Effective role of konjac oligosaccharide against oxidative changes in silver carp proteins during fluctuated frozen storage

Abstract

The aim of this research was to perform a comparative analysis of konjac oligosaccharides (KOG) and conventional cryoprotectant (4% sucrose + 4% sorbitol) mixture (positive control, PC) as an effective antioxidant during fluctuated (FLUC) frozen storage of silver carp proteins. The surimi proteins were added with PC, KOG (1%) and KOG (3%) and antioxidative abilities were analyzed during FLUC frozen storage. The Ca2+-ATPase, total and reactive sulfhydryl groups (SH) groups were significantly reduced in all samples due to denaturation of myosin globular head. The control (C) samples also showed increase in carbonyls from 29.36 to 49.11 nmol/mg during FLUC-I and from 29.81 to 46.09 nmol/mg during FLUC-II. Meanwhile, the PC sample and KOG (1 and 3%) significantly (P < 0.05) reduced the carbonyls and surface hydrophobicity by inhibiting the formation of disulfide bindings. The addition of KOG (3%) restricted the increase in surface hydrophobicity, decline in SH groups and Ca2+-ATPase than the PC and KOG (1%) added samples due to better and strong intermolecular interactions with protein molecules. Furthermore, KOG (3%) enhanced the gel strength of surimi by forming well-established and dense gel network of protein. Overall, KOG (3%) was found to be a potential substitute of PC for seafood frozen preservation and commercial benefits.