate with different levels (0, 0.25, 0.5, 1.0 and 1.5 unit/g sample) of microbial transglutaminase added (MTGase) and subjected to setting at 40 °C for 30 min, prior to heating at 90 °C for 20 min were investigated. The breaking force of the protein isolate gels with MTGase added at all levels was higher than that of the control gel (without the addition of MTGase) (p < 0.05). However, the increase in the amount of MTGase added had no effect on the breaking force of protein isolate gels (p > 0.05). From the result, no changes in deformation in all gels treated with and without MTGase were noticeable (p > 0.05). The lowest expressible moisture was found in the gel with 0.25 unit/g of MTGase (p < 0.05). Generally, the whiteness of all gels incorporating MTGase were lower than that without MTGase (p < 0.05). Therefore, the addition of MTGase at 0.25 unit/g sample in combination with an appropriate heating regime was a promising means to improve the gel properties, especially strength and water holding capacity, of short-bodied mackerel protein isolate prepared by alkaline solubilization.