The effects of different inoculation methods of two dominant spoilage bacteria on the quality change in obscure pufferfish (Takifugu obscurus) during cold storage and their spoilage ability were evaluated. Sterile whole fish were inoculated with Pseudomonas fluorescens, Shewanella putrefaciens, or their combination. Samples treated with sterile water were taken as the control group. All samples were stored at 4 ℃. Microbial (total viable count, Pseudomonas bacteria count, and Shewanella bacteria count), physiochemical (pH, total volatile base nitrogen (TVB-N)) contents, K value, and xanthineoxidase (XOD) activity), and protein properties (total sulfhydryl (SH) content, myofibril fragmentation index (MFI), and intrinsic fluorescence intensity (IFI)) were measured at 2-day intervals during storage, and magnetic resonance imaging (MRI) was also carried out to analyze quality changes comprehensively. The spoilage ability of the dominant spoilage bacteria was evaluated by the yield factor of spoilage metabolite production. The results showed that total viable count, TVB-N contents and K value in the inoculation groups were higher than those of the control group. Inoculation with the spoilage bacteria accelerated protein oxidation and promote the breakage of myofibril, resulting in changes in the tertiary structure of fish proteins and a significant decrease in water content. Moreover, the rate of quality deterioration in the combined inoculation group was faster than that in the single inoculation groups. According to the results of the yield factor of spoilage metabolite production, the combined inoculum had the strongest spoilage ability, followed by S. putrefaciens, and P. fluorescens had the weakest spoilage ability.

In order to investigate the combined effects of ultrasound and slightly acidic electrolyzed water on the quality changes of vacuum-packaged sea bass (Lateolabrax japonicas) during refrigerated storage, fresh sea bass fillets were treated with ultrasonic (US) at 20 kHz and 600 W, slightly acidic electrolyzed water (SAEW), their combination (US + SAEW), or sterile water (as control) for 10 min and then stored in a refrigerator at 4 ℃. Total viable count (TVC), Psychrobacter count (PC), and physicochemical properties such as pH, total volatile base nitrogen (TVB-N) content, water migration, waterholding capacity (WHC)) and indicators lipid oxidation were measured every three days during storage. The results showed that the US and SAEW treatments inhibited the increase in TVC and PC during storage, and obviously slowed down the increase in pH and TVB-N content as compared to the control group. The US treatment greatly improved WHC. The SAEW treatment inhibited lipid oxidation in fish while improving WHC. Compared to the control group, the combined treatment provided the best quality preservation, and extended the shelf-life of refrigerated vacuum-packed sea bass by 6 days at least.