Zhang Yan, Chang Sam K C
Coastal Research and Extension Center, Mississippi State University, Pascagoula, MS 39567, USA.
Department of Food Science, Nutrition and Health Promotion, Mississippi State University, Starkville, MS 39762, USA.
Foods. 2023 May 17;12(10):2029. doi: 10.3390/foods12102029.
The texture of surimi-like gels made from the protein isolate extracted from catfish byproducts has been proven to be brittle and lack elasticity. To address this issue, varying levels of microbial transglutaminase (MTGase) from 0.1 to 0.6 units/g were applied. MTGase had little effect on the color profile of gels. When MTGase at 0.5 units/g was employed, hardness, cohesiveness, springiness, chewiness, resilience, fracturablity, and deformation were increased by 218, 55, 12, 451, 115, 446, and 71%, respectively. A further increase in added MTGase did not lead to any textural improvement. In comparison to the gels made from fillet mince, the gels made from protein isolate were still lower in cohesiveness. Due to the activated endogenous transglutaminase, a setting step enhanced the textural properties of gels made from fillet mince. However, because of the endogenous proteases-induced protein degradation, the setting step led to a texture deterioration of the gels made from protein isolate. Gels made from protein isolate showed 23-55% higher solubility in reducing solution than in non-reducing solution, suggesting the vital role of disulfide bonds in the gelation process. Due to the different protein composition and conformation, fillet mince and protein isolate exhibited distinct rheological properties. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) showed the highly denatured protein isolate was susceptible to proteolysis and prone to disulfide formation during the gelation process. It also revealed that MTGase had an inhibitory effect on the proteolysis induced by endogenous enzymes. In view of the susceptibility of the protein isolate to proteolysis during gelation, future research should consider including other enzyme inhibitory agents in the presence of MTGase to improve the gel texture.
由鲶鱼副产物提取的蛋白质分离物制成的鱼糜状凝胶质地已被证明很脆且缺乏弹性。为了解决这个问题，使用了0.1至0.6单位/克不同水平的微生物转谷氨酰胺酶（MTGase）。MTGase对凝胶的颜色特征影响很小。当使用0.5单位/克的MTGase时，硬度、内聚性、弹性、咀嚼性、回复性、易碎性和变形分别增加了218%、55%、12%、451%、115%、446%和71%。MTGase添加量的进一步增加并未带来任何质地改善。与由鱼片碎末制成的凝胶相比，由蛋白质分离物制成的凝胶在内聚性方面仍然较低。由于内源性转谷氨酰胺酶的激活，一个凝固步骤增强了由鱼片碎末制成的凝胶的质地特性。然而，由于内源性蛋白酶引起的蛋白质降解，凝固步骤导致了由蛋白质分离物制成的凝胶的质地恶化。由蛋白质分离物制成的凝胶在还原溶液中的溶解度比在非还原溶液中高23 - 55%，这表明二硫键在凝胶化过程中起着至关重要的作用。由于蛋白质组成和构象不同，鱼片碎末和蛋白质分离物表现出不同的流变学特性。十二烷基硫酸钠 - 聚丙烯酰胺凝胶电泳（SDS - PAGE）显示，高度变性的蛋白质分离物在凝胶化过程中易受蛋白水解作用且易于形成二硫键。它还表明MTGase对内源酶诱导的蛋白水解有抑制作用。鉴于蛋白质分离物在凝胶化过程中易受蛋白水解作用，未来的研究应考虑在MTGase存在的情况下加入其他酶抑制剂以改善凝胶质地。
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