Mechanisms Underlying Tenderness Evolution in Pan-Fried Pork: Protein Conformational Shifts, Water Redistribution and Microstructural Reorganization

• The effect and cause of pan-frying on the shear force of pork lean were investigated • Moisture, protein conformation, and microstructure affected the texture of pork belly • Connective tissue gelation and dissolution mainly impacted pork shear force early on • Structure shrinkage and decreased water content raised shear force in later heating Pan-frying is a widely favored traditional cooking method for pork in China. However, the absence of a robust theoretical framework and scientific guidance has limited the systematic advancement of pan-fried pork production. In this study, the dynamic changes in shear force during pan-frying of lean pork belly were monitored, and the main influencing factors were explored in terms of water migration, protein conformation, and microstructure. During the initial heating stage, thermal denaturation of connective tissue proteins and unfolding of myofibrillar proteins disrupted the fibrous framework, leading to a marked decrease in shear force (from 117.70 N to 61.02 N). With continued heating to a core temperature of 107 °C, denatured myofibrillar and collagen proteins formed an elastic three-dimensional gel network that retained water and enhanced structural uniformity, further reducing shear force to 25.51 N. In the later stage, as the core temperature rose to 140-150 °C, pronounced myofibrillar contraction and water loss (55.74%) increased structural density, resulting in a partial rebound of shear force (from 25.51 N to 36.80 N). These results indicate that dynamic changes in protein conformation, microstructure, and water distribution ultimately govern pork tenderness during pan-frying. Furthermore, optimizing the balance between heating time and temperature, by promoting gel network formation near 100-110°C while minimizing exposure above 140 °C, can effectively reduce late-stage toughness while preserving the desired elastic texture of lean pork belly.