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