Effects of immersion freezing on the conformational changes of myofibrillar proteins in pork under ultrasonic power densities of 0, 15, 30 and 45 W L-1

The objective of this study was to assess the effects of ultrasonic-assisted immersion freezing (UIF) of 0, 15, 30 and 45 W L-1 on the conformation changes of pork myofibrillar protein (MP). The structure and conformation of MP were evaluated, and the solubility, thermal stability and sodium dodecyl sulphate-polyacrylamide gel electrophoresis (SDS-PAGE) were also discussed. The sample treated with 30 W L-1 (UIF-30) had the highest total protein solubility (116.6 mg g(-1)) and thermal denaturation temperature (57.07celcius) compared with other treatments. UIF-30 has higher alpha-helix content, and fluorescence intensity together with surface hydrophobicity had insignificant changes compared with the control. In SDS-PAGE, only the sample treated with 45 W L-1 (UIF-45) showed slight band degradation. In general, UIF-30 effectively minimised the changes of protein conformation, which may be related to the reduction of mechanical damage to muscle cells caused by rapid freezing to form regular and uniform ice crystals. This is more conducive to reducing pork quality degradation caused by protein freeze denaturation.