| Pacific saury(Cololabis saira) is one of the most important marine commercial fishes in the world. They are mainly between 24 and 32 cm in knob length, and they can reach a maximum size of 40 cm. They have a short life-span of 1–2 years, but they will lay eggs almost all year after maturity. These characters decides that the large amount and strong capacity of resource recovery of Pacific saury. Japan is one of the main countries which catches Pacific saury and the total annual catch is about 300,000 t. Taiwan started to catch Pacific saury since 2001 in the North Pacific Ocean and got the good profit. According to the newest report, the catch from Taiwan was more than 160,000 t after Japan. The mainland started to catch Pacific saury since 2003 in North Pacific Ocean, though the catch was only 46,000 t, our country has good fishing skills, rich labour resource and large market. Also the catch and the need keep increasing. In the meantime, the price of Pacific Saury is low, so there will be a favorable prospect in our country. With the increasing processing volum, it will produce large wastes like viscera(10.50%). If these wastes can not be used properly, it will be a wasting of resoures or even environment pollution. The content of oil and lecithin from Pacific saury viscera can reach 21% and 8.85%, respectively. And as a marine fish, it is rich in unsaturated fatty acids, so Pacific saury can be a good resource of oil and lecithin extraction.We did some researches about the nutritional components and the usage of its processing wastes. To analyse the nutritional components and evaluate their nutritional value of Pacific saury in Northwest Pacific Ocean, the contents of moisture, ash, crude protein, crude fat, amino acids and fatty acid composition, as well as mineral elements in Pacific saury muscle were determined based on the current national standard methods. We got that the contents of moisture, ash, crude protein and crude fat were(60.62±0.48)%,(0.75±0.01)%,(17.63±0.34)% and(21.04±0.60)% respectively. The content of total amino acids was 18.67g/100 g wet weight, among which 8 kinds of essential amino acids accounted for 38%, the ratio of essential amino acids to non-essential amino acid was 0.79, the total amino acids score was 2786.44mg/g N. Trp and Met+Cys were the first and second limiting amino acids and the essential amino acids index(EAAI) was 83.65. Essential amino acids and flavor amino acid are rich which meet the FAO/WHO recommended amino acid pattern of high quality protein. 21 kinds of fatty acids in the crude fat were detected, among which the contents of eicosapentaenoic acid(EPA) and docosahexaenoic acid(DHA) were 5.17% and 11.27%, respectively. The ratio of n-3 to n-6 is also high. There were abundant of Na, Mg, P, Fe and other essential minerals in Pacific saury muscle. We can conclude that the contents of crude protein and fat were high. The ratio of essential amino acids was fit for human health, and rich in EPA and DHA. Therefore, Pacific saury has high nutritional value.Because of large content of oil and lecithin in Pacific saury, oil and lecithin were respectively extracted from Pacific saury viscera by supercritical carbon dioxide(SC-CO2) and combined with the cosolvent of anhydrous ethanol, using organic solvent(ethanol and acetone) extraction to extract lecithin as comparison. The optimum extraction conditions of the oil and lecithin from Pacific saury viscera by SC-CO2 were studied in the paper. Using wet Pacific saury viscera as the experimental material, the extraction parameters of extraction temperature, extraction pressure and extraction time were optimized based on single-factor and response surface methodology. The optimum extracting conditions were obtained as follows:extraction pressure 45 MPa, extraction temperature 55°C and extraction time 3h. Acconding to the response surface model: Y=20.14+ 2.21A-0.086B+1.07C+0.09AB+0.79AC+0.43BC-1.52A2-3.55B2-1.07C2. The predicted yield of oil from Pacific saury viscera under these conditions could reach 21.7g/100g(wet) and the actual yield of oil is 22.07±0.33 g/100g(wet). There was no lethin detectable in oil. Using deoiled Pacific saury viscera as experimental material and ethanol as co-solvent for second extraction of lecithin, the optimum extraction conditions were obtained as follow: extraction pressure, extraction temperature, flow rate and extraction time were 45 MPa, 50°C, 2.0ml/min and 2.5h, respectively. Acconding to the response surface model: Y=7.88+0.68A+0.45B+0.73C+1.11D-0.38 AB +0.20AD-0.25CD-0.20A2-0.87B2-0.25C2-0.70D2. The predicted yield of lecithin from Pacific saury viscera under these conditions was 9.2g/100g(wet) and the actual yield of lecithin is 9.23 g±0.12g/100g(wet).Thin layer chromatography was performed to separate the individual phospholipids. The major phospholipids of Pacific saury lecithin were quantitatively analyzed by high-performance liquid chromatography(HPLC). Phosphatidylcholine(PC)(63.87%±1.67%) and phosphatidylethanolamine(PE)(32.30%±1.72%) were the main phospholipids of the lecithin. The fatty acids profiles of oil, lecithin, PC and PE were analyzed by Gas Chromatography-Mass Spectrometer(GC-MS). For oil, palmitic acid was the major saturated fatty acid(SFA). The amount of this acid was(9.47±0.38)%. Erucic acid was identified as the major monounsaturated fatty acid(MUFA) in oil, accounted for(20.62±0.27)%. In the n-6 PUFA fraction, arachidonic acid(ARA) was the major n-6 PUFA with the level of 2.36% in oil. Linolenic acid and Homogamma linolenic were found to be at low amounts in the PUFA fractions. EPA was found to be at the highest level in the n-3 PUFA fraction in oil with a value of 13.82%. DHA was the fatty acid at the second high amount in n-3 PUFA of oil. The n-3/n-6 of Pacific saury viscera oil reached 5.03. Our study has revealed that oil from Pacific saury has a high nutritional value for human consumption due to its high n-3/ n-6 ratio. For lecithin, among total fatty acids, PUFAs were present in higher amounts, especially DHA(27.44%) in the lecithin. For PC and PE, the content of SFA was the highest among total fatty acids. And the contents of PUFA accounted for 34.49% and 32.99%, respectively. The important PUFAs were EPA(6.51%, 6.41% of total fatty acids) and DHA(21.99%, 22.08% of total fatty acids), which were found in significantly large amounts in all lipid fractions. Besides, we also studied the oxidation stability of lecithin, and lecithin showed high oxidative stability over a certain period. EPA and DHA were the major parts of unsaturated fatty acids which were the most susceptible to oxidation in lecithin. |
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