Effect of MTGase, Dietary Fiber and UV Irradiation Upon Heat-Induced Gilthead Seabream (Sparus aurata) gels

The effects of microbial transglutaminase (MTGase, 0.5%, w/w), dietary fiber (konjac flour, Kjc, 1. 0%, w/w) and ultraviolet irradiation, UV (254 nm, 3300 mu W/cm(2) and 40 min), on heat-induced gels from gilthead seabream mince (Sparus aurata) were studied. MTGase addition improved texture, force at rupture increased from 44.3 +/- 18.1 to 131.9 +/- 56.7 N, and increased pH and water-holding capacity. Moreover, MTGase reduced the elastic modulus E(1) and darkened the gels; protein solubility declined, meaning greater protein aggregation, according to electropherograms. Evidence was found that disulfide bonding has a role in textural improvement by MTGase. Kjc increased the hardness from 15.1 +/- 3.1 to 20.6 +/- 4.7 N, the elastic modulus and WHC. Kjc itself and not its effect upon proteins may explain the hardening effect. However, gels containing Kjc were less deformable and Kjc reduced the extractable protein in the various selective bond media. UV did not present advantages as a gelation-promoting technology. MTGase and Kjc were texturally advantageous, although without synergies for gel strength: it fell from 56.9 +/- 7.1 to 24.6 +/- 5.9 N mm as a result of adding Kjc to gels containing MTGase. Nevertheless, the hardening effect of Kjc and MTGase combined surpassed the sum of the individual effects, thereby indicating the existence of a mutual reinforcement of the hardness through MTGase and konjac. Additionally, this study showed that gilthead seabream may be used to produce good quality (concerning texture, color and WHC) heat-induced gels.