Effect of ice structuring protein on the microstructure and myofibrillar protein structure of mirror carp (Cyprinus carpio L.) induced by freeze-thaw processes

The cryoprotective effect of ice structuring protein (ISP) on the microstructure and myofibrillar protein (MP) structure of mirror carp induced by freeze-thaw (F-T) processes was surveyed. The average diameter of ice crystals of those without ISP increased (from 130 to 220 μm), and the carbonyl content and 2θ value were also increased, meanwhile, the sulfhydryl, free amine, α-helix content, fluorescence intensity (FI) and peak intensity were significantly decreased after five F-T processes (P < 0.05). When the addition of ISP, the size of ice crystal and the change in MP structure of ISP-treated sample was smaller than those without ISP in a single F-T period. The average diameter of ice crystals of ISP-treated sample was 17.5% lower than those without ISP after three F-T processes. The carbonyl content of ISP-treated sample was 16.5% lower than those without ISP after five F-T processes. The α-helix and FI of ISP-treated sample were 58.2% and 816 A.U., higher than those without ISP. The physical stability of the MP was increased after ISP treated. Hence, ISP could protect muscle fibers by inhibiting the extension of ice crystals, and improve the stability of the MP structure.