| Silver carp is one of the main freshwater fish species of China. Due to the limitation of consumption custom on fresh water fish in the international and the domestic markets, and the effects of factors such as processing and flavor characteristics of the fish itself, it has a low market price and needs to be further developed and utilized.This paper is mainly about the analysis and preparation of complex lipids from silver carp, and the study on their emulsifying properties and antioxidant activities.Firstly, distributions and compositions of the lipids different parts of silver carp and their fatty acid compositions were studied. The lipids distribution and composition were analyzed and compared by using Bligh-Dyer method, silica-gel column chromatography and thin layer chromatography(TLC). Results showed that complex lipids from the fish head was most abundant, about 2.2%. In complex lipids, the contents of glycolipids were close to those of phospholipids. Phospholipids from different parts were all composed of phosphatidylcholine(PC), phosphatidylethanolamine(PE), phosphatidyelserine(PS) and an unknown component which was later presumed to be phosphatidylinoitide(PI). Contents of PE and PC were significantly higher than those of other phospholipids components. Fatty acid composition of lipids from different parts of silver carp were analyzed by gas chromatography-mass spectrometry, results showed that the most abundant fatty acids from silver carp were palmitic acid and oleic acid. Compared with other freshwater fish, the contents of functional fatty acids such as docosahexenoic acid(DHA), eicosapentaenoic acid(EPA), and arachidonic acid(ARA) in silver carp were higher. The fatty acid compositions of total lipids, glycolipids and neutral lipids were similar. The contents of DHA and EPA in phospholipids were highest.Then, the extracting process of complex lipids from silver carp head was studied. Through the orthogonal experiment, the optimal conditions of extracting complex lipids from freeze dried silver carp head powder by ethanol were determined as follows: ethanol concentration 70%, ratio of solid to liquid 1:18, extraction temperature 37℃, extraction time 6h. Under the process conditions, complex lipid yield is 6.97%. Results also reflected the ethanol concentration had a certain influence on kinds of lipids, and should neither be too high nor too low. The content of monounsaturated fatty acid(MUFA) from silver carp head complex lipids was higher than that of phospholipids from silver carp head. The complex lipids from silver head had certain contents of DHA, EPA and ARA and total polyunsaturated fatty acid(PUFA), but were lower than phospholipids from silver carp head.Finally, emulsion properties and antioxidant activity of silver carp head complex lipids were studied, and compared with silver carp head phospholipids and soybean phospholipids. Results in vitro antioxidant activity of lipids showed that, in the experimental concentration range, the OH· eliminating ability of silver carp head complex lipids was weaker than those of silver carp head phospholipids and soybean phospholipids. But the reducing power of complex lipids was stronger than soybean phospholipids and weaker than silver carp head phospholipids. Complex lipids and phospholipids from silver carp head both had certain anti-oxidation capacity. The effects of emulsifier concentration, p H value, ionic strength and temperature on emulsion stabilization were researched. In the experimental concentration range, phospholipids from silver carp head achieved better emulsifying effect at low concentration, and the salt tolerance of complex lipids from silver carp head was weaker than soybean phospholipids. In neutral or alkaline conditions phospholipids from silver carp head had better emulsifying effect, in low temperature, emulsifying stabilities of 3 species of lipids were all good. |
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