Quality and Flavor Changes of Bonito Back Meat during Steaming

The changes of quality and flavor of bonito back meat during steaming were analyzed by mass loss rate, pH, texture, the content of myofibrillar protein and sarcoplasmic protein, moisture distribution, the content of free amino acid and volatile flavor substances and sensory evaluation. The results showed that the mass loss rate increased rapidly from 0 to 6 min and then stabilized, while the pH increased as a whole. The hardness showed two peaks. The elasticity reached 2.20 mm when steaming for 8 min, the content of myofibrillar protein and sarcoplasmic protein decreased significantly (P<0.05) from 0 to 6 min and then stabilized. The content of bound water decreased continuously, while the content of free water increased and then decreased. Overall, the content of glutamic acid and total free amino acid showed the same trend, which increased first and then decreased with steaming time. Steaming for 6 min and 8 min, the total amount of free amino acid up to 3369.03 and 3438.76 mg/100 g, respectively. The results of GC-MS (Gas Chromatography-Mass Spectrometry) showed that the relative content of heptanal and nonanal decreased gradually during the steaming process, which possessed fish flavor, and the contents of the above aldehydes were only 1.14% and 1.69% after steaming for 8 min, respectively. Moreover, sensory evaluation showed that the overall score was the highest when steaming for 8 min. Therefore, the quality and flavor of bonito pieces were the best for steaming 6~8 min.