Abstract:This study investigated the quality changes in the abdomen muscle， cheliped muscle， and hepatopancreas of Portunus trituberculatus in different initial states [live crab （LC）， half-dead crab （HDC）， and dead crab（DC） before storage] during frozen storage at -20 ℃. Analyses were conducted on various indicators， including water-soluble protein content， serine protease activity， and myofibrillar protein active sulfhydryl group content， to assess the quality and flavor changes in the three crab states during storage. The results revealed that during -20 ℃ frozen storage， the water-soluble protein content， serine protease activity， myofibrillar protein active sulfhydryl group content， amino acid nitrogen content， glucose content， and tryptamine content exhibited a declining trend， with the degree of decline ranked as DC>HDC>LC. Trimethylamine（TMA） content， tyramine content， and putrescine content increased， with the degree of increase ranked as DC>HDC>LC. Lactate content initially increased and then decreased， with the overall content ranked as DC>HDC>LC during frozen storage. Serine protease activity in the hepatopancreas of all three crab groups decreased over time， while in the abdomen muscle， it initially decreased and then increased. The extent of serine protease activity variation was ranked as DC>HDC>LC. Nucleotide analysis indicated that the degree of flavor and quality deterioration was the highest in DC， followed by HDC， and the lowest in LC. In summary， during -20 ℃ frozen storage， the quality of the abdomen muscle and cheliped muscle in all three crab groups gradually deteriorated over time. LC exhibited the least degree of deterioration， while DC showed the most significant deterioration.