Texture Properties Of Tilapia Surimi And Comprehensive Utilization By Processing

Tilapia is delicious, nutritious, highly valued and popular among consumers. Inthis paper, tilapia was chosen as materials and the following researches were carriedout.1. The changes of gel strength and quality of tilapia surimi were investigated inthe process of rinsing. The dehydration rate, whiteness, curvature and gel strength ofrinsed surimi were analysised. The results showed that three types of salt solutions,0.25%sodium chloride,0.1%calcium chloride and0.4%potassium bicarbonate,significantly reduced dehydration rate and improved whiteness, curvature, gelstrength of surimi, especially0.25%salt solution and0.1%calcium chloride.2. The changes of gel strength and texture properties of Tilapia surimi werestudied by addition of different improvers. The index includes dehydration rate, tissuestructure, rheological characteristic parameters （elastic modulus E, stress relaxationtime τ, viscous modulus η, and gel strength）, Texture Profile Analysis parameters, andsensory evaluation. The single factor experiment was done by adding three improvers（Corn starch, TGase, Carrageenan） and then the orthogonal was carried out. Thesingle factor experiment showed that the three improvers made gel network structuremore compact and pores between fibrous tissue smaller. The presence of corn starchand TGase significantly increased elastic modulus（E₀、E₁、E₂）, viscous modulus（η₁、η₂）, and gel strength but the changes of relaxation time（τ₁、τ₂）were not notable. Theaddition of carrageenan in the surimi led to a significant increase in relaxationtime（τ1）, viscous modulus（η₁、η₂）, and gel strength but its impact on elasticmodulus（E₀、E₁、E₂） was not remarkable. It was concluded that certain relevanceexisted between tissue structure and rheological characteristic parameters. The TPAand sensory evaluation indicated that the surimi obtained comparatively good gelstrength, cohesiveness, gumminess and chewiness by adding8.0%corn starch,0.3% TGase, or0.05%carrageenan. The three improvers decreased the dehydration rate ofTilapia surimi especially corn starch and carrageenan, however, the addition of TGasedid not show significant changes on dehydration rate. Orthogonal test showed that thecomposite incorporation of8.0%corn starch,0.3%TGase, and0.075%carrageenanresulted in a decrease in dehydration rate, an increase in gel strength and TPAparameters compared with separate addition.3. Comprehensive utilization of wastes of tilapia was investigated. First, headsand viscera of tilapia were made into seasoning by protease hydrolysis. Theconditions of processing were determined through single factor and orthogonalexperiment. The indexes explored included the content of amino acid nitrogen, degreeof hydrolysis of protein, loss rate of amino acid and organoleptic evaluation indicators.The optimal reaction conditions of compound protease hydrolysis and maillardreaction: the ratio of trypsin and flavor protease) was1:1, reaction temperature was65℃,and reaction time was4h at pH8.5; the density of glucose was0.3mol/L, thedensity of L-cysteine was0.12mol/L, reaction temperature was120℃,pH was7.5and reaction time was80min. In the end, the product had deep fish fragrance, nofishlike smell. The rate of amino acid nitrogen lost is5.63%. Second, fishbones oftilapia was made into crispy fishbone products. The conditions of process weredetermined through single factor and orthogonal experiment. The indexes exploredincluded the fishbone hardness and sensory parameters. High pressure processingwith acids reduced the hardness of tilapia fishbones. The optimal condition wastemperature110℃, density of vinegar10%（v/v）, proportion of material and liquid1:20, and time25min. After optimized the conditions of process, fishbone hardnesswas17.0kg/cm when the optimal conditions were absorbed. The products dried at70℃for2-3h or fried at170℃for2-3min was crisp, golden, deeply fragrant andobtained better taste. Seasoning covered the bad smells to some extent and improvedflavour of products. The results from orthogonal experiment showed that the optimalconcentration of condiment was sugar15%, pepper6%and salt10%.