Lan Weiqing, Zhao Yanan, Gong Taoshuo, Mei Jun, Xie Jing
College of Food Science and Technology, Shanghai Ocean University, Shanghai, China.
Shanghai Aquatic Products Processing and Storage Engineering Technology Research Center, Shanghai, China.
J Food Biochem. 2021 Jun 21:e13826. doi: 10.1111/jfbc.13826.
The effects of five thawing methods (ultrasonic thawing [UT], radiofrequency thawing [RFT], water immersion thawing [WIT], microwave thawing [MT], and cold storage thawing [CST]) on physicochemical properties, water migration, and protein characteristic of whole frozen pompano (Trachinotus ovatus) were investigated and compared with fresh samples (FS). The physicochemical changes of thawed pompano were analyzed based on pH, total volatile basic nitrogen (TVB-N), color difference. The protein aggregation, physicochemical properties and conformation of myofibrillar proteins (MPs) were evaluated by Sodium dodecyl sulfate polyacrylamide gel electrophoresis, differential scanning calorimetry, and Raman spectra, respectively. Water migration and MPs microstructure were measured by low-field nuclear magnetic resonance (LF-NMR) and scanning electron microscope (SEM), respectively. The results showed that different thawing methods could accelerate the protein denaturation and decrease of quality in pompano, especially MT treatment causing more seriously local overheating phenomena. Among the samples with different thawing treatments, the changes of pH, TVB-N values, and color difference in RFT and UT were closed to that from FS. The MT had the shortest thawing time, but could produce the damage of structural muscle. RFT had desirable thermal stability and made the protein secondary structure more stable, the myofibril bundles were also straight and smooth by SEM observation. The content of bound water and free water had no significant changes by LF-NMR. Therefore, compared with other thawing methods, RFT is a desirable thawing method for maintaining the quality of thawed pompano. PRACTICAL APPLICATIONS: Before further processing of frozen pompano, the thawing process is an important part, which is highly associated with the quality of products. The damage of conformation and properties in aquatic protein caused by freeze-thaw process is very obvious in food processing industry. Compared to microwave thawing, ultrasonic thawing, and traditional methods, the radiofrequency thawing (RFT) could reduce changes in structure and properties of protein, and have higher thawing efficiency. The temperature distribution on the pompano surface was uniform during the radiofrequency process with higher strong penetration and less local overheating. The RFT is a desirable thawing method to maintain the quality and extend the shelf life of frozen pompano for application in food industry.
研究了五种解冻方法（超声解冻[UT]、射频解冻[RFT]、水浸解冻[WIT]、微波解冻[MT]和冷藏解冻[CST]）对整条冷冻卵形鲳鲹（Trachinotus ovatus）理化性质、水分迁移和蛋白质特性的影响，并与新鲜样品（FS）进行比较。基于pH值、总挥发性盐基氮（TVB-N）、色差分析解冻后卵形鲳鲹的理化变化。分别通过十二烷基硫酸钠聚丙烯酰胺凝胶电泳、差示扫描量热法和拉曼光谱评估肌原纤维蛋白（MPs）的蛋白质聚集、理化性质和构象。分别通过低场核磁共振（LF-NMR）和扫描电子显微镜（SEM）测定水分迁移和MPs微观结构。结果表明，不同解冻方法会加速卵形鲳鲹蛋白质变性和品质下降，尤其是MT处理会导致更严重的局部过热现象。在不同解冻处理的样品中，RFT和UT处理的pH值变化、TVB-N值变化和色差与FS样品接近。MT解冻时间最短，但会对肌肉结构造成损伤。RFT具有良好的热稳定性，使蛋白质二级结构更稳定，通过SEM观察肌原纤维束也笔直且光滑。LF-NMR分析表明结合水和自由水含量无显著变化。因此，与其他解冻方法相比，RFT是一种保持解冻后卵形鲳鲹品质的理想解冻方法。实际应用：在对冷冻卵形鲳鲹进行进一步加工之前，解冻过程是重要环节，与产品质量高度相关。在食品加工业中，冻融过程对水产蛋白质构象和性质的破坏非常明显。与微波解冻、超声解冻和传统方法相比，射频解冻（RFT）可以减少蛋白质结构和性质的变化，且解冻效率更高。射频解冻过程中卵形鲳鲹表面温度分布均匀，穿透性强，局部过热少。RFT是一种保持冷冻卵形鲳鲹品质并延长其货架期的理想解冻方法，可应用于食品工业。
