The effects of freshwater immersion on muscle qualities and the evaluation of water addition in Amphioctopus fangsiao (Mollusca: Cephalopoda) from the seafood market.

Amphioctopus fangsiao is widely favored by Asian consumers for its high nutritional value and delicious taste, yet fraudulent water addition practices often dissatisfy consumers. This study evaluated its nutritional value, established baseline data for the moisture (80.33 ± 5.28 g/100 g) and protein content (16.47 ± 2.95 g/100 g) of raw samples, and elucidated the effects of freshwater immersion. The muscle of A. fangsiao contained abundant taurine. However, freshwater immersion stress increased the octopus's weight, with 5-h exposure identified as a critical point for weight change. Moreover, it induced severe oxidative stress, enhanced protein oxidation, and disrupted metabolites related to amino acid metabolism and glycolysis, thereby deteriorating key muscle quality indices, including pH level, water-holding capacity, and texture. Based on the baseline data, we further investigated and assessed water addition practices in market samples, highlighting the need to strengthen market supervision.