Effects Of Ozone Water Treatment On Protein Oxidation And Lipid Oxidation And Quality Of Tilapia Fillets

The effects of ozone water treatment on both proteins and lipids oxidation and the quality of tilapia fillets are studied in this thesis,with the treatment conditions of 2.5mg/L 10 min,5mg/L 10 min, by storing the processed tilapia fillets at 1 × 1 ℃ for 15 days,and there is no any treatment in the control group. The contents and results are as follows:1. Effects of ozone water treatment on protein oxidation of tilapia fillets: after accepting ozone water treatment, the content of myofibrillar protein carbonyl and hydrophobicity of tilapia fillets increase constantly; the content ofactomyosin total sulfhydryl decreases constantly while the content of disulfide bond increases constantly; the myoglobin content decreases constantly while the relative content of metmyoglobin increases constantly. In the control group 2.5mg/L 10 min and 5mg/L 10 min, the content of carbonyl increases to 66.93、 88.64、98.23nmol/mg respectively. The hydrophobicity increases to 173.18、 175.51、177.55/μg respectively. The content of total sulfhydryl decreases 30.38%、41.93%、42.55% respectively. The disulfide bond increases 12.37%、 16.19%、20.36% respectively. The water holding capacity(WHC) decreases 11.03%、18.05%、32.71% respectively.The content of myoglobin decreases 0.79、0.82、0.71mg/g respectively while the content of metmyoglobin increases 53.08%、61.35%、81.95% respectively. What’s more, L * value of tilapia fillets increases at first and then decreases, both a * and b * values show a downward trend. The results show that ozone water treatment can promote myofibrillar protein oxidation, but has little effect on the hydrophobicity. It also can help to translate sulfhydryl into disulfide bond and change actomyosin molecular structure as well as the content and existence form of myoglobin,thereby affecting color of fish. What is more, the group 5mg/L has greater effects than group 2.5mg/L on protein oxidation.2. The effects of ozone water treatment on lipid oxidation of tilapia fillet: After accepting different ozone water treatments from groups, the acid value, POV value and TB A value of tilapia fillets during the period of storage show an upward trend. However, the acid value is lower than that in control group,while the POV and TBA values are higher compared with control group. It shows that ozone water can inhibit fat hydrolysis and promote lipid oxidation of tilapia fish. And the group 5mg/L has greater effects than 2.5mg/L group on fat oxidation. Because of the instability of peroxide and the stable content of MDA as well as the irregular change of peroxide value, therefore TBA value is more suitable to be as the indicator of measuring the fish fat oxidation. There is a a good correlation between protein oxidation and lipid oxidation in tilapia fish that has accepted the ozone water treatment.That is,the correlation coefficient between TBA value and the relative contents of carbonyl, total sulfhydryl content and metmyoglobin is 0.986,0.920 and 0.947 respectively.3. Make the TVB-N value as the indicator to determine the shelf life. The shelf lives of tilapia fillet in control group, group 2.5mg/L and group 5mg/L are 7.5、10.4、11.6 days respectively. With the prolong of the storage,the PH value of tilapia fish in control group, group 2.5mg/L and group 5mg/L increases from 6.11、6.20、6.17 to 7.10、6.82、6.75 respectively,which shows that ozone water treatment can slow the freshness decline of tilapia fillets.Compared with the control group, the hardness of tilapia fish in ozone water treatment group shows a downward trend; and there is no obvious change in elasticity. So the ozone water treatment can slow the decline in elasticity. The sensory evaluation score shows that the color, smell, organization and elasticity of tilapia fillets in the control group and ozone water treatment group change significantly. And there is no significant difference in sensory evaluation scores of group 2.5mg/L and group 5mg/L with same storage time (P>0.05). Correlation analysis and Loading analysis are carried out on sensor to optimize the new array of electronic nose sensor,namely, the new sensor array consists of W1C, W5S, W1S, W1W, W2S, W2W and W3S.The principal component analysis of optimized sensor array shows that the electronic nose can distinguish tilapia fillets into deteriorated meat and normal meat during storage so that the quality transition time of tilapia fillet is consistent with the shelf life.Based on the the effects of ozone water treatment on protein and lipid and quality, we make a comprehensive assessment of treatment conditions,that is,the treatment condition of 2.5mg/L 10min is better than 5mg/L 10min.