Stability Study Of Flaxseed Oil Nanoemulsion

Flaxseed oil is rich in polyunsaturated fatty acids,with high nutritional value and a variety of bioactive functions,but the high content of polyunsaturated fatty acids also makes flaxseed oil more prone to oxidative rancidity,reducing its quality and limiting its development,nanoemulsion embedding system to solve the poor oxidative stability of flaxseed oil and other problems to provide a scientific approach.In this study,the changes of oxidation indexes of flaxseed oil during storage were measured by accelerated oxidation test system,and an oxidation kinetic model of flaxseed oil was constructed to predict the shelf life;subsequently,fat-soluble antioxidants were selected and added to flaxseed oil to extend its shelf life.The physical stability and oxidative stability of flaxseed oil nanoemulsions were investigated under different storage and processing conditions by characterization of particle size,potential,color difference,delamination index,rheological properties,microscopic morphology,and physicochemical indexes,and the shelf life of flaxseed oil nanoemulsions was also measured by accelerated oxidation test to construct a shelf life model.The aim is to provide a theoretical reference for the design and preparation of flaxseed oil nanoemulsions and a scientific way to improve the oxidative stability of flaxseed oil.The main findings are as follows.(1)The changes in oxidative stability and shelf life of flaxseed oil during accelerated oxidation and after the addition of antioxidants were mainly investigated.The results showed that temperature had a dramatic effect on the oxidation index of flaxseed oil,and the peroxide value,acid value and thiobarbituric acid value changed sharply with the increase of temperature during 36 days of storage.The shelf-life model of flaxseed oil was constructed based on the change of peroxide value,and the shelf-life of flaxseed oil was predicted to be 33.64 days,31.79 days and 30.11 days at20 ℃,25 ℃ and 30 ℃,which had less error with the measured values.In addition,the selected fat-soluble antioxidants could effectively extend the shelf life of flaxseed oil with the formulation of tea polyphenol palmitate 0.21 g·kg-1,rosemary extract 0.45g·kg-1 and citric acid 0.20 g·kg-1.(2)The main study was on the preparation process of flaxseed oil nanoemulsion,using flaxseed gum as surfactant,and the optimal preparation process was determined by single-factor and response surface optimization tests.The results showed that the preparation process of flaxseed oil nanoemulsion was 0.95% mass fraction of flaxseed gum,7.7% mass fraction of flaxseed oil,109 Mpa mean pressure and 2 times mean number of times.(3)The effects of different storage temperatures,p H,Na Cl and sterilization conditions on the physical stability of flaxseed oil nanoemulsions were mainly studied in terms of Particle size,ζ-potential,Color difference,Creaming index,Rheological properties and Micromorphology.The results showed that the stability of nanoemulsions was strongly affected with the increase of storage temperature;under different p H conditions,the characterization of p H 5 and p H 7 were less different from the control group and had better stability,while on the contrary,the stability of nanoemulsions was poor at p H 3 and alkaline conditions;with the increase of ionic strength,unstable aggregation occurred at high ionic strength(Na Cl > 200 mmol/L);The best stability was observed after ultra-high temperature transient sterilization treatment.The results indicated that the physical stability of flaxseed oil nanoemulsions was better under low temperature,neutral or weak acidic,low ionic concentration and ultra-high temperature transient sterilization conditions,and these results provided theoretical support to promote the stability of flaxseed oil nanoemulsions during storage and processing.(4)The oxidative stability of flaxseed oil nanoemulsions was measured by POV and TBARs under different temperatures,packaging materials,light,sterilization treatment and addition of antioxidants,and compared with flaxseed oil to investigate the effect of nanoemulsion encapsulation system on the oxidative stability of flaxseed oil.The results showed that the oxidative stability of flaxseed oil nanoemulsions varied significantly at different temperatures,with better stability at 30 ℃ and significantly lower values of POV and TBARs compared with flaxseed oil;the quality of flaxseed oil nanoemulsions stored in containers of different materials was the best in ceramic jars,followed by glass bottles,plastic bottles and the worst in iron cans;the effect of light on oxidative stability is significant,with stability in the order of light avoidance > natural light > fluorescent light;after different sterilization treatments,oxidation stability is better for ultra-high temperature instantaneous sterilization,the worst for pasteurization;in short,flaxseed oil should be stored at low temperature;storage conditions as far as possible to choose light and away from the iron bottle.Similarly,setting POV up to 9.85 mmol/kg as the end point of shelf life,the shelf life of flaxseed oil nanoemulsions were obtained as 53.79 days,50.77 days and 47.93 days at 20 °C,25 °C and 30 °C,while the shelf life of flaxseed oil was33.64 days,31.79 days and 30.11 days at 20 °C,25 °C and 30 °C.It showed that the flaxseed oil encapsulation system extended the shelf life of flaxseed oil and significantly improved the oxidative stability of flaxseed oil.