Preparation Of Polyunsaturated Fatty Acid Ethyl Esters From Chia Seed Oil

Chia seeds are novel food ingredient which was authorized by the People's Republic of China National Health and Planning Commission in 2014.Chia seeds contain about 25%?38%oil by weight,which are mainly polyunsaturated fatty acids?PUFAs?.The linoleic acid and?-linolenic acid are the most abundant comprising more than 60%of total oil,which play an important role in preventing cardiovascular and cerebrovascular diseases,lowering blood pressure,regulating the level of blood lipids and so on.Therefore,the chia seed oil was used as raw material to prepare and separate PUFAs for obtaining high purity linoleic acid and?-linolenic acid.The main results were as follows:?1?The basic components of chia seeds were determined respectively.Chia seeds exhibited the following chemical characteristics,and percentages reflect mass percentage per 100 g of chia seeds.Moisture and ash composed?5.94±0.02?%and?4.79±0.03?%of the total mass.The total lipid component was?35.28±0.50?%,and protein was constituted?20.60±0.40?%of the seeds.The total dietary fiber was valued?33.25±1.10?%.The effects of roasting conditions on the physicochemical properties and fatty acids composition of pressed chia seed oil were investigated.With the increase of roasting temperature and time,the results of acid value,peroxide value and UV absorbance of the oil showed an upward trend,and the roasting at 180? for more than 50 min was significantly different from other conditions?p<0.05?.The oil yield of chia seeds was significantly improved under high temperature?p<0.05?,but the chia seeds were easier to produce a burnt smell,resulting in a deeper color,and part of the oil presented with dark brown.There was no effect on fatty acid profiles.For the content of fatty acids,the effect was not significantly while under different roasting conditions.Therefore,the roasting of chia seeds should not be carried out at high temperatures.It was recommended that when roasting at 180?,time should be less than 50 min.?2?The chia seed oil was obtained by pressing and then the physicochemical properties of oil were characterized.The results showed that the acid,peroxide,saponification and iodine values and unsaponifiable matter content of chia seed oil were 0.38 mg?KOH?/g,0.24 mmol/kg,210.70 mg?KOH?/g and 195.61 g?I₂?/100 g,respectively.The average relative molecular mass is 802.The fatty acid ethyl esters were synthesized by alkali catalysis for its lower acid value of chia seed oil.The catalytic effects of sodium methoxide,sodium ethoxide and NaOH were evaluated through the conversion rate and yield of fatty acid ethyl esters.The yield and ethyl esters conversion rate were the highest when catalyzed by NaOH,and the yield was significantly different from the other two groups?p<0.05?.Choosing NaOH as catalyst to optimize the process for the preparation of fatty acid ethyl esters,the effects of transesterification temperature,transesterification time,molar ratio of ethanol to oil and catalyst dosage on the transesterification of chia seed oil were investigated by single factor and orthogonal experiments.The results showed that when the transesterification temperature was80?,the transesterification time was 1.5 h,the molar ratio of alcohol to oil was 9:1,and the amount of catalyst was 0.6%of oil weight,the ethyl esters conversion rate of chia seed oil can reach 89.01%.?3?Using the fatty acid ethyl esters as raw material,the polyunsaturated fatty acid ethyl esters in chia seed oil were prepared and separated by urea inclusion.Through the single factor and orthogonal experiments,the optimal parameters of separation process determined were as follows:fatty acid ethyl esters-to-urea ratio of 1:3?m/m?,fatty acid ethyl esters-to-95%ethanol ratio of 1:8?m/v?,crystallization temperature of-10? and crystallization time of 15 h,the purity of linoleic acid ethyl ester in the isolated product was increased from the initial 18.82%to 20.28%,the content of?-linolenic acid ethyl ester was increased from 64.24%to 77.91%,and the total polyunsaturated fatty acid ethyl esters content was increased from 83.06%to98.19%,respectively.In addition,the separated samples were analyzed by GC-FID.The results showed that the separated samples mainly contain polyunsaturated fatty acids ethyl esters which consisting of linoleate acid ethyl ester and?-linolenic acid ethyl ester.FT-IR,XRD and SEM were used to characterize the urea inclusion compounds.The results showed the formation of urea inclusion compounds with hexagonal prism structure.The DPPH·and ORAC radical scavenging methods were used to evaluate the antioxidant activity of the polar,non-polar and total components of crude oil and ethyl esters.All polar,non-polar and total components of chia seed oil showed higher antioxidant activity,so in order to prevent oxidation of polyunsaturated fatty acid ethyl esters in application,it is necessary to take relevant measures to ensure product quality and extend the shelf life.