| The tilapia industry has been one of the important pillars of the fishery economy in Hainan province since 2000.But in recent years,due to the international aquatic product competition,the prohibition on the import tilapia fillets treated by CO in European Union and other countries,and the efforts by Latin America to improve the processing quality of tilapia,Chinese tilapia products was negatively affected in the international market,lending to a decline in economic interest.But.Based on the actual situation of Chinese tilapia processing enterprises,this article search aims of improving the product quality so that to enhance the international market competitiveness of Chinese frozen tilapia fillet products by optimizing technological parameters and establishing new methods for quality evaluation.After investigated some tilapia processing companies in Hainan,Guangdong,Guangxi,and Fujian provinces,discovering problems and participating in production practices,designed field tests and related research,we designed this study and optimization programs.The main results are as follows:(1)Test and improvement of the relay process of fish was proposed and came up with a new relay method.Firstly,selected a pH value regulator of the relay water,and then conducted the single factor test on the pH value,NaCl content(salinity),additive usage,fish-water ratio.Compared and analysised with the quality during storage,determined the ratio between fish and water,pH,and salinity as the main factors;subjected to orthogonal tests and combined with the actual production conditions,and the optimized conditions for conservation are determined as follows:ratio between fish and water 1:1,pH value 5.5,salinity 8 0‰.Verified by trial production,this condition can effectively suppress the deterioration of color quality a*value and conductivity,total volatile base nitrogen(TVB-N),and the preservation period of fillet raw materials can be extended.(2)Selection and compounding the send lubricious agent of tilapia fillets.According to the use standard of "GB2760-2014",potassium sorbate was selected as the main coloring agent by the single-factor test of color formers,and choosed potassium sorbate,fish-water ratio,treating time,and coloring method were also selected in single factor tests.The concentration of potassium sorbate,sodium erythorbate,and the treating time were determined by orthogonal test.The color of fillets was determined and the optimal coloring condition was potassium sorbate 0.075 g/kg,sodium erythorbate 0.2 g/kg,treating time 30 min.The color can be improved,L value,a*value was 48.2 and 9.3167,respectively.(3)Treating tilapia fillets by pre-cooling measures which used in fruits,vegetables and meat processing.Added pre-cooling process after the relay and section.Detected and analyzed the freshness indicators of fillets with pre-cooling and comparing them with no pre-colling fillets.The test results showed that pre-cooling can prolong the stiffening period of fish fillets,reduce the degree of body reduction,and improve the quality of fish fillets.(4)Improve the process of frozen fish fillets.Three groups of freezing temperature were selected within the fluctuation range of the freezing temperature in the actual production of the factory and the required freezing time corresponding to the requirement was determined.Testing the fish fillets prodected in different freezing processes in same storge environment.The results of comparative analysis of the groups showed that the freezing conditions had a significant effect on the fillet color,Aw,hardness,and TVB-N value.The lower the freezing temperature,the faster the corresponding freezing speed and the better quality that fish fillet get.After repeated field trials,the best freezing temperature of frozen tilapia fillets was-40±0.5?,and the speed of the double spiral chiller was 44,which corresponds to a freezing time of about 40 min.For fish fillets of different specifications,adjustments can be made on this basis.(5)Optimized and selected the partial freezing temperature.According to the definition of traditional partial freezing,the partial freezing temperature of tilapia fillets should be-4?.In this experiment,fish fillets were quickly frozen at-6?,-8?,and-10? as storage temperatures,and measured the a*values,pH values,texture characteristics,TVB-N were periodically measured,and regard TVB-N 30 mg/100g as the end point of quality.and its shelf-life was determined to be 39 d,43 d,and 56 d,respectively.At the same time,the shelf life prediction of the Arrhenius equation isk=1.90311×10E6·exp(39730/RT)(6)Detection of quality changes in frozen fish fillets produced by the company.The storage process of frozen tilapia fillets to be exported by the company is been continuous real-time monitored for five months in temperature and quality changes,and linked the physical property indicators of the products with TVB-N to observe the effect of temperature differece between the storage environment and the center of the fish fillet,trty to find a quickly method for determining the fillet quality.The result shows that the a*value and the conductivity have a closer correlation with TVB-N,and their corresponding fitting functions arey=-0.5936 x2+9.1345x-15.517(R2=0.9562)y=0.001x+0.3718(R2=0.96127)In the formula,the independent variables are the a*value and the conductivity value,the dependent variable is the corresponding TVB-N value.By measuring the independent variable and calculating the corresponding TVB-N value and compare with 30 mg/100g.Therefore,in the production,colorimeter or conductivity meter can be used to quickly determine and predict the freshness and quality of frozen fish fillets during the storage. |
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