Thermal stability of actin of silver carp (Hypophthalmichthys molitrix) harvested in summer and winter as affected by myosin complexation

Thermal stability of silver carp actin in summer and winter as well as the effect of myosin binding was investigated. Actin denaturation was detected by chymotryptic digestion with 1/200 (w/w) of myofibrillar protein (Mf). The temperature heated for 30 min and reached 50% denaturation (T_1/2) of actin was 47°C for summer and 42°C for winter at 0.1 M salt concentration. Denaturation rate of winter actin was eight, six, four, and three times more quickly than summer one under 42, 43, 45, and 48°C, respectively. T_1/2 changed to 43°C for summer and 37°C for winter at 0.5 M salt concentration. With the rise of salt concentration from 0.1 to 2.0 M, the actin denaturation rate increased 10 ~ 60 times, but the difference between the two seasons disappeared above 1.5 M NaCl. T_1/2 for both summer and winter actin fell to around 40°C when actin was separated from myosin by adding magnesium pyrophosphates (Mg-PPi). Denaturation rate was promoted by 3 ~ 8 times with Mg-PPi higher than that without it, besides actin in summer and winter showed similar denaturation rate. It could conclude that the difference in thermal stability of actin depends on the stability of myosin when binding together. Summer and winter actin in silver carp Mf showed similar thermal stability after being separated from myosin. Novelty impact statement: The differences in thermal stability of silver carp actin in winter and summer were studied for the first time. The interaction between myosin and actin under different conditions was studied by changing the salt concentrations, adding Mg-PPi, etc. It simulated the actual manufacturing of surimi products to some extent. Understanding seasonal changes in actin stability will help food processors in thermal processing design to produce textured fish meat products based on the raw materials harvested.