Effect of different concentration CaCl_2 secondary refrigerant on salt permeability and quality of frozen tuna

The quality of salt- freezing tuna is affected by temperature and concentration of salt solution,and it is important to maintain the quality by increasing the freezing speed and reduce the salt permeability.The aim of this study was to evaluate the influence of salt concentration on salt permeability,sensory analysis and physicochemical indexes( drip loss,texture,TBA and met- myoglobin etc). The fresh tuna bulks were soaked in Ca Cl2 solution with temperature of-25,- 30,- 35 and- 40℃ and the samples frozen in air at- 25℃ was set as the control.Quality indices of frozen tuna bulks were determined after the central temperature of fish bulks reached-18℃. The results showed that the freezing time of tuna which soaked in-40℃ salt water were 5680 s shorter than that soaked in-25℃ solution.The quality characteristics of tuna frozen in-40℃ solution were better than those by other three freezing treatments(-25,-30,-35℃),whose sensory value,chewiness and TBA value were 9.48,237.48 and 0.58 mg /100 g,respectively.Furthermore,compared with lower concentration of Ca Cl2 solution with longer freezing time,a higher concentration of Ca Cl2 solution increased the freezing rate of tuna with lower the salt permeability.The lower temperature of salt solution had a better effect on maintaining the taste and quality of frozen tuna.