Effects Of Vacuum And Salts On The Protein Structure And Gelling Properties Of Silver Carp Surimi

Surimi food is one kind of traditional aquatic products in China with a long history.It is popular with consumers due to its high protein content,low fat content,convenience,culture and so on.It increased the fastest in output among all of the aquatic products in the last decade.Chopping is one of the key steps in surimi products processing.It possess the functions in mixing the components uniformly and promoting the dissolution of myofibrillar protein in cooperation with salt.Chopping methods and conditions significantly influence gel properties of the surimi.Presently,researches reported mainly focuse on surimi gelation as affected by the chopping conditions(speed,time,temperature).It has been found that vacuum chopping could improve gel strength of the cod surimi.Vacuum chopping has been used widely in the processing of high-grade surimi products.However,the mechanism of the effects of vacuum chopping and salt under vacuum chopping on gelling properties of surimi(especially freshwater)is still not clearly.In this study silver carp surimi was used as raw material.And the effects of vacuum and salt concentration(sodium chloride and calcium chloride)under vacuum on silver carp surimi gelling properties were investigated in order to provide theoretical basis for high quality surimi products processing.The main research contents and results were as follows.1.Effects of vacuum degree on structure and gelling properties of silver carp myofibrillar protein were studied.Vacuum chopping showed significant influence on structural and gelation properties of the myofibrillar proteins.With the increase of the vacuum degree,diameter and number of air bubbles in the paste decreased after chopping,content of disulfide bonds of myofibrillar protein decreased significantly(p<0.05),while the surface hydrophobicity increased significantly(p<0.05).Breaking force and penetration distance increased significantly with the vacuum degree up to 0.06 MPa(p<0.05).Non-disulfide covalent bonds and hydrophobic interactions of surimi gel increased significantly with the vacuum degree(p<0.05).SEM results showed that the three-dimensional network structure became more compact and uniform under higher vacuum condition.Vacuum chopping could enhance the gel strength mainly be the mains of removing air bubbles in surimi paste,which inhibited the formation of disulfide bonds and promoted the explosive of protein hydrophobic groups,resulting in the enhancement of the interaction between protein molecules and the formation of ordered three-dimensional gel network.2.Effects of sodium chloride concentration on structural and gelling properties of silver carp myofibrillar protein under vacuum chopping conditions.Concentration of sodium chloride had significant influence on the surface hydrophobicity,disulfide bonds and gel properties of myofibrillar protein under different chopping methods.With the increase of sodium chloride concentration,diameter and number of air bubbles in surimi paste increased after chopping,content of disulfide bonds,surface hydrophobicity of myofibrillar protein and the water holding capacity of surimi gels increased significantly(p<0.05).Breaking force and penetration distance of surimi gel increased with the concentration up to 1% and then decreased(p<0.05).As compared with the atmospheric chopping,the diameter and number of air bubbles in surimi paste decreased after chopping.The disulfide bond content of myofibrillar proteins decreased(p<0.05),while the surface hydrophobicity of myofibrillar proteins increased(p<0.05),breaking force,penetration distance and water holding capacity of surimi gel increased(p<0.05).Additionly,whiteness of the surimi gel with the vacuum chopping decreased(p<0.05).Effect of sodium chloride concentration on myofibrillar protein structure and gel properties was the same regardless of chopping methods.Vacuum chopping inhibited the formation of disulfide and promoted the explosive of protein hydrophobic groups,resulted in increased gel strength.Results showed that the vacuum had no effect on the optimum concentration of sodium chloride.3.Effects of calcium chloride concentration structural and gelling properties of silver carp myofibrillar protein under vacuum chopping.Calcium chloride concentration had significance influence on silver carp myofibrillar protein structure and gelling properties.As the calcium chloride concentration increased,breaking force of surimi gels firstly increased and then decreased followed by increasing and then decreasing(p<0.05),while the penetration distance decreased(p<0.05)continiously.The breaking force of surimi gels showed higher values at the calcium chloride concentration of 20 mmol/kg and 40mmol/kg,which increased by 6.1% and 3.1%,respectively,compared with the surimi gel without calcium chloride addition.However,the calcium chloride concentration were 10mmol/kg and 30 mmol/kg under vacuum chopping,and increased by 10.5% and 6.1%,respectively.Results revealed that the optimal concentration of calcium chloride decreased under vacuum condition.Vacuum chopping promoted the explosive of protein hydrophobic groups of myofibrillar protein,which was beneficial to the covalent cross-linking of protein molecules.