Research On Keep Fresh Technology Of Tilapia Fillets By Partial Freezing Combined With Modified Atmosphere

Tilapia which has delicious meat, high protein content and rich nutrition is known as "the most valuable fish in the 21st century". Tilapia is an important economic fish in Guangdong, Hainan, Guangxi and Fujian and especially the frozen tilapia fillets are the main products exported to international markets. More and more consumers are fond of ice fresh tilapia in recent years. Because the higher requirements for the freshness and texture quality of tilapia, tilapia preservation technology has become a hot research at home and abroad. This study choosed the tilapia fillets as experimental materials and the pH, conductivity, sensory evaluation, texture and TVB-N were assessed. Combined atmosphere method with superchilling technology, the study proposed "on the base of improving and perfecting the superchilling technology to keep tilapia fillets fresh". This study was mainly focused on the following aspects:1?The effect of different lethal methods upon the superchilling preservationThe comparison of two lethal modes of live slaughter and cold water immersion was made by analysis of their effects on the tilapia fish quality, and the differences of freshness-keeping effect of fillets treated with the above two methods under the partial freezing condition were investigated. The result showed that ice water impregnating method was superior to live slaughter method in maintaining the freshness of tilapia fillets under the partially frozen condition, it can prolong the freshness of fillets about 2-4 days.2?The effects of different processing methods on fillet qualityIn order to explore the effects of different processing methods on fillet quality, in this experiment we using quick-frozen method and slow-frozen method. Comparing the preservation effects on tilapia fillets with the two kinds of the frozen processing method. The results showed that pH, conductivity and TVB-N were significantly different, but the water activity and texture parameters were not significantly different. The result shows that quick-frozen method can slow down the process of putrefaction of tilapia fillets.3?Study on superchilling technology of tilapia filletsThe preservation effects of tilapia fillets were compared under conditions of freezing-point storage(-2?), superchilling storage(-4?), frozen storage(-21?). The result showed that the fresh period of tilapia fillets in-2? was 16 days. The tilapia fillets in-21? had long fresh period, but it cannot keep good quality. The tilapia fillets in-4? is as long as 20 days with good quality.4?Study on gas proportionThis experiment studied the single factor experiment of the aerated proportion of CO2 and O2 to determine their best proportion. The result showed that in the single-factor experiment of CO2, when the proportion of CO2 is 50%, bacteriostatic effect is the best, but the tilapia fillets would be sour and brown. The result of the single-factor experiment of O2 showed that when the proportion of O2 is 40%, the tilapia fillets would keep their bright red color.5?Study on superchilling combined with modified atmosphere technology of tilapia filletsCombined with the results of the single factor test of the aerated proportion of CO2 and O2. The study on superchilling combined with modified atmosphere technology of tilapia fillets was conducted under the temperature of-4? to explore the best composition of CO2, O2 and N2?According to the above results, the best gas proportion was:50%CO2/ 40%O2/10%N2 under-4?. The shelf life can be up to 30 days.