Effect Of Konjac Glucomannan With Different Degrees Of Deacetylation On Gel Properties Of Silver Carp Surimi

Surimi products are widely liked by consumers because of their high protein content,low fat content,delicate taste and other characteristics.With the increasing depletion of marine fish resources,freshwater fish resources with huge yields have gradually attracted people's attention.However,the gel properties of the freshwater fish surimi are inferior to those of marine fish surimi due to raw materials.In order to improve the quality of freshwater fish surimi products,researchers and producers have done a lot of work from production process to quality improver.It has been reported that Konjac glucomannan?KGM?can improve the quality of surimi products.KGM is a neutral plant polysaccharide with good gelation and solubility,and these properties are related to its acetyl group.It was believed that the removal of acetyl groups from KGM could affect the gel properties of surimi.However,there are few reports about the effect of the degree of removal of acetyl groups from KGM on the quality of surimi products,and the underlying mechanisms are still not clear.Therefore,the purpose of this study is to explore the effect of KGM with different degrees of deacetylation on the gel properties of silver carp surimi,and try to analyze the mechanisms,so as to broaden the application of KGM and provide a theoretical basis for producing high-quality freshwater fish surimi products.The main results were as follows:1.The effects of KGM with different degrees of deacetylation on gel properties of silver carp surimi.The changes of gel rate,rheological properties,gel strength,texture?TPA?characteristics and whiteness of silver carp surimi gels with the addition of KGM with different degrees of deacetylation?different addition amounts?were studied by rheometer,physical property meter and chromatic aberration instrument.The results showed that KGM decreased the gel rate and gel strength of surimi gels.With the increase of deacetylation degree,deacetylated konjac glucomannan?DKGM?significantly increased the gel rate and gel strength.KGM with different degrees of deacetylation decreased the elasticity and whiteness of surimi gels,but significantly increased the storage modulus and loss modulus of surimi dose-dependently,and enhanced the viscoelasticity of surimi gels.DKGM1,with half of the acetyl group from KGM removed,made the composite surimi have the best rheological properties.DKGM generally improved the hardness,viscosity and chewiness of the surimi gel in TPA characteristics.2.The effects of KGM with different degrees of deacetylation on the water state of silver carp surimi gels.The water holding capacity,relaxation time T₂ and microstructure of silver carp surimi gels with the addition of KGM with different degrees of deacetylation?different addition amounts?were studied by centrifugation,low-field nuclear magnetic resonance?LF-NMR?and scanning electron microscopy?SEM?.The results showed that KGM significantly increased the water holding capacity and T₂₂ peak area of surimi gels.However,KGM reduced the T₂₂ relaxation time and the mean pore size of the network structure.With the increase of deacetylation degree,the water holding capacity and T₂₂ peak area showed a downward trend.The T₂₂ relaxation time and the mean pore size of the network structure showed an upward trend.DKGM2,with all the acetyl group from KGM removed,made the water holding capacity of the surimi gels become the lowest,enhanced the mobility of the water and made the water excluded from the tissues.The network structure of the surimi gels with the addition of KGM with different degrees of deacetylation became more orderly,complete and compact.Especially,the spatial network structure of DKGM1 was the best.3.The effects of KGM with different degrees of deacetylation on protein property of silver carp surimi gel.The changes of protein composition,protein molecular interaction force and protein structure of silver carp surimi gels with the addition of KGM with different degrees of deacetylation?different addition amounts?were studied by electrophoresis,infrared spectroscopy and Raman spectroscopy.The results showed that KGM with different degrees of deacetylation,especially DKGM,changed the hydrophobic interaction and ionic bond of surimi gels,and reduced the hydrogen bond.KGM with different degrees of deacetylation did not significantly change the molecular weight of the myosin heavy chain?MHC?and actin in surimi protein.New characteristic absorption peaks of surimi protein were not observed and no characteristic absorption peaks disappeared.Raman spectroscopy results showed that KGM with different degrees of deacetylation promoted the transformation of?-helix structure into random coil structure,affected the hydrophobic interaction of protein molecules and promoted the formation of disulfide bonds,resulting in changes in protein conformation.The results showed that KGM with different degrees of deacetylation could change the relative speed of protein unfolding and aggregation by affecting the water state of the surimi gel,the secondary structure of the protein and the protein interaction force,especially the hydrophobic interaction,which affected gelation process of the surimi and ultimately change the macroscopic characteristics of the surimi gels.This is due to the difference of the ability of KGM to bind water,hydrophobic interaction,and gel stability,which was caused by the degree of acetyl group removal from KGM.The appropriate acetyl removal from KGM is more conducive to improving the gel properties of silver carp surimi.