Study On Physicochemical Properties Of DHA/EPA In Liposomal Model System

Some of lipids from aquatic organisms such as fish oil and algae oil are rich in n-3 polyunsaturated fatty acids,while DHA and EPA are the most typical two kinds of n-3 polyunsaturated fatty acids,which are characteristic active substances of aquatic products.Due to their abundant physiological effects,they have received extensive attention from academia and industry.However,DHA and EPA are highly susceptible to oxidation and rancidity,giving off an unpleasant fishy odor with low rate of bioavailability,digestion and absorption,thus the application of them were limited in academia research and industry.Research on its micro-nanostructure and functional mechanism of action has not yet appeared.Liposomes are a good carrier for DHA and EPA due to their unique stability in high water activity systems and their cell membranes-like phospholipid bilayer structures.This study focuses on the physicochemical properties of DHA and EPA in liposome model systems.Firstly,the effects of different solvents,different spinning speeds and different material ratios on film formation and hydration during DOPC/DHA/EPA liposome preparation were observed.Different scales of DOPC/DHA/ were prepared by extrusion method.Then their physicochemical properties were explored.Subsequently,fish oil liposomes of different scales were prepared with DOPC and soybean phospholipid as raw materials,and the contents of DHA,EPA and ARA were compared over time.Different scales of fish oil liposomes were applied to the preparation of yoghurt to evaluate its effect on the quality of yoghurt.The main findings are as follows:1.Ethanol was used as a solvent for dissolving DOPC/DHA/EPA in liposome preparation for rotary evaporation,which has good film formation and hydration effects.Rotating speed has no obvious effect on hydration.The suitable mass ratio of DOPC: DHA: EPA is 16:1:1.Under such conditions,nanoliposomes whose average particle diameter was between 77 nm to 205 nm can be constructed.The homogeneity of DOPC/DHA/EPA liposomes decreases with increasing scale and the zeta potential increases with increasing scale;The unloaded DOPC liposome has a significantly lower zeta potential than the DOPC/EPA-added DOPC liposome.and it can be seen that the addition of DHA and EPA can increase the quantity of electric charge of the system.2.The centrifugal stability of DHA and EPA liposomes decreased slightly with increasing scale,both above 95%;The DOPC/DHA/EPA liposomes after three days of incubation at 62 °C produced more characteristic oxidation products than the three-day refrigerated conditions,indicating that heating had an adverse effect on the oxidation resistance of DOPC/DHA/EPA liposomes.In the DOPC-fish oil system,the free DHA/EPA/ARA content generally attenuated with the prolongation of heating time,and the decay rate was slower from faster.In fish oil liposomes with smaller scales,The decay rate of free DHA/EPA/ARA is lower than that of the larger scale.It can be speculated that the decomposition rate of DHA/EPA/ARA triglyceride in fish oil is faster than that of free DHA/EPA/ARA in larger scale DOPC liposomes;Under the system of soybean phospholipid-fish oil liposome,the content of free DHA/EPA/ARA in the four scales of liposome fluctuated with each other.It can be speculated that complex lipid molecular species in soybean phospholipids have an effect on the decomposition and oxidation of DHA/EPA/ARA in the system.3.fish oil liposomes of different scales were prepared by extrusion method and their appearance and particle size distribution were characterized.The liposomes were applied in yogurt preparation and the effects of fish oil liposomes with different scales on the quality of yogurt were compared.The results showed that the scale of fish oil liposomes could be regulated by extrusion method and the appearance was uniform milky white with a good particle size distribution.The yogurt after fermentation with different scales of fish oil liposomes can be coagulated well and its appearance is not significantly different from that of the control yoghurt;The fish oil liposomes of smaller scale can make the p H and water retention of the yogurt change less which also have a better protection on DHA and EPA in yogurt;After 7 days of refrigeration,the yogurt odor with different additions of fish oil liposomes showed some difference.After 14 days of refrigeration,the odor of yogurt with additions of fish oil liposomes had no significant difference while there were significant differences in odor between the control groups.The study concludes that: the physicochemical properties of DHA and EPA are slightly different under the liposome model system with different scales and media.The effect of different scales of soybean phospholipid-fish oil liposome on the odor quality of yogurt increases over time.It will lay the foundation for further study on the mechanism of the relationship between micro-nano structure and function of the characteristic active substances in aquatic products,and on the high value utilization of aquatic resources.