Effect Of Processing On Beneficial Lipid Phytochemical And Antioxidant Activity Of Flaxseed Oil

Flaxseed oil is an edible oil rich in polyunsaturated fatty acid,so beneficial lipid phytochemicals and antioxidant activity are vital for the quality of flaxseed oil.This study compared the values of beneficial lipid phytochemicals and antioxidant activity of the collected flaxseed oil samples from different representative origins in order to select the most suitable flaxseed for next research period.Then,it was needed necessarily to investigate the effect of oil extraction methods and pretreatment temperatures on beneficial lipid phytochemicals and antioxidant activity of the flaxseed oil samples produced from seed screened in last research.For providing theoretical guidance for the production of flaxseed oil,a comprehensive evaluation based on those results was required using Principal Component Analysis.Firstly,values of beneficial lipid phytochemicals and antioxidant activity of 10 flaxseed oil samples on sale produced from flaxseeds from different regions in four countries were analyzed.It was indicated that the Xinjiang flaxseed oil sample had the high levels of beneficial lipid phytochemicals and antioxidant activity in total.The flaxseed oil contained the highest level of tocopherol,polyphenol and flavonoid,with its level of phytosterol(3600.36 mg/kg)only next to the oil sample having the highest content of phytosterol(3868.85 mg/kg),especially some phytosterol individuals contents even being in the first place,such as cycloartenol,?5-avenasterol and stigmasterol.As for antioxidant activity of oil samples,the oxidative stability index,DPPH and ABTS scavenging capacities of polar phytochemicals and DPPH scavenging capacity of the whole oil in Xinjiang flaxseed oil were on the top,meanwhile its values of FRAP and ORAC scavenging capacity of polar phytochemicals and DPPH scavenging capacity of the non-polar phytochemicals were just slightly lower than the highest levels.Next,an evaluation on beneficial lipid phytochemicals and antioxidant activity of coldpressed,hot-pressed,solvent-extracted seed oil and solvent-extracted cold-pressed cake oil,solvent-extracted hot-pressed cake oil was conducted to investigate the effect of extraction methods on the quality of flaxseed oil.It was shown that each extraction method had its advantage.The value of tocopherol(614.11 mg/kg)in the solvent-extracted flaxseed oil was found extremely higher than that in cold-pressed(563.58 mg/kg)and hot-pressed seed oil(483.35 mg/kg);the values of phytosterol and flavonoid in cold-pressed seed oil topped the list;it may be more beneficial to the release of polyphenol that making a thermal treatment on flaxseed,with the content in hot-pressed oil higher than other oil samples from 12.63% to 80.17%.Besides the advantages in beneficial lipid phytochemicals,it was found that the highest value of oxidative stability index and the strongest free radical bleaching capacity of polar phytochemicals were determined in the hot-pressed seed oil,while in the capacity of DPPH scavenging of non-polar and the whole oil,cold-pressed seed oil was found on the top.However,it was also presented that the solvent-extracted cake oils were weak at the level of beneficial lipid phytochemicals and free radical scavenging capacity in total.Then,an comparison around beneficial lipid phytochemicals and antioxidant activity of hot-pressed seed oils with seeds roasted at 100℃~180℃ and solvent-extracted seed cake oils was made to systematically validate the effect of pretreatment temperatures on the quality of flaxseed oils.It was shown that 100℃ and 120℃-roasting were beneficial to the increase of tocopherol,with the content of tocopherol in 120℃ hot-pressed oil was 1.26 times higher than that in 140℃ hot-pressed oil.The values of phytosterol,polyphenol and flavonoid in flaxseed oils and cake oils was found being fluctuated as flaxseed pretreatment temperatures rising.It were found that the changes in hot-pressed seed oils or solvent-extracted cake oils were dissimilar.It was found that the levels of total phytosterol in hot-pressed seed oils and solvent-extracted cake oils varied from 7528.75 mg/kg to 11287.30 mg/kg and from 1453.65 mg/kg to 2728.21 mg/kg,with the highest level found in 120℃ hot-pressed seed oil and 160℃ solvent-extracted cake oil respectively.It was determined that the values of polyphenol and flavonoid in 180℃ and 120℃ hot-pressed seed oil was 2.23 and 1.48 times folder than the lowest level respectively,while the 160℃ solvent-extracted cake oil contained the highest value of polyphenol and flavonoid.For free radical scavenging capacity,the strongest scavenging capacities were detected in 180℃ hot-pressed seed oil,but no obvious regulation was found in the data of solvent-extracted flaxseed cake oils.Finally,a comprehensive evaluation was made on beneficial lipid phytochemicals and antioxidant stability using Principal Component Analysis.It was indicated that the grades hotpressed flaxseed oils got varied from-0.507 to 3.197,totally higher than the grades of other oil samples(-2.887-2.057),especially the highest grade was scored by the flaxseed oil produced from flaxseed roasted at 180℃,even with 0.828 point higher than the highest grade of flaxseed oil on sale(2.369).