Steam-Microwave Cooking Improved Meat Tenderness of Stewed Tenderloin and Enhanced Perceived Saltiness and Umami of Broth by Promoting Unfolding and Degradation of Protein

The change in texture and broth taste characteristics of stewed pork tenderloin during the steam preheating combined with microwave cooking (SMC) treatment was investigated in comparison with microwave cooking (MC) and steam cooking (SC), focusing specifically on the alterations in myofibers’ structure and protein conformation. The results indicated that steam preheating treatment of SMC contributed to a more fully unfolded conformation of protein accompanied by a higher surface hydrophobicity and lower α-helix than MC in the first cooking stage, thereby weakening the shrinkage of myofibers and achieving a lower conversion of immobilized water to free water. In this case, a lower shear force and higher water retention of meat was achieved, which symbolized a higher meat tenderness. Moreover, the unfolded conformation of protein promoted its degradation into amino acids and the release of nucleotides from the meat into the broth, thus improving the perceived saltiness of broth prepared by SMC. Therefore, the unfolding of myofibrillar protein during SMC heating is the key to improve the tenderness of meat and perceived saltiness and umami of broth.