Preparation And Stability Of Peony Seed Oil Microemulsion

According to statistics from the National Data Network,as of 2019,edible vegetable oil imports were 9.53 million tons,an increase of 51.51%over the same period in 2018.The insufficient self-sufficiency rate of edible oil seriously threatens the safety of edible vegetable oil.Peony seed oil is a new type of oil crop.The yield of peony seeds is 3.4times that of soybeans and 1.4 times that of rapeseed.Therefore,the development of peony seed oil is of great significance to improve the oil supply capacity and resist the impact of foreign oils on the domestic market.Peony seed oil has an optimal proportion of fatty acid structure and contains a large amount of active substances.Peony seed oil has high nutritional value and can be widely used in medicine,health food,advanced cosmetics,lubricants and other industries,and has great development potential.However,because peony seed oil is highly unsaturated,it is susceptible to heat,light,and metal ions during storage,transportation,and sales.Oxidative rancidity will affect its nutritional value.Therefore,it is important to solve or slow down the oxidation of peony seed oil,which will promote the development and application of peony seed oil.In this paper,the formula composition and the best preparation method of peony seed oil microemulsion are studied and discussed.Appearance observation method and pseudo-ternary phase diagram method were used to select the best surfactant.The effect of different hydrophilic-lipophilic balance values and different coemulsifiers,surfactants,and co-surfactant ratios on the formation of microemulsions determines the composition of peony seed oil microemulsions;the different addition order,temperature and salinity affect the microemulsion formation.The effect of the emulsion determines the final preparation method.The conductivity,laser particle size analyzer and gas chromatograph were used to determine the physical and chemical properties and stability of the peony seed oil microemulsion.The stable peony seed oil microemulsion was obtained and can be stored for a long time.The main findings are as follows:1.Preparation of peony seed oil microemulsionThe microemulsion of peony seed oil was prepared by phase change point observation method and pseudo-ternary phase diagram method.Researched different surfactants,hydrophilic-lipophilic balance（HLB value）,co-surfactant and mixed surfactant ratio（Km value）,selected the best component,and studied different addition order,temperature Effects of salinity and salinity on microemulsion formation of peony seed oil.The system composition of peony seed microemulsion is determined as:peony seed oil/Tween 80/span 80/anhydrous ethanol/water,the order of addition is to first mix the mixed surfactant and peony seed oil,and add water dropwise at a fixed speed.In addition,through orthogonal experiments of the mixed surfactant HLB value,the mixed surfactant and co-surfactant ratio Km value,and the preparation temperature,we can know that the optimal component ratio condition is:normal temperature（25℃）,The HLB value of the mixed surfactant is 11 and the Km value of the co-surfactant is 1.Experiments show that the presence of low concentration of salt ions can promote the formation of microemulsion in peony seed oil,but when the concentration of salt ions is too high,the formation of microemulsion can be inhibited due to the"salting out"phenomenon.Therefore,during production and processing,peony seed oil microemulsion will be more suitable for foods with lower salt ion concentration.It can be used as a reference for future storage stability.2.Physicochemical properties and stability of peony seed oil microemulsionElectrical conductivity was used to determine the type of peony seed oil microemulsion,while particle size and other physical and chemical properties were measured.The results show that the peony seed oil microemulsion is an oil-in-water（O/W）type microemulsion with an average particle size of 41 nm.The PDI value is stable at about 0.218,the conductivity is about 682 m S·cm^-1,and the p H value is stable at6.7-6.8.The appearance of the prepared peony seed oil microemulsion was a pale yellow transparent liquid.At the same time,centrifugal stability test,high temperature test（60℃/14 day）,accelerated test（30℃/3 months）and sample retention observation test（5℃/3 months and 25℃/3 months）were carried out.The experimental results of micro peony seed oil showed that the microemulsion of peony seed oil can maintain a clear and transparent appearance without centrifugation at 3000 rpm for 30 min.The centrifugal stability is good.The acid value and peroxide value of peony seed oil in the high temperature test on day 14 were 1.396 g KOH/mg Oil,0.1117 g/100g,both lower than 1.898 g KOH/mg Oil,0.134 g/100g peony seed oil.The retention of linoleic acid and linoleic acid in peony seed oil was 40.66%and 15.51%on the 14th day,which was higher than 16.35%and6.54%of peony seed oil.In the third month,the retention rates of linolenic acid and linoleic acid were 40.36%and 16.51%respectively,which were higher than 17.59%and11.84%of peony seed oil.Sample retention observation The retention rate of linolenic acid and linoleic acid in peony seed oil in the accelerated test of microemulsion in the third month was 42.36%and 19.74%at 5℃,which was higher than 25.21%and 13.42%;under the storage condition of 25℃,the microemulsion of peony seed oil accounts for40.21%and 18.38%respectively,which is higher than 20.84%and 11.59%of peony oil respectively.In summary,under the same test conditions,the retention of linolenic acid and linoleic acid in the microemulsion of peony seed oil is higher than that of peony seed oil.Peony seed oil microemulsion has better thermal stability than peony seed oil.After emulsification,peony seed oil has better storage stability and better storage effect under cold storage conditions（5℃）.