The Occurrence Mode And Small Size Effect Of Calcium In Nano-scaled Fish Bone During Gelling Of Sliver Carp Myosin

Silver carp(Hypophthalmichthys molitrix)is the primary freshwater fish in China and the output ranks second just after grass carp.Due to bilgy odor and intermuscular spines,silver carp is not popular in the fresh market.With white color and excellent elasticity of muscle,silver carp is widely used as a species for surimi production.Fish bone is the main solid by-product in fillet and surimi processing.It is rich in calcium,contains high nutritional value,has high bioavailability,and abundant source,also it is easy and cheap to obtain.Nano-scaled fish bone can improve the gel strength of silver carp surimi,but its mechanism is still unclear.With silver carp(Hypopthalmichthys molitrix)spine bone as the raw material to prepare different scales of fish bone,the response of physicochemical properties of micronized fish bones to temperature was investigated.Based on this,effects of nano-scaled fish bone on aggregation behavior and gel properties of fish myosin were investigated by using different occurrence modes of calcium and mirco-scaled fish bone as the control.Combined with physicochemical properties of micronized fish bone,effect of the small size of nano-scaled fish bone was explored.Meanwhile,occurrence modes and distribution of calcium were investigated during gelling of fish myosin.The intrinsic relationship between calcium occurrence mode and myosin gelation property was explored.Subsequently,the relative contribution to myosin gelation property was compared between the small size effect and occurrence mode of nano-scaled fish calcium.The aim was to provide the theoretical basis for promoting gel properties of myosin.The main conclusions of each chapter were summarized as follows:1.Effect of temperature on physicochemical properties of micronized fish bone was investigated.During heating,the calcium release rate of MFB and NFB increased(from0.69%to 2.21%and from 8.88%to 14.20%,respectively).Micronization could loosen natural structure of fish bone,which promoted the degradation of collagen and the calcium release during heating.The changes were beneficial for the decrease in the size of MFB,and they influenced each other.There was no significant change of the particle size of the NFB during heating,because it reached the minimum limit of size during nanocrystallization.The damaged structure increased the calcium release rate of NFB sharply up to 12 times as much as that of the MFB.The increased calcium release of the NFB during heating was closely related with the formation of collagen polypeptide calcium.In summary,the calcium release rate of micronized fish bone was intimately associated with particle size and structure of fish bone.The calcium release,degradation of collagen,and structural changes reacted on each other during heating.2.Effects of different occurrence modes of calcium on myosin gelling properties were investigated.The addition of calcium citrate promoted the alpha helix structure of myosin molecules changed into beta turn structure.Hydrophobic interaction and electrostatic interaction were the main forces for the formation of excellent gel network.The hydrophobic interaction,the electrostatic interaction and the ability to form disulfide bond became poor after the addition of HAP or TCP,which were not beneficial for the formation of good viscoelasticity of myosin.The viscosity of myosin assemblies together with three kinds of insoluble calcium salt(calcium citrate,HAP,TCP)decreased sharply with the increase of the shear rate,while Ca Cl₂ added led to the adverse result.Myosin with Ca Cl₂ exhibited the strongest viscoelasticity,and myosin with calcium citrate followed.However,the addition of HAP and TCP greatly reduced the viscoelasticity of myosin.In summary,adding ion or chelating peptide of calcium to myosin promoted the formation of gel network.HAP and TCP,the low calcium release rate,were interfered the gelling of myosin.3.The small size effect of calcium in nano-scaled fish bone during gelling of sliver carp myosin was investigated.The addition of NFB promoted the unfolding of the alpha helix structure of myosin molecules.The hydrophobic interaction was the main forces for the formation of excellent gel network.Adding MFB to myosin was not helpful for the unfolding of protein molecules and was not beneficial for the formation of intermolecular interaction,such as hydrophobic interaction and disulfide bond.In static rheological tests,the myosin solution added with NFB exhibited the characteristics of pseudoplastic fluid and the viscoelasticity ranked second after the myosin with Ca Cl₂.In dynamic rheological test,the further increase of calcium release of NFB boosted G'dramatically by increasing the temperature from 80 ^oC to 90 ^oC.At 90 ^oC,the G?of myosin with NFB was equivalent to the G'of the myosin with Ca Cl₂.The G?and G??of myosin gel network continually increased during the cooling process.The viscoelastic properties of myosin could be maintained well during frequency scanning.In micro-rheological test,the viscoelasticity of MFB myosin was higher than other samples.4.The occurrence mode of calcium in nano-scaled fish bone during gelling of sliver carp myosin was investigated.For the myosin added with NFB,the content of calcium ion increased from 1.65%to 2.16%after heated at 40 ^oC for 60min,and then the content decreased to 1.77%after heated at 90 ^oC for 360min.Heating promoted the release of large quantity of fish bone calcium into myosin solution,which was advantageous to boost the crosslinking of the myosin molecule and the calcium ion itself was changed into calcium binding myosin.Along with the process of heating,the calcium distribution became more uniform and compact.Heating boosted the information of orderly compact network structure of myosin.Particularly,the network structure of myosin with NFB was more uniform and dense than the control after 90 ^oC heating.Calcium affected the interreaction between water molecules and proteins,so as to change the distribution of water.During the heating,the moderately difficult flowing water from myosin added with NFB could be gradually transformed into free water and immobile water.This change especially occurred after heated at 90 ^oC for 30 min,resulting in the myosin network structure becoming compact and dense.In a word,heating promoted the calcium release of NFB and the calicum uniform distribution.Then the moderately difficult flowing water from myosin was gradually transformed into free water and immobile water.Those changes were helpful to form highly dense and uniform gel.