| The best methyl-esterification method of fatty acid in Coilia ectenes meat was selected and optimization in this study. The nutritional composition(proximate composition, fatty acids, amino acids and minerals) in meat of Yangtze River-coilia,Yellow River-coilia and East Sea-coilia were investigated in this study. Meanwhile,the nutritional composition in meat of Yangtze River-coilia at different stages(from stage Ⅱ to stage Ⅴ) and Yangtze River-coilia after spawning were also investigated in this study.1. Among the most commonly used methods of methyl-esterification(KOH-methanol, sulfuric acid-methanol and boron trifluoride-methanol method), the best method was selected according to the chromatogram, depending on the number of peaks and areas of peaks. Among them, BF3-methanol was chosen for the following determination. According to single factor experiment of BF3-methanol, the best condition for BF3-methanol was: volume of KOH-methanol is 3 ml, volume of BF3-methanol is 3 ml, reaction time is 7 min and reaction temperature is 90 ℃.Result shows that this method had the advantage of short-timing and better efficiency. The method has good reproducibility and repeatability, with the RSD of reproducibility experiment is less than 3% and the recoveries is between 93.69% ~ 106.35%.2. From the determination of nutritional composition in meat of Yangtze River-coilia, Yellow River-coilia and East Sea-coilia, all three kinds of Coilia ectenes were characterized as high protein contents and high fat contents. The crude protein content is 14.03% ~ 16.37% and crude fat content is 10.30% ~ 10.30%.Monounsaturated fatty acid(MUFA) is most abundant in Coilia ectenes meat(25960.35 mg/100 g, 18879.39 mg/100 g and 30880.24 mg/100 g in Yangtze River-coilia, Yellow River-coilia and East Sea-coilia, respectively), they accouted for more than 50% of total fatty acid content. Among MUFA, C18:1n9(oleic acid) is themost abundant one. The contents of C18:1n9 in three kinkds of Coilia ectenes is nearly half of MUFA contents, as the main fatty acids in Coilia ectenes. East Sea-coilia has a lifetime live in the sea. So, when compared it to the Yangtze River-coilia and Yellow River-coilia, East Sea-coilia contains more abundant polyunsaturated fatty acids(PUFA), especially DHA. Yangtze River-coilia, Yellow River-coilia and East Sea-coilia are rich in amino acids, which content(dry weight) is43.59 g/100 g, 53.21 g/100 g and 37.34 g/100 g for Yangtze River-coilia, Yellow River-coilia and East Sea-coilia, respectively. Glu in the most abundant amino acid in three kinds of Coilia ectenes. while Trp is the lowest. However, amino acids composition in three kinds of Coilia ectenes were coincidence with recommendation of FAO/WHO, the total essential amino acids content(TEAA) and total amino acid content(TAA) ratio is 38.70% ~ 38.70%, total essential amino acids content and total non-essential amino acids content(TNEAA) ratio is 62.77% ~ 65.66%. And the AAS of theses three were all above 100. Indicated that these threes kinds of Coilia ectenes could provide relatively high quality protein. The significant differences in protein content of three kinds of Coilia ectenes results in the significant differences in amino acids contents. But the three has a similar amino acids composition, however. K, Na,Ca were the most abundant minerals in three kinds of Coilia ectenes, while Zn and Fe is the most abundant micro-elements.Coilia ectenes has the characteristic of rich in Ca content(612.28 mg/100 g, 426.09 mg/100 g and 385 mg/100 g in Yangtze River-coilia,Yellow River-coilia and East Sea-coilia, respectively).3. Nutritional composition in meat of Yangtze River-coilia at different reproductive stages(stage Ⅱ, stage Ⅲ, stage Ⅳ and stage Ⅴ) and Yangtze River-coilia after spawning were determined. The results showed that, in the process of gonad development, the moisture content and crude protein content increased significantly(moisture content is 67.07% ~ 67.07% and protein content is 14.50% ~16.38%). On the contrary, crude fat content(5.19% ~ 15.38%) was significantly declined, while ash content(0.90% ~ 1.09%) has a decline, after the increase from stage Ⅱ to stage Ⅳ. Illustrated that the fat is the main energy source in the process of gonad development. Among them, MUFA predominated the fatty acids. In the earlystage(stage Ⅱ to stage Ⅲ) of gonad development, Yangtze River-coilia consumed a large amount of n-3 fatty acids in the PUFA, which mainly consist of EPA and DHA. C20:3n6 and C20:4n6(ARA) is a precursor of the synthetic arachidic acid.They will fish accumulated in fish body before transferred to the ovary. Amino acidscontents were significantly increased during the gonad development, but amino acid composition is relatively stable, and comparable to recommendation of FAO/WHO(TEAA/TAA is 39.18-40.93%, TEAA/TNEAA 59.07-64.44%). Meanwhile, AAS were all greater higher than 100, indicated that meat of Yangtze River-coilia at all reproductive stages could serve as a good source of amino acids. Cu and Mn as elements relative to spawning, the contents was significantly decreased at stage Ⅴ. |
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