Study On Antioxidant Activity Of DHA Algae Oil And Its Oxidative Kinetics

DHA?Docosahexaenoic acid?is of importance?-3 long-chain polyunsaturated fatty acid,which plays a vital role in infant intelligence and vision development,prevention of cardiovascular and cerebrovascular diseases,anti-cancer,and so on.Since the content of unsaturated fatty acids in DHA algae oil is up to 60%,it is sensitive to light,heat,metal ions and other factors.DHA is susceptive to oxidation,and losses of economy and hazards on human health are great problem.In this study,DHA algae oil was used as raw material to study the effects of natural phenolic antioxidants and compounds of soybean lecithin on the oxidation stability of DHA algae oil by Schaal oven accelerated oxidation method.The oxidation stability of DHA algae oil under different storage temperature was studied and the oxidation kinetics model of POV,p-AV,CD and TBA of DHA algae oil with storage time and temperature were performed.In addition,DHA algae oil microcapsules were prepared by complex coacervation method,and the storage stability of DHA algae oil microcapsules was studied,which can provide references for the development and utilization of DHA algae oil.The main results are as follows:?1?The antioxidant activity of caffeic acid and ferulic acid was evaluated in vitro using three models of antioxidant including DPPH free radicals scavenging activity,ABTS free radicals scavenging activity,ferric reducing ability and reducing ability.The antioxidant of caffeic acid and ferulic was compared with L-Ascorbic palmitate and BHT respectively.The results indicated that caffeic acid had strong antioxidant activities on scavenging DPPH free radicals,and the inhibition rate was higher than ferulic,BHT and L-Ascorbic palmitate.Caffeic acid and had the strongest ability on scavenging ABTS free radicals,ferric reducing ability and reducing ability,L-Ascorbic palmitate had the weakest ability on scavenging ABTS free radicals,and ferulic gave the modest reducing ability,respectively.The antioxidant activity of phenolic compounds mainly depended on the number of phenolic hydroxyl groups and the position in the chemical structure.?2?The influence of different antioxidants on the oxidative stability of DHA algal oil was studied by Schaal oven method with peroxide value?POV?,conjugated diene?CD?,P-anisamide and thiobarbituric acid?TBA?as indexs of oxidation stability.Gas chromatography was conducted to analyze the changes of fatty acid composition during the storage of algal oil.The results showed that caffeic acid and ferulic acid had a strong inhibitory effect on the oxidation of algal oil,and the antioxidant activities were as follows by caffeic acid,BHT,ferulic acid and L-ascorbyl palmitate.Therefore,caffeic acid and ferulic acid can be used as natural antioxidants in the oil industry.?3?The antioxidation activity of soybean lecithin on DHA algal oil was studied by Schaal oven oxidation test and Rancimat.The L₉?3⁴?orthogonal test was applied to optimize the combination of antioxidants on the basis of protection factor?PF?value with Rancimt.The peroxide value?POV?of DHA algal oil with or without optimized antioxidants were compared by Schaal test.The results indicated that soybean lecithin had antioxidant effect on DHA algal oil and dose-effect relationship.With addition of0.02%V_E,0.02%L-ascorbyl palmitate and 0.04%soybean lecithin could prolong the shelf life of DHA algal oil from 96 days to 192 days at 20?.Hence,soybean lecithin had excellent antioxidant effect.?4?The oxidation stability of DHA algae oil under different storage temperature was studied and the oxidation kinetics model of POV,p-AV,CD and TBA of DHA algae oil with storage time and temperature were performed.The results indicated that the oxidative rancidity of DHA algae oil aggravated with the increase of time and temperature.The oxidation kinetics model of DHA algae oil accorded with the first-order kinetics model.The correlation coefficients of oxidation kinetics models of POV,p-AV and TBA were higher than 0.96,which provides a theoretical reference for predicting and monitoring the quality of DHA algae oil.?5?Whey protein isolate?WPI?and gum arabic?GA?were used as wall material to encapsulate DHA algae oil by complex coacervation,and subsequently dried using freeze drying to obtain microcapsules.The process of WPI/GA complex coacervation was optimized by Zeta potential,turbidity and morphology of microcapsules,and the oxidation stability of DHA algae oil microcapsules was studied.The results indicated that peroxide value of DHA algae oil encapsulate and blank group increased from 1.00 mmol/kg to 11.68mmol/kg and 20.42 mmol/kg,respectively.Hence,microencapsulated DHA algae oil can effectively improve the oxidation stability of DHA algae oil.