College of Life Science, Langfang Normal University, Langfang, P. R. China.
Hebei Key Laboratory of Animal Diversity, Langfang, P. R. China.
J Food Biochem. 2022 Oct;46(10):e14319. doi: 10.1111/jfbc.14319. Epub 2022 Jul 14.
Storing at -18°C, the surimi was processed from fresh grass carp, supplemented with pork backfat of 50, 100, or 150 g kg (groups F , F , F , and F , respectively). The surimi was thawed and refrozen weekly afterward, with changes in surimi protein structure (primary structure, secondary structure, and tertiary structure), protein oxidation index (carbonyl and sulfhydryl), lipid oxidation index (TBARS), protein solubility, as well as surimi quality (texture characteristics and whiteness), were determined. The results showed that the texture characteristics of surimi increased after the first freezing and thawing (F-T) cycle and then decreased. The whiteness of the surimi decreased with the increase of F-T cycle times, while the whiteness of the surimi increased with the increase in fat content. With the F-T cycle times and fat content rising, the relative content of α-helix structures, sulfhydryl content, and protein solubility decreased. In contrast, carbonyl content was in reverse, being an increasing trend. The free amino content showed a decrease after an increase at the early stage with the F-T cycles growing, while it showed a decrease with an increase in fat content. Meanwhile, the redshift in the maximum absorption peak of the tryptophan fluorescence was caused by the F-T cycles, so was the decline in fluorescence intensity; however, there was little difference in tryptophan spectra with the same fat content. The association among protein structure, protein oxidation, lipid oxidation and surimi quality were elucidated by Pearson's two-tailed correlation. The lipid oxidation in the repeated freezing and thawing process of surimi led to the decrease in whiteness. The protein oxidation led to the change of protein structure and the decrease of protein solubility. Lipid oxidation caused by the increase of fat content led to the decrease of free amino content and protein solubility, and finally led to the increase of whiteness and the deterioration of texture characteristics. PRACTICAL APPLICATIONS: In this study, changes in various components of surimi were measured to examine the interrelationship among protein structure, protein oxidation, lipid oxidation and surimi quality. Freeze-thaw cycle and high-fat content are easy to cause lipid oxidation, protein oxidation, a decrease in protein solubility, and deterioration of surimi quality. Therefore, temperature fluctuations must be avoided to extend the shelf life of such products. An appropriate fat content level must be selected to prevent protein and lipid oxidation and maintain quality.
在-18°C 下储存，该鱼糜由新鲜草鱼制成，分别添加 50、100 或 150 g kg 的猪背脂（分别为 F、F、F 和 F 组）。鱼糜解冻后每周进行一次再冷冻，鱼糜蛋白结构（一级结构、二级结构和三级结构）、蛋白氧化指数（羰基和巯基）、脂质氧化指数（TBARS）、蛋白溶解度以及鱼糜质量（质构特性和白度）发生变化。结果表明，在第一次冻融（F-T）循环后，鱼糜的质构特性增加，然后下降。鱼糜的白度随着 F-T 循环次数的增加而降低，而随着脂肪含量的增加而增加。随着 F-T 循环次数和脂肪含量的增加，α-螺旋结构的相对含量、巯基含量和蛋白质溶解度降低。相反，羰基含量呈上升趋势。随着 F-T 循环的增加，游离氨基酸含量先增加后减少，而随着脂肪含量的增加则减少。同时，色氨酸荧光最大吸收峰的红移是由于 F-T 循环引起的，荧光强度也随之下降；然而，在相同脂肪含量下，色氨酸光谱几乎没有差异。通过 Pearson 双侧相关分析，阐明了蛋白质结构、蛋白质氧化、脂质氧化与鱼糜质量之间的关系。在鱼糜反复冻融过程中，脂质氧化导致白度下降。蛋白质氧化导致蛋白质结构的变化和蛋白质溶解度的降低。脂肪含量增加导致游离氨基酸含量和蛋白质溶解度降低，最终导致白度增加和质构特性恶化。实际应用：在这项研究中，测量了鱼糜的各种成分变化，以检验蛋白质结构、蛋白质氧化、脂质氧化与鱼糜质量之间的相互关系。冻融循环和高脂肪含量容易导致脂质氧化、蛋白质氧化、蛋白质溶解度降低和鱼糜质量恶化。因此，必须避免温度波动以延长此类产品的保质期。必须选择适当的脂肪含量水平，以防止蛋白质和脂质氧化，保持质量。
