Lipid Fractions Analysis Of Fish Oil And The Study On Enrichment And Separation Of OPL/OPO Structural Lipids

There are abundant aquatic products in Hainan Province.Fish and its processing byproducts are rich in lipids and other bioactive components,which are widly comsumed by human.However,there is insufficient research on the lipid nutrition of fish.Therefore,tilapia(freshwater aquaculture),golden pompano(mariculture)and round scad(marine fishing)were selected as the research materials in this study.The lipidomics methods were used to analyze the fatty acid and lipid profiles.Besides,the fatty acid composition and distribution in triacylglycerol(TG)of fish lipids were compared with those of human milk fat and commercially OPO-containing infant formula fat to evaluate the differences and similarities between fish lipids and human milk fat.This study was aimed to provide theoretical support for the further processing of fish and the application in human milk fat substitutes.First,the Folch method was used to extract lipids from tilapia(muscle,head,and viscera),golden pompano(muscle,head,and viscera)and round scad(muscle,head,and viscera).Gas chromatography was applied to analyze the composition and contents of total fatty acids.Second,six lipid fractions were separated by solid phase extraction and their fatty acid composition was determined individually.The esterification positions of fatty acids in TG and phospholipids(PL)were analyzed.Then,the OPL/OPO contents in fish lipids were determined.The lipid species were determined by UPLC-Q-TOF-MS.The fatty acid and lipid profiles were systematically analyzed.Afterwards,a solvent fractionation method using isopropyl alcohol was optimized to enrich the OPL/OPO structural lipids from golden pompano lipids Finally,the differences and similarities of fatty acid composition and positional distribution in TG between fish lipids,human milk fat and commercially OPOcontaining infant formula fat were analyzed,thereby evaluating the potential of fish lipids as a source for human milk fat substitutes.The results were as follows:(1)Tilapia,golden pompano and round scad had low lipid contents,n-6/n-3 PUFA values and cholesterol contents,so they were suitable for human consumption.Besides,the head and viscera were rich in lipids and fatty acids,which could be further exploited.(2)The TG fraction of tilapia,golden pompano and round scad was the major composition,which occupied 48.56-89.36%,78.33-89.83% and 61.34-78.08% of total lipids,respectively;the viscera of tilapia and golden pompano were rich in saccharolipids(SL)+PL,which occupied 16.24% and 9.84%,respectively.The SL+PL content(24.21%)in round scad muscle was the highest.Compared with other lipid fractions,PL contained the highest percentage of DHA,accounting for 8.36-14.88%,9.89-20.74% and 13.06-16.53% of total fatty acids,respectively.(3)The characteristics for fatty acids distribution in TG and PL were observed in this study.In terms of TG,saturated fatty acids(SFA)and DHA of tilapia and golden pompano were mainly distributed in the sn-2 position,while monounsaturated fatty acids(MUFA),polyunsaturated fatty acids(PUFA),n-3 PUFA and n-6 PUFA were mainly distributed in the sn-1,3 positions,which was accorded with the structural characteristics of sn-USU structural lipids.In round scad,MUFA were mainly distributed in the sn-1,3 position,while PUFA,n-3 PUFA and DHA were mainly distributed in the sn-2 position.In terms of PL,SFA were mainly distributed in the sn-2 position,while PUFA,n-3 PUFA,n-6 PUFA and DHA were mainly distributed in the sn-1 position.(4)Totally,349,382 and 414 lipid species were identified in tilapia,golden pompano and round scad,respectively.Furthermore,21,27 and 34 species of lipids were considered as potential lipid classifiers using multivariate statistical analysis for the three parts of tilapia,golden pompano and round scad,respectively.(5)The optimum solvent fractionation conditions for golden pompano lipids were as follows: fractionation temperature was-12 °C,solid-liquid ratio was 1:4,and fractionation time was 4 h.Under these conditions,the content of OPL+OPO was 305.18 mg/g TG,which was increased by 94.18% compared with the initial golden pompano lipids.(6)The lipids from basa fillets,tilapia muscle and golden pompano were similar to human milk fat in terms of TG fatty acid composition and positional distribution.The mixture of basa fillets lipid and fractionated golden pompano lipid would be more similar to the breast milk fat in OPL/OPO content.