| The meat of Tilapia is delicious and eutrophy, it has been thought of one of the main sources of protein in the future. Tilapia has been processed many kinds of products, coconut breaded tilapia fillets is a typical kind among them,and it is popular and good evaluated with consumers,so it has a good prospect in the market. The tilapia fillets were utilized as raw materal in this study, and this thesis research focus on these key technologies of coconut breaded tilapia fillets during produce,process and storage:ozone floating wash treatment, non-phosphorous water-retention agent development,optimizing the formula of breaded film,fried technology and changes of quality during storage. These technologies aim to ioprove the safety and quality of coconut breaded tilapia fillets.The results are shown below:1. Study of ozone floating wash treatment. The percent reduction of bacteria was selected as response value and response surface methodology (RSM) was applied to optimize the optimal treatment conditions of ozone floating wash to tilapia fillets. There are three critical parameters which effect the ozone percent reduction of bacteria:flow rate, treatment time and pH in solution. The optimal treatment conditions were as follows:ozone flow rate 12.5mg/min, treatment time 9 min and pH 5.5. Under this optinal condition:the percent reduction of bacteria was 87.4% and the texture of tilapia fillets had been improved.2. Technology of water-holding. Studying the water-holding capacity of glutamine transaminaase, xanthan gum, sodium lactate, sodium citrate and sodium bicarbonate on frozen tilapia fillets based on the indexes of the yield of weight increasing after being soaked and drip loss in order to select the proper non-phosphorous water-retention agents and their range of concentration. The results of optimization by orthogonal array design indicated that tilapia fillets treated by the compound non-phosphorous water-retention agent composed with0.6% glutamine transaminaase,0.6% sodium lactate,2.5% sodium citrate and 2.0%sodium bicarbonate are more similar to untreated fillets on texture and lower on cooking loss and centrifugal compared with compound phosphates. So the compound non-phosphorous water-retention agent can developped the water-holding capacity and may an alternative to compound phosphates.3. Optimizing the formula of breaded film. Adding proper starch (com starch, cassava starch), food hydrocolloids (xanthan gum, guar gum) and isolated soybean protein can increase the percent of pick-up of breaded, moisture content, and fragility and decrease oil absorption.The optimum added content is the ratio between cassava starch and wheatmeal is 1:2,0.5% xanthan gum and 10% isolated soybean protein.On this condition, the coconut breaded tilapia fillets obtain best quality.4.Fried technology.In this study, coconut breaded tilapia fillets were fried in soybean oil and moisture loss, oil absorption, fragility, color and sensory attributes were used to evaluated the quality of samples. Coconut breaded tilapia fillets were fried at 170℃ for 1.5,2.5,3.5 and 4.5min or fired at 160,170,180 and 200℃ for 2.5min. LF-NMR was used to study the relationship between moisture loss and oil absorption in the process of frying. Results showed that longer frying time and higher frying temperature lead to higher moisture loss and higher oil absorption, which persenting a positive correlativity. In addition, coconut breaded tilapia fillets fried at 170℃ for 2.5min showed golden yellow color and higher texture property, maintaining the highest sensory score.5. Changes of quality. Studying the storage of quality mainly to explore changes of total viable count, moisture content, color and sensory evaluation of coconut breaded tilapia fillets at the tempurature of-18℃,-7℃ and 4℃. Results showed that: comparing with samples keeped at-7℃ and 4℃, coconut breaded tilapia fillets keeped at-18℃ maintained the best quality. |
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