Research On Key Technology Of Skipjack High-value Process

Tuna, the so-called “submarine gold”, is delicious, nutritious and has a high level of activesubstances. Skipjack is a kind of tuna species with great commerce value, as well as the mostimportant one of the fishery targets in the midwestern Pacific. At the same time, it is a low-valuetuna which is aboundant of dark muscle and has a bad taste. However, it still has a great marketpotential because of the large catches and cheap price. Same as the other tuna species, a lot ofwastes will be produced during the skipjack processing, such as fish head, viscera, minced meat,bones, dark muscle, skin, etc., accounting for50%-70%of the total weight. In order to utilize theseresources resonably, improve the added value, and realize the high value processing, this topic hasselected the skipjack and its wastes as raw materials for the research.Firstly, the nutrient composition of skipjack was determined，showing that skipjack belongs tothe type of high protein, low fat fish. It was rich in amino acid contents, and8essential amino acidsand2semi-essential amino acids (histidine and arginine) were detected in skipjack. Activesubstance, such as DHA、EPA were also founded.Secondly, the effects of processing temperature on the volatile compounds in tunas werestudied using an electronic nose (E-nose) and gas chromatography mass spectrometry (GC-MS)combined with headspace solid phase microextraction (HS-SPME). The characteristic flavor andvolatiles of fresh skipjack and95℃,150℃heated skipjack were founded.Thirdly, in order to improve the quality of skipjack muscle, response surface meehodologywere designed to optimize the process. The optimal process parameters were as follows:0.64%transglutaminase,0.20%sodium tripolyphosphate,1.85h soaktime. The gel network structure oftuna muscle after being treated was found to be much denser, using scanning electron microscopy.Fourth, processing technology of instant skipjack was studied, the recipe was optimized usingsingle orthogonal test. The quality changes in the storage were determined as well. The shelf-life ofthe product under18-20℃was predicted by ASLT method.Fifth, the process technique of skipjack noodle using twin-screws extrusion was optimized.The effects of fish content, barrel temperature, moisture content on the noodle quality were studied. The optimal process parameters (15%fish contents,100℃barrel temperature,16%moisturecontents) were founded using single factor experiment and orthogonal test. On condition of that,skipkack noodle tastes best.Sixth, based on traditional technique of canned skipjack, the contents of fish, soup, ingredientswere optimized using orthogonal test. Three recipes of skipjack were obtained, including fruit andvegetable canned tuna (five-flavor), peas canned tuna (fragrant and spicy), canned tuna offlammulina velutipes (sweet and spicy).Seventh，the preparation technology of CMC active calcium by mixed acids of citric acid andmalic acid applied to skipjack bone was studied by orthogonal test.The effects of mixing ratio, totalacid amount, soaking time and temperature were examined. The optimum condition was as follows:mixing ratio3:2, total acid amount10g/100mL, soaking time2h and soaking temperature60℃。The product of active calcium was parepared by drying the calcium extract.