Effect of Two-stage Heating on the Quality and Myofibrillar Protein Structure of Sterilized Prepared Pork Slices

The traditional high-temperature sterilization process often leads to deteriorated texture and reduced water-holding capacity (WHC) in prepared meat products. To improve the processing quality of prepared pork slices, a two-stage heating method was employed, in which a low-temperature preheating step (45~60 °C for 1~3 h) was introduced before high-temperature sterilization at 121 °C. Conventional heating (100 °C for 30 min followed by 121 °C for 5 min) was used as the control. The shear force, centrifugal loss, free-water mobility, and myofibrillar fragmentation index (MFI) of the pork slices were determined, together with the total sulfhydryl content, surface hydrophobicity, α-helical content, and intrinsic fluorescence intensity of myofibrillar proteins. Changes in protein band patterns were also examined using sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE), and Pearson correlation analysis was performed between the major quality attributes and protein-related parameters. Compared with the conventional heating control, the two-stage heating treatments resulted in lower shear force, centrifugal loss, free-water mobility, and MFI, as well as higher α-helical content, total sulfhydryl content, and intrinsic fluorescence intensity. Among the two-stage heating treatments, preheating at 55 °C for 2 h resulted in the lowest shear force, centrifugal loss, and MFI. SDS-PAGE patterns showed that the actin bands in the low-temperature preheated groups were more distinct than those in the control group. Surface hydrophobicity was significantly higher in the low-temperature preheated groups than in the control group (P<0.05). Pearson correlation analysis showed significant positive correlations among shear force, centrifugal loss, and MFI (P<0.01), whereas MFI was significantly negatively correlated with total sulfhydryl content (P<0.05). Under the experimental conditions used in this study, the treatment involving preheating at 55 °C for 2 h exhibited relatively favorable overall quality characteristics. These findings demonstrate that two-stage heating can improve the tenderness and water-holding capacity of prepared pork slices and provide a reference for its application in the processing of prepared meat products.