Influnce of microwave heating combined with vacuum cold water immersion on sea cucumber (Stichopus japonicus) soaking effects

In order to investigate a novel microwave heating combined with vacuum cold water immersing technique of dried sea cucumber (Stichopus japonicus).The effects of microwave heating time(25~50 min) and temperature(50~90 ℃) on the soaking effect of sea cucumber were studied with swelling ratio, nutrient loss and sensory quality, which were optimized by orthogonal experiment. Under the optimum microwave heating conditions, the effect of vacuum and atmospheric pressure on the soaking of sea cucumber were studied. The effects of microwave heating combined with vacuum soaking treatment on the quality of sea cucumber were compared with those of boiling water-atmosphere soaking. The results showed that microwave heating temperature and time had significant influence on the swelling (P<0.01). An increasing tendency was observed on the swelling ratio of sea cucumber, followed by a decrease with the increase of heating temperature. In the range from 50 ℃ to 80 ℃, with the increase of heating time, an increasing tendency of the swelling ratio was showed, followed by a decrease while over 90 ℃. The optimum heating parameters of sea cucumber were determined by orthogonal experiment as heating at 70 ℃ for 40 minutes. Under the optimized conditions, compared with the sea cucumber under treatment of boiling water-atmosphere soaking, the sea cucumber treated by microwave heating combined with vacuum in cold water was swelling completely on the first day, reached the maximum value of 13.03 time and the maximum sensory score of 13.46, and the total loss rate of soluble protein and polysaccharide decreased by 53.85% and 25.41%, respectively. And it exhibited even better texture characteristics than those under boiling water and atmospheric pressure (P<0.05). FTIR (Fourier Transform Infrared Spectroscopy) showed that the process was milder under microwave heating aided vacuum technique, which was conducive to maintaining integrity of the secondary structure of protein and functional characteristics during soaking. The results provide a theoretical and technical support for the development and application of new technology on sea cucumber.