| Among the many countries that farm tilapia in the world,China has become the largest producer and exporter of tilapia by relying on its resource advantage.Due to the influence of the new crown epidemic and trade friction,the tilapia industry in Hainan Province has reached a steady state.Therefore,for the better development of tilapia industry,it is important to master the freezing state of aquatic products,reasonably design the freezing process,control the quality of frozen products and establish a new method to evaluate the quality of tilapia fillets.In this study,we introduced the fractal dimension(FD)to quantify the damage of ice crystals to the microstructure,and established the correlation between the microstructural fractal dimension and the quality change of tilapia fillets.The method of microstructure fractal dimension as a method to evaluate the quality changes of tilapia fillets under different storage conditions was improved to provide technical support for the application of tilapia production and processing.The conclusions of the study are as follows.(1)For the observation method of muscle microstructure of tilapia fillets under different freezing and storage times,the advantages of short sample pre-treatment time and high efficiency of frozen section method were investigated,and the microstructure fractal dimension was obtained by using the cross-section of tilapia fillets,and the fractal dimension of the cross-section of fish fillets under different freezing and storage times was significant(P<0.05),so the fractal dimension of the cross-section of fish tissue could be used to quantify the damage of ice crystals on muscle tissue Therefore,the fractal dimension of fish tissue cross-sections can be used to quantify the extent of ice crystal damage to muscle tissue and provide a specific method to obtain the fractal dimension of microstructure for subsequent experiments.(2)Due to the influence of freeze-thaw cycles,ice crystals kept melting and freezing,resulting in the degradation of fish fillet quality,and with the increase of freeze-thaw times,the fractal dimension gradually became smaller and the damage of muscle microstructure increased.It was shown that the changes of microstructural fractal dimension of fish fillets during freeze-thaw were significantly correlated with quality parameters.The fractal dimension can be used in the quality evaluation of tilapia fillets,which can better reveal the changes of microstructure and is a novel quality index.(3)After the addition of antifreeze treatment,it can significantly prolong the time of maximum ice crystal generation zone of tilapia fillets,inhibit the increase of microstructural pores,slow down the decrease of microstructural fractal dimension,and is more favorable to maintain the integrity of muscle microstructure of tilapia fillets,and the effect of compound antifreeze group is the best.It was found that the compound use of algal sugar and polyphosphate could be used as an excellent anti-freeze protectant for tilapia fillets,which could effectively inhibit the growth of ice crystals inside the fillets,reduce the degree of muscle destruction,effectively resist freezing and retain water,and guarantee the quality of frozen tilapia fillets.(4)Tilapia fillets will decrease in color,texture and freshness with the increase of storage time,and the microstructure fractal dimension also shows a decreasing trend,so the size of microstructure fractal dimension of tilapia fillets can represent the quality of the fillets.The microstructural fractal dimension of tilapia fillets was measured to classify and evaluate the freshness of the fillets.The results showed that the fractal dimension was strongly correlated with T22,hardness,chewiness and L value,and a functional correlation model was established with correlation coefficients greater than 0.9. |
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