Postmortem changes in the freshness and volatile compounds of grass carp (Ctenopharyngodon idella)

Although grass carp is an important freshwater fish in the food industry, little is known about the changes that occur in its volatile components and its degree of freshness postmortem. These changes were, therefore, investigated in this study. including total volatile basic nitrogen (TVB-N), total viable counts (TVC), thiobarbituric acid-reactive (TBA) substances and lipase activity of the dorsal muscle of grass carp stored at 4 °C for postmortem up to 8 days. Volatile components were simultaneously quantified assessed using gas chromatography–mass spectrometry (GC–MS). Sensory assessment (SA) and electronic nose assessments were also performed. Results indicated that the level of TVB-N, TVC and TBA increased with storage time increase, reaching 16.92 mg/100 g, 5.37 log 10 CFU/g and 0.72 mg/100 g at 144 h, respectively. Lipase activity peaked on the first day of storage, and then began to decrease rapidly afterwards, reaching its minimum (34.76 ± 8.90 U/g prot) on the eighth day, suggesting the decrease in the freshness. While the SA had exceeded the acceptable limit by the sixth day. The number of volatile compounds increased with the prolongation of storage time. Relative olfactory activity value (ROAV) analysis showed that 9, 8, 8, 12, 12 and 9 predominant components were identified at 0 h, 24 h, 48 h, 96 h, 144 h and 192 h, respectively. The findings suggest that grass carp should be consumed within 6 days when stored at 4 °C, with the optimal edible time being 4 to 8 h after death.