Study on the permeability of salt and quality change of tuna by the brine solution immersion freezing

In order to study the effects on tastes and quality of tuna by salt water frozen to the freezing point in the fishing vessels, the tuna was frozen by CaCl2, NaCl brine solution immersion and air freezing (the controlled) . The freezing curve from 5 to-18℃ by CaCl2, NaCl solution immersion and air freezing were drawn.The changes of permeability of salt, freshness indexes (sensory evaluation, total number of bacterial colony, WHC, TBA, TVB-N, met-myoglobin, histamine) of tuna under the brine solution immersion freezing process with impregnating time were tested after the tuna reached-18℃ (0h) . The results showed that freezing time of CaCl2 brine solution immersion freezing was 28 min which was faster than that of NaCl brine solution immersion freezing. The salt permeability in NaCl brine solution into tuna was from 4.88% to 9.66% within 0²0h, which was faster than that in CaCl2 brine solution. The sensory values of NaCl and CaCl2 group were lower than that of the air group after 12 h and 8h respectively. The changes of TBA, TVB-N and met-myoglobin of CaCl2 group were 0.330mg/100g, 1.175mg/100g and 3.58% respectively within 0²0h. The total number of bacterial colony, WHC and histamine were 3.389 lg CFU/g, 49.88% and 7.334mg/kg of CaCl2 group at 20 h respectively.Therefore, the quality and taste of fish would decline in salt water because of the dipping process. CaCl2 brine solution immersion freezing could not only improve freezing rate, but also reduce the amount of salt permeability, and the impact on fish taste in the freezing process. The results were a reference to optimize brine solution immersion freezing technology.