Abstract：Myofibril-bound serine protease (MBSP) was isolated from the back muscle of grass carp (Ctenopharyngodon idellus), and the pattern of seasonal variations in its enzymatic characteristic was studied. The results showed that the optimal saturation level of ammonium sulfate for enriching MBSP was 30%–60%. The optimal temperature for MBSP from winter and summer grass carps was 40 and 45 ℃, and the optimal pH was 8.0 and 9.0, respectively. After incubation at 60 ℃ for 30 min, more than 50% of the enzyme activity remained, demonstrating good thermal stability (P < 0.05). The enzyme activity could be inhibited by Na+ (0–40 g/L) and activated by 5.0 mmol/L K+ and Ca2+ (P < 0.05). However, compared to summer MBSP, winter MBSP exhibited lower enzymatic activity at medium-to-high temperatures (≥ 45 ℃) and under weakly acidic and alkaline conditions, as well as lower heat stability. Additionally, the activation of winter MBSP by metal ions was less pronounced under the same metal ion concentration conditions. This study provides molecular insights into seasonal variation in the gel quality of grass carp surimi and offers a theoretical basis for the development of differentiated strategies of temperature control, pH adjustment and ion addition for raw materials harvested in different seasons.
2026, Vol. 40 
