Study On The Processing Properties Of The Greater Lizardfish(Surida Tumbil) Surimi And The Effect Of Ultra-high Pressure Combined With Microbial Transglutaminase Treatment On The Gel Properties And Its Mechanism

Greater lizardfish?Surida tumbil?is a yield rich low-value surimi resource.But its intensive processing is very limited,mainly the fish meal or animal and plant feed,which is low-value products.The best way for utilization is processing to surimi.But there is a dehydration problem during processing and it has a poor gel properties.Microbial transglutaminase?MTGase?has a unique role on the quality of meat products.Ultra-high pressure has a unique physical modification for proteins and other biological macromolecules.Study on the processing properties and the effect of MTGase combined with ultra-high pressure treatment on its gel propertis and the mechanismis useful for industry.Based on the analysis,the processing properties which include dehydration conditions,frozen storage stability and basic gelling properties of greater lizardfish were investigated.The possible gelling mechanism of surimi gels induced by MTGase and ultra-high pressure were further studied.The main findings represented as follows.1.Studys on the rinsing conditions.The effects of different rinsing conditions?rinsing media,rinsing times?on gel properties of surimi were investigated by detecting the gel strength,texture,color and water holding capacity of greater lizardfish gels.And the optimum rinsing conditions were determined by orthogonal experiments Results shows that with the increasing concentration of CaCl₂ solution,sodium citrate concentration and rinsing times,the gel strength and elasticity of the gels firstly increased then decreased.High concentration of calcium chloride can improve the whiteness of the fish,but result in its poor texture,water holding capacity;with theconcentration of sodium citrate changed,texture and color changed little;with the increasing rinsing time,the gel texture decreased and the whiteness of gel increased.The orthogonal experimental results showed that the concentration of calcium chloride was the most effective factor on the quality of surimi gel,followed by rinsing times,and the last was the concentration of sodium citrate.The confirmatory experiments results showed that the optimum conditions were 0.3%calcium chloride and 0.1%sodium citrate.At this time,the surimi gel strength was 1268.31 g·cm,which has reached the national standard SSA grade??700g·cm?and the moisture content was 71.65%.It showed that the freshly suitable condition rinsed lizardfish gel exhibited a better gel properties.2.Studys on the storage stability of lizardfish surimi.The gel characteristics of greater lizardfish stored at-18?during different time were determined by gel strength,texture,color and water-holding capacity.The changes of physicochemical propertiesof natural actomyosin?NAM?during different storagetimewere studied by testingCa²⁺-ATPase activity,the content of total and surface active sulfhydryl and surface hydrophobicity.It showed that the storage stability of greater lizardfish was bad.The gel strength decreased by 52.18%and the water holding capacity decreased by 30.65%at the end of frozen storage?stored at-18?for 21 days?.The gel strength was significantly lower than the national standard?level B<100g·cm?.The activity of Ca²⁺-ATPase decreased by 57.86%.The content of total sulfhydryl and surface active sulfhydryl decreasedby 70.83%,67.76%respectively.The surface hydrophobicity increased by76%as the storage timeincreasing.Results showed that gel properties changed significantly with the prolongation of frozen storage time.The protein suffered a significant denaturation.3.Studys on thegel-formed conditions.Effect of different gel-formed conditions?temperature and time?on the gelling properties of gels from greater lizardfish surimi,about thetexture profile analysis were investigated.And the TCA-soluble peptide content,SDS-PAGE,solubility in different solvents were detected to illustrate the possible mechanisms.According to the result,the temperature and time of gel formed had a great imfluence on gel quality,and the optimal condition was 25?for 4h.The gel strength was 583.42g*cm.The activity of endogenous cathepsin at 40?was higher than that at25?,thus resulting in deterioration of the gel,also a decrease in gel strength.SDS-PAGE showed that the protein was crosslinked to form macromolecules at 25?,and the effect of cathepsin decomposition was more than that of the cross-linking at 40?.The disulfide bond and the hydrophobic interaction co-dominate the gel structure at25?,which is dominated by the weak hydrogen bond at 40?.4.Studys on the effect of lizardfish surimi gel properties.The influence of MTGase?enzyme activity unit was 304.2 mu/g?treatment,ultra high pressure treatment and the combination of MTGase and ultra high pressure treatment on the gel characteristics was studied by detecting texture characterastics.The results showed that the optimum addition amount of MTGaseand the effect time could promote a better water holding capacity?WHC?of surimi,but exhibited a poor color.The optimum addition amount of MTGase was 0.8%,the optimum temperature and time were 30?/1h.The gel strength was 245.59g.cm,which was 3.26 times of the control.High pressure treatment could promote to form gels and the WHC was better than heating treatment.But under 400MPa,the breaking force was no significantly different compared with heating treatment.The whiteness of high pressure treatment were all lower than heating treatment.The best ultra high pressure treatment condition was 500 MPa/15min.The gel strength was 216.33 g.cm,which was 1.31 times higher than control.The optimum conditions for the combination treatment of MTGase and ultra high pressure treatment were that the addition of 0.8%MTGase at 200 MPa for 45 min.The gel strength of surimi was 920.82 g.cm?national standard SSA grade?700g·cm?.It indicated that MTGase combined with high pressure treatment could reduce the pressure level of high pressure treatment alone,and the quality of the obtained gel was better.5.Studys on the mechanism of the lizardfish surimi gel properties.Effect of MTGase combained with ultra-high pressures and heat treatment on the gelling properties,TCA-soluble peptides content,the total thiol content,the solubility in different solvents,SDS-PAGE,Raman spectroscopy and Scanning electron microscopy of gels from greater lizardfish surimi were investigated.The results showed that after the addition of MTGase,the setting treatment before high pressure treatment could significantly improve the ge l strength of surimi?P<0.05?,promoting the formation of a smooth and orderly striped fiber lamellar structure.Setting treatment made MTGase accessible to the target and promoted to form non-disulfide covalent bonds.Hydrophobic interaction dominated in high pressure treatment.More hydrogen bonds formed during setting prior to high pressure.Heating treatment promoted to form more disulfide bonds.MTGase combined with high pressure treatment could change the secondary structure of the protein,so that the degree of cross-linking of covalent bonds increased.The solid structure of the gel was strengthened by the combined treatment.The internal structure of the gel was stable and had less flow units than heating treatment.