酸溶条件及高强度超声波对鲢鱼肉分离蛋白的提取及凝胶特性的影响

研究了不同酸溶条件（鱼肉匀浆液的pH值）和高强度超声波（High Intensity Ultrasonic treatment, HIU）对酸溶等电点沉淀法鲢鱼肉分离蛋白（protein isolate, PI）的提取、蛋白组成以及凝胶特性的影响。数据显示：降低pH能显著提高蛋白回收率（由pH 4.0到3.0，提高了21.11%），但pH<3.0时，进一步降低pH对蛋白回收率不再有提高作用；HIU显著提高了蛋白回收率（pH 3.0时，提高了3.77%）；PI中以肌原纤维蛋白为主，pH降低能够显著减少等电点处可溶性中等分子蛋白种类及浓度，而HIU对此影响不大。pH降低和HIU均会增加PI凝胶亮度（89.24→94.25）和白度（83.24→88.45）。HIU显著提高了PI凝胶硬度（1531.74→1756.24 g），降低pH能够提高PI凝胶硬度（1162.55→1683.41 g），但当3.0后，作用不显著。pH低于4.0时，pH变化和HIU对PI凝胶弹性无显著影响（0.792~0.823）。降低pH和HIU引起PI凝胶蒸煮损失率的显著增加（2.05%→4.43%）。结论：极酸pH（pH<3.0）并不会提高蛋白回收率，且对PI凝胶特性无益。采用pH 3.0的酸溶条件并辅以HIU，能够得到最高的蛋白回收率及最优的PI凝胶特性。

Recovery and Gelation Property of Protein Isolate from Silver Carps (Hypophthal michthys molitrix) as Affected by pH and High Intensity Ultrasonic Treatment

Effects of Gradient acid pH and high intensity ultrasonic treatment (HIU) were combined with isoelectric solubilization/ precipitation (ISP) process on the extraction process, protein profile and functionality of the protein isolate (PI) from gutted silver carps without head were investigated. The pH reduction significantly raised the protein recovery of PI by 21.11% from pH 4.0 to 3.0, but further decrease did not affect any more. HIU could significantly increase the protein recovery by 3.77% at pH 3.0. PIs from all extraction combination methods were primarily composed of myofibril protein, and pH reduction significantly decreased the small molecular protein amount and type in supernatant of the 2nd centrifugation, but HIU showed little effect on it. The pH reduction or HIU increased the lightness (from 89.24 to 94.25) and whiteness (from 83.24 to 88.45) of PI gel. HIU significantly increased the PI gel hardness (from 1531.74 to 1756.24 g). The pH reduction from 4.0 to 3.0 elevated the gel hardness (from 1162.55 to 1683.41 g) significantly, but further decrease did not show any effect. The springiness of the PI gel decreased when solubilization pH decreased from 4.0 to 3.5, but further decease had no effect on this index (0.792~0.823), and HIU did not show any effect on it. The cooking loss of the PI gel increased significantly as solubilization pH decreasing and HIU aiding (from 2.05% to 4.43%). Conclusion: over acid pH (pH<3.0) did not increase the protein recovery and improve the gel property. Aided by HIU, highest protein recovery and best gel property could be obtained by solubilization of pH 3.0 in ISP process.