This study investigated the effect of an ammonia nitrogen-reducing biofilm on the stress response and muscle quality of crucian carp (Carassius auratus) during high-density transportation. A control group and a treatment group (with ammonia nitrogen-reducing biofilm) were established, and multiple physiological and quality indicators were measured under simulated transportation conditions. The results showed that the biofilm significantly alleviated transportation stress, as evidenced by smaller increases in blood stress indicators (e.g., cortisol and glucose). Meanwhile, it reduced gill and liver damage, increased antioxidant enzyme activity, and decreased malondialdehyde (MDA) content. In terms of muscle quality, the treatment group exhibited lower drip loss and lactic acid content, higher shear force, pH, glycogen, and ATP levels, less color change, reduced cell apoptosis, more intact muscle tissue structure, and significantly improved survival rates. This study provides an effective technical reference for the high-density live transportation of freshwater fish.

This study simulated 12-hour transportation stress in mirror carp (Cyprinus carpio). Muscle samples from both the control and stressed groups were stored at 4 ℃ for 0, 1, 3, and 5 days. After steaming, the samples were analyzed using gas chromatography-mass spectrometry (GC-MS), high performance liquid chromatography (HPLC), and other techniques to investigate changes in flavor compounds and sensory attributes, aiming to elucidate the effect of transportation stress on the flavor quality of refrigerated mirror carp. The results showed that transportation stress significantly altered the composition of flavor compounds during refrigeration. Specifically, the levels of bitter amino acids, total free amino acids, total volatile compounds, and hexanal increased, whereas those of umami amino acids(glutamic acid) and organic acids (malic acid and lactic acid) decreased in the stressed group. Moreover, the content of the umami compound inosine monophosphate (IMP) significantly decreased from days 1 to 3 of refrigeration after stress, while that of the bitter compound hypoxanthine (Hx) significantly increased from days 1 to 5. Sensory evaluation scores for taste, odor, and overall acceptability were lower in the stressed group than in the control group and declined with prolonged storage. In summary, refrigeration led to flavor deterioration of mirror carp, and transportation stress exacerbated this process, characterized by an accelerated loss of umami compounds (glutamic acid and IMP) and an increase in bitter and undesirable volatile compounds, thereby significantly reducing the sensory acceptability of fish meat.