| Freshwater fish is a traditional aquaculture species in China,with a long history and a wide variety of species.Its common characteristics are high protein content,easy absorption,low fat content and mainly composed of unsaturated fatty acids.The market value of freshwater fish is low due to the restriction of freshwater fish consumption habits and the influence of its own factors,which needs further development and utilization.In this paper,we studied the fat content,fatty acid composition,phospholipid composition and content of freshwater fish,texture,gel strength,whiteness,water holding capacity,crude fat content,phospholipid composition and content of surimi gel,and the correlation between fish meat and surimi gel phospholipid and surimi quality,and finally selected the fish species suitable for making surimi.The main research contents and results are as follows:(1)In order to compare the differences of fatty acids in muscle of freshwater fish among families,orders and species,the crude fat of back muscle of 30 species of freshwater fish was extracted by chloroform-methanol(volume ratio=2:1).The composition of fatty acids in back muscle of 30 species of freshwater fish was analyzed by gas chromatography-mass spectrometry.The results showed that the content of crude fat was 50.24-174.96 g per kg muscle,the content of saturated fatty acid(SFA)ranged from 21.31% to 36.33%,the content of monounsaturated fatty acid(MUFA)ranged from 22.79% to 53.00%,and the content of polyunsaturated fatty acid(PUFA)ranged from 22.22% to 47.28%.A total of 25 fatty acids were detected in 30 freshwater fish species,including 8 saturated fatty acids,5 monounsaturated fatty acids and 12 polyunsaturated fatty acids.All 30 species of freshwater fish are rich in unsaturated fatty acids,and polyunsaturated fatty acids are the most abundant.(2)In order to establish a rapid and sensitive method for the determination of phospholipids in freshwater fish muscle,Ergthroculter ilishaeformis was used as an example to analyze by high performance liquid chromatography-evaporative light scattering detection(HPLC-ELSD).The Chromolith Performancen-ce-Si normal phase silica gel chromatography(100 mm × 4.6 mm)is used as the separation column.The n-hexane-isopropanol-13% acetic acid solution is a mobile phase system with ternary gradient elution.The flow rate is 1.5 mL/min,the column temperature is 30 ?,the injection volume is 20 ?L,the evaporative light scattering detector drift tube temperature is 70 ?,and the atomization gas(nitrogen)pressure is 320 kPa.The results showed that all the phospholipid components could be separated completely,and the peak area of each phospholipid component had a good linear relationship with the concentration in the corresponding range.The method has high precision,and C.V.value is less than 3.0%.The average recovery is 88.38%-107.41%,and RSD is 0.4%-4.95%.The method is simple,rapid,sensitive,accurate and reliable.It is suitable for the determination of phospholipids in freshwater fish such as Ergthroculter ilishaeformis.(3)In order to study the content and species of muscle phospholipids in freshwater fish,chloroform-methanol extraction method and HPLC-ELSD method were used to determine muscle phospholipids in freshwater fish.The results showed that the content of total phospholipids in freshwater fish muscle was 0.60-3.70 mg/g,and phospholipid ethanolamine(PE)accounted for 46.45%-65.30% of total phospholipids,which was the main component of muscle phospholipids in freshwater fish.Seven kinds of phospholipids were detected in all freshwater fish muscles,including phosphatidylethanolamine(PE),lysophosphatidylethanolamine(LPE),phosphatidylinositol(PI),phosphatidylserine(PS),phosphatidylcholine(PC),sphingomyelin(SM)and lysophosphatidylcholine(LPC).Among them,Micropterus salmoides,Megalobrama amblycephala,Hypophthalmichthys nobilis,Oreochromis mossambicus,Ctenopharyngodon idellus C.et V,Ctenopharyngodon idellus and Hypophthalmichthys nobilis have the richest phospholipid composition.(4)In order to screen fish species suitable for surimi,different kinds of freshwater fish meat were processed into a surimi gel through a series of processing steps.The gel strength,texture,whiteness,water holding capacity,crude fat content,phospholipid composition and content were determined,and the correlation between fish meat and fish paste gel phospholipid and surimi quality was also investigated.The results showed that the hardness of freshwater surimi gel was 121.83-972.9 g,cohesiveness was 0.03-2.35,elasticity was 1.35-2.95 mm,and chewiness was 0.21-8.37 mJ.The gel strength was 109.83-884.88 g.cm,whiteness was 66.02-80.8,and water holding capacity was 71.5%-91.83%.The crude fat content was 37.19-130.35 mg in each Kg surimi gel.According to the correlation between fish phospholipid,surimi gel phospholipid and surimi quality,considering all kinds of factors,it is concluded that Ctenopharyngodon idellus,Hypophthalmichthys nobilis,Oreochromis mossambicus,Hypophthalmichthys molitrix and Cirrhinus molitorella are the most suitable fish species for surimi production. |
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