南极磷虾(Euphausia superba)脂肪与蛋白含量的季节变化

Seasonal Variation in Lipids and Protein Content of Antarctic Krill(Euphausia superba)

为了有效提取营养功效和附加值均更高的磷虾油,对南极磷虾(Euphausia superba)资源的综合开发利用提供参考,利用2013年7-8月和2013年12月-2014年5月在南乔治亚群岛和南设得兰群岛附近海域采集的南极磷虾样品,采用索氏抽提法,分别用无水乙醇、丙酮、石油醚、正己烷、乙酸乙酯、环己烷6种常见的有机溶剂作为提取试剂,对南极磷虾体内的脂肪进行提取,并确定最佳萃取溶剂。同时对南极磷虾脂肪、蛋白含量的季节变化及其与体长的关系进行了分析。结果显示,无水乙醇为南极磷虾脂肪提取的最佳溶剂。南乔治亚群岛海域7-8月南极磷虾脂肪含量和蛋白含量(干重)分别为(22.03±0.51)%和(64.52±0.16)%;其中,全长小于40 mm的磷虾个体,脂肪与蛋白含量均显著高于全长大于40 mm的个体(P<0.05)。从南极的初夏到秋末,南设得兰群岛海域的南极磷虾脂肪含量呈逐渐上升趋势,由12月的(19.83±0.04)%上升至翌年4月的最大值(30.58±0.02)%;5月则略有降低,为(28.66±0.03)%。与此相反,南极磷虾的蛋白含量则是12月最高、4月最低,分别为(66.75±0.14)%和(58.02±0.23)%;脂肪含量与蛋白含量呈显著负相关(P=0.005)。研究结果对南极磷虾渔业及其生产安排具有直接的指导意义。

Antarctic krill （Euphausia superba） is a rich resource of polyunsaturated fatty acids and proteins. Therefore the contents of the two nutritional components are the determining factors of the economic value of Antarctic k.rill. To help improve the efficiency of utilization of Antarctic krill, we employed the Soxhlet extraction method and selected the optimal solvent for lipid extraction from anhydrous ethanol, acetone, petroleum ether, hexane, ethyl acetate and cyclohexane. We also analyzed the seasonal variation in the levels of lipids and proteins, and investigated the effect of the body length on the nutritional contents of Antarctic krill. Samples were collected from the water nearby the South Georgia Islands between June and August 2013 and from the water nearby the South Shetland Islands between December 2013 and May 2014. It shows that anhydrous ethanol was the best extraction solvent examined for determining the lipid content of Antarctic krill. The contents of lipids and proteins of samples from the South Georgia Islands were （22.03±0.51）% and （64.52±0.16）% （in dry matter） respectively. The levels of both lipids and proteins of smaller individuals （〈40 mm in total length） were higher than those of the larger ones （〉40 mm, P〈0.05）. The lipid content of samples from the South Shetland Islands showed an increasing trend from early summer to late fall, the level raised from （19.83~0.04）% in December to the peak value （30.58±0.02）% in April, followed by a decline to （28.66±0.03）% in May. In contrast, the protein content was the highest in December （66.75±0.14）% and the lowest in April （58.02±0.23）%. There was a significant and negative correlation between the lipid content and the protein content （P=0.005）. These results can be used directly to guide the arrangement of actual fishing operation of the krill fishery.