Optimization of technological conditions for microwave puffing ready-to-eat Thunnus alalunga skin

In order to investigate the optimal process of puffed ready-to-eat tuna skin,the influence of initial water content,water equilibrium time and microwave puffing time on the expansion degree of tuna skin was analyzed. Response surface method(RSM)was applied to optimize the process of microwave puffing tuna skin. Then the effect of different embrittlement conditions,such as blanching time,cooling time and mass concentration of muriate potash,on the crispness of tuna skin was investigated by orthogonal experiment. The tissue structure of tuna skin was characterized by scanning electron microscope(SEM). The results showed that the optimal puffing conditions were initial water content of 21.8%,water equilibrium time for 9.1 h,microwave power for 700 W,microwave time for 4 min. The expansion ratio of tuna fish was(1.24±0.03)under these conditions. Meanwhile,the optimal embrittlement conditions were blanching time for 2 min,cooling time for 2 min and mass concentration of muriate potash for 5.0 g/L. The brittleness of microwave puffing tuna fish could be reached at(41.17±0.28) N and the expansion ratio of tuna fish was(1.25±0.02).The analysis of physicochemical and SEM showed that the expansion ratio and crispiness of fish skin were remarkably improved,the obvious enlargement of fibrous tissue and the increase of slight fracture in fish skin were also observed after embrittlement. Thus it can be seen,the process of puffing and embrittlement for tuna skin was developed for obtaining high quality and good taste ready-to-eat tuna skin