Preparation Of Phospholipids From Three Kinds Of Freshwater Fish And Shrimp And Comparison Of Their Functional Characteristics

This paper is based on a systematic analysis of lipids in various parts of the three freshwater fish and shrimp which include grass carp,silver carp and crayfish,the phospholipids of the three freshwater fish and shrimp were extracted by using ethanol extraction from their processing byproducts,and studied on their emulsifying properties and antioxidant properties compared with the common commercial soybean lecithin.Firstly,the total lipids of different parts from the three freshwater fish and shrimp were extracted by using Bligh-Dyer method,the content of neutral lipids,glycolipids and phospholipids in the total lipids of different parts were analyzed and compared by using silica gel column chromatography,the distribution,compositions and contents of phospholipids of different parts were analyzed and compared by using thin layer chromatography?TLC?,the fatty acid compositions of the phospholipids in different parts of crayfish were also tested by using gas chromatography-mass spectrometry?GC-MS?and compared with total lipids,neutral lipids and glycolipids.It was shown that the content of total lipids of grass carp visceral was the most abundant,the content of phospholipids in grass carp back was the highest.The total lipids in the viscera and head of silver carp were the most abundant,the content of phospholipids in silver carp back was the most abundant,it is the same with grass carp,but the total content of phospholipids was lower than those of all parts of grass carp.The total lipids of crayfish cephalothorax were mainly neutral lipids but still contained a certain amount of phospholipids?16%?,the contents of total lipids of crayfish in clamp,tail shell and tail meat were lower than in cephalothorax,but the contents of phospholipid in different parts of crayfish were up to 60%.,phospholipids in different parts of three freshwater fish and shrimp mainly contained phosphatidylcholine?PC?,phosphatidylethanilamine?PE?,and sphingomyelin?SM?.Fatty acids of the phospholipids in in all three types of freshwater fish and shrimp are mainly polyunsaturated Fatty Acids?PUFAs?,including docosahexaenoic acid?DHA?,eicosapentaenoic acid?EPA?and arachidonic acid?ARA?of the three freshwater fish and shrimp' total lipids were tended to bind to phospholipid molecules.Secondly,with the index of the extraction purity and extraction rate of phospholipids,we used ethanol method to extract phospholipids from the by-products of three freshwater fish and shrimp.The optimal conditions of extracting phospholipids from freeze dried grass carp head powder by ethanol were determined as follows: ethanol concentration 80%,ratio of solid to liquid 1:8,extraction temperature 55°C,and extraction time 4.5h,under the conditions,the purity of phospholipids was 83.24%,and the extraction rate of the phospholipid products was 3.03%.The optimal conditions of extracting phospholipids from freeze dried silver carp head powder by ethanol were determined as follows: ethanol concentration 80%,ratio of solid to liquid 1:10,extraction temperature 35 °C,extraction time 3h,under the conditions,the purity of phospholipids was 74.45%,and the extraction rate of the phospholipid products was 3.35%.The optimal conditions of extracting phospholipids from freeze dried crayfish cephalothorax powder by ethanol were determined as follows: ethanol concentration 90%,ratio of solid to liquid 1:4,extraction temperature 45°C,extraction time 3h,Under the condition,the purity of phospholipids was 69.46%,and the extraction rate of the phospholipid products was 5.17%.Finally,the emulsification properties and antioxidant properties of phospholipids from three freshwater fish and shrimp were studied.The emulsification ratio of different kinds of phospholipids increased gradually with the increase of phospholipid concentration in the non-ionic environment at room temperature,and the increase of phospholipids from the three freshwater fish and shrimp were slower than that of soybean lecithin.With the increase of ionic strength,the emulsifying capacity of different kinds of phospholipids gradually decreased,and the effects of CaCl₂ on emulsifying capacity of different kinds of phospholipids were greater than that of Na Cl.The emulsifying capacity of phospholipids from three kinds of freshwater fish and shrimp were better under p H=7 and low temperature conditions.The emulsifying capacity of phospholipids from three freshwater fish and shrimp were better under neutral and low temperature conditions,but with the increase of p H and temperature,the emulsifying capacity of the phospholipids from grass fish head,silver carp head and soybean lecithin decreased.The emulsifying capcity of crayfish cephalothorax phospholipid was not affected,in general,the emulsifying stability of crayfish cephalothorax phospholipid was better than that in grass carp head,silver carp head and soybean lecithin.In the range of test concentration,the ·OH eliminating ability and reducing power of silver carp head phospholipids were better than those of the other three kinds of phospholipids;the phospholipids from the three freshwater fish and shrimp had certain antioxidant activity which would improve with the increase of the added concentration.When the phospholipid concentration was 0.05%,the antioxidant activity of the phospholipids from the three freshwater fish and shrimp were slightly lower than that of soybean lecithin.When the added concentration was 0.1%,the antioxidant activity of silver carp head phospholipids was higher than that of soybean lecithin.When the added concentration was over 0.2%,the antioxidant activity of the phospholipids from the three freshwater fish and shrimp were higher than that of soybean lecithin.Overall,when the added concentration of phospholipids was over 0.1%,the antioxidant activity of silver carp head phospholipids was significantly higher than that of the other 3 phospholipids.