Effect Of Amino Acids On The Thermal Aggregation Of Myosin From Bighead Carp (Aristichthys Nobilis) In Different Salt Concentrations

The surimi and its products with high protein,high nutrition,low fat and other characteristics,by the vast number of consumers.Due to the scarcity of marine fish resources,freshwater fish have attracted much attention as raw fish for surimi.At present,the silver carp has been successfully developed as raw fish for freshwater surimi.Surimi products are usually high salt content,adverse effects on the body such as high blood pressure,cardiovascular disease.Traditional surimi products with good elasticity,hardness,chew resistance,not suitable for the elderly and children’s consumption.Therefore,it is more and more important to reduce the salt content of surimi products and to develop surimi products suitable for the needs of special populations.Amino acids as a small molecule additives,has been widely used in food and medicine and other fields.In this paper,we studied the effects and the mechanism of glutamate(Glu),cysteine(L-Cys)and lysine(L-Lys)histidine on the thermal assembling behavior.The effects of glutamic acid(Glu)and lysine(L-Lys)on the Young’s modulus of myosin,the gel properties and the microstructure were investigated under different heat-induced and salt contents.It provides a theoretical basis for the development of new surimi gel products with low salt and special populations.The main research contents and results are as follows:1.Glu,L-Cys,L-Lys and L-His on the heat-induced aggregation behavior of the carp myosin under different ionic strength.The two-dimensional and three-dimensional scans of different samples were obtained by atomic force microscopy(AFM)technique.The height map of myosin aggregates was obtained and the effects of different amino acids on the surface morphology of myosin solution was investigated.The results showed that Glu,L-Cys,L-Lys and L-His could change the surface morphology of myosin and affect the aggregation behavior of myosin.The big protein aggregates dispersed into more and smaller uniform aggregates,to ease its aggregation behavior,so that the more orderly aggregation behavior occurs.Especially in the low salt conditions,although the height of the aggregates decreases,the cross-linking in the transverse direction increasessignificantly.This helps to avoid the formation of large holes,forming a good gel network structure.2.Glu,L-Cys,L-Lys and L-His on the physicochemical properties of the carp myosin in different ionic strength treatments.The effect of Glu and L-Lys on the secondary structure and Young’s Modulus of myosin under different treatment conditions.The effects of different amino acids on the secondary structure,surface hydrophobicity,solubility and Young’s modulus of myosin were studied by circular dichroism,fluorescence spectrophotometer,UV-vis spectrophotometer and atomic force microscopy.The results showed that the addition of Glu,L-Cys,L-Lys and L-His significantly affected the surface hydrophobicity of myosin under high / low salt conditions.Induced by one-step heating,the amino acids significantly eased the aggregation of myosin.When induced by two-step heating and pre-heated,the effect of heating mode on myosin surface hydrophobicity was greater than that of amino acids;the solubility of myosin under low salt conditions was significantly increased.The effect of myosin solubility is the result of a combination of multiple factors;promotion of myosin expansion leads to a significant decrease in α-helix content;Theα-helix content lower than that high salt with or without addition of amino acids.The relationship between the changes of Young’s modulus and the evaluation of surimi gel properties needs further study.3.Effects of Glu and L-Lys on the gel properties and gel microstructure of silver carp surimi.The effects of different amino acids on TPA properties,gel strength,water retention and gel microstructure of silver carp surimi were studied by means of food property analyzer,centrifugation and scanning electron microscopy.The results showed that Glu and L-Lys could significantly increase the water retention of surimi gel and partially alter the texture properties of surimi gel under two-step heating and low salt conditions.In the two-step heating,Glu or L-Lys had no significant effect on the elasticity of the surimi gel under the two salt concentrations;Glu and L-Lys significantly reduced surimi Gel gel strength,forming a low hardness,low gel strength,but with good flexibility of the unique soft gel;surimi gel microstructure hasundergone significant changes,especially under low salt conditions,orderly three-dimensional network structure appeared,the mesh is small and uniform,easier to retain moisture than without.However,the network structure is slightly loose than higher salt conditions,leading to a decrease in gel strength and hardness,resulting in a soft gel.The results showed that Glu,L-Cys,L-Lys and L-His could interact with myosin by electrostatic interaction to occupy myosin hydrophobic binding site,induce myosin expansion,increase myosin solubility.Thus affecting its degeneration and thermal aggregation process,the final impact surimi gel properties.At the same time,due to the differences in the charged states and structures of the four amino acids,there is a difference in the degree of influence on the heat aggregation behavior and the gel properties of the proteins.