Dual cryoprotective and antioxidant effects of silver carp (Hypophthalmichthys molitrix) protein hydrolysates on unwashed surimi stored at conventional and ultra-low frozen temperatures
Xiaolei Shen, Ting Li, Xianghong Li, Faxiang Wang, Yongle Liu, Jinhong Wu
Abstract
The dual cryoprotective and antioxidant effects of silver carp hydrolysates on unwashed surimi, stored at conventional (−18 °C) or ultra-low (−60 °C) temperatures and subject to three and six freeze-thaw treatments, were examined. The addition of hydrolysates could alleviate the formation of carbonyls of myofibrillar protein, inhibit the decrease of free sulfhydryl content and keep the protein bands stability compared to the control and SuSo group. The lipid peroxidation product malondialdehyde, and the target volatiles hexanal, nonanal and 1-octen-3-ol of the unwashed surimi as detected by HS-SPME-GC-MS, increased slowly under the protection of hydrolysates. The oxidation for proteins and lipids in freeze-thawed samples stored at −18 °C are lower than those of samples stored at −60 °C (p < 0.05), indicating that ultra-low frozen temperature storage accompanied by freeze-thaw cycles accelerates structural deterioration of unwashed surimi. LF-NMR and SEM also revealed that the hydrolysates facilitated to form gel network with preferable structural integrity and stability during freeze-thaw treatments. This study provides theoretical supports for the application of silver carp protein hydrolysates as a cryoprotectant in transportation and storage of frozen surimi.