| Lateolabrax japonicus is an economical marine fish with high nutritional value.The surimi food has value due to the fish short shelf life.It could not only expand consumption ways,but also increase food diversity.Gallic acid can promote protein cross-linking and improve gel performance.Ultrasound technology can improve protein functional properties by changing protein structure.Thus,Lateolabrax japonicus was used as experimental object to systematically studies the effects of ultrasonic assisted by gallic acid on the physicochemical properties,protein structure and gel properties of Lateolabrax japonicus myofibrillar proteins.Meanwhile it provides theoretical support and technical guidance for production of the Lateolabrax japonicus industry.The results are as follows:1.The effect of different concentrations of gallic acid（0 mg/g,1mg/g,2 mg/g,4 mg/g,6 mg/g）combined with 400 W ultrasound on the physical and chemical properties of Lateolabrax japonicus myofibrillar protein was studied.The results showed that the particle size,total sulfhydryl and carbonyl content were significantly decreased（P<0.05）,the absolute value of the potential was increased,the Ca2+-ATPase activity was decreased,and the dimer tyrosine content was significantly reduced（P<0.05）.The ultrasound with gallic acid could slow down the oxidation of protein and made the protein solution system more stable.When the concentrations of gallic acid was 2 mg/g,the indexes of the protein solution were the most favorable.2.The effect of different concentrations of gallic acid combined with 400 W ultrasound on the structure of Lateolabrax japonicus myofibrillar protein was studied.The results showed that theα-helix content was increased,and the correspondingβ-sheet,β-turn and random curl content were reduced,and then the protein structure was changed.Fluorescence intensity was increased,and surface hydrophobicity was also significantly increased（P<0.05）.The thermal denaturation temperature of the protein was increased,then the protein thermal stability was enhanced.The results of the electrophoresis spectrum showed that the polyphenols could promoted protein to cross-link.The results of rheological properties showed that the storage modulus and the loss modulus were improved,and a more viscoelastic gel network structure was formed.Ultrasound can combine with gallic acid to change protein structure,promote protein cross-linking.Ultrasound has an auxiliary effect.3.The effect of different concentrations of gallic acid combined with 400 W ultrasound on the gel properties of Lateolabrax japonicus myofibrillar protein was studied.The results showed that the gel strength,hardness,chewiness and water holding capacity were significantly increased（P<0.05）,there were no significantly effect on the gel elasticity（P>0.05）,the cooking loss significantly decreased（P<0.05）.When the concentrations of gallic acid was 2 mg/g,the gel strength was maximum.At this time,the ratio of non-easy flowing water peak area was the highest,and the ratio of free water peak area was the lowest,the water solubility was highest and the cooking loss was lowest.The ultrasound group was generally better than the non-ultrasonic group.The protein aggregation and distribution behavior was improved.At the same time,the gel network structure of the protein treated with the concentrations of low gallic acid was compact. |
