| Oil peony is a new woody oil crop,which has aroused a research upsurge in recent years.However,there are few researches on the seed oil of Paeonia Ludlowii,a plant endemic to Tibet.In this study,cold pressing method and organic solvent extraction method were used to extract and refine Paeonia Ludlowii seed oil,and the important effects of extraction method and refining technology on the biological physicochemical properties,fatty acid composition,aroma composition and in vitro antioxidant tolerance of Peony seed oil were explored.Moreover the effect of different storage time on the fatty acid composition,nutrients and natural antioxidants on the shelf life of peony seed oil was studied;and the total phenols,antioxidant activities and secondary metabolites of four peony cultivars were compared and analyzed.The results showed:First,the oil yield of Paeonia Ludlowii seed oil extracted using two methods was analysed,the results showed that organic solvent extraction produced the highest oil yield(29.2%)and cold pressing producing the lowest(23.6%).Second,we also analyzed and evaluated physicochemical properties,The refining process has no significant variations in refractive index among two extracted oils,while considerable variations in acid value,peroxide value、iodine value and color.Press extraction: Iodine value was 140 g I/100 g after decolorization,acid value was 0.36 mg KOH/g after deacidification,peroxide value was 1.89 mmol/kg after deacidification,and then 0.76 mmol/kg after decolorization.Saponification value was 182 mg/g after deodorization,and there were significant differences(P<0.05).Solvent extraction: Iodine value was 158 g I/100 g after decolorization,acid value was 0.35 mg KOH/g after deacidification,peroxide value was 1.57 mmol/kg after deacidification,and then 0.85 mmol/kg after decolorization,saponification value was 176mg/g after deodorization,and there were significant differences(P<0.05).The appearance color of peony seed oil extracted by cold pressing method is dark yellow,and the oil obtained after deodorization is almost colorless and odorless.Third,the two extraction methods have no significant effect on the composition and relative content of the main fatty acids of Paeonia ludlowii seed oil.However,compared with the solvent extraction method,the fatty acid content of the extraction method of Paeonia macroflorum seed oil fluctuated less in the refining step and was more stable.According to GC-MS analysis,the relative contents of unsaturated fatty acids and saturated fatty acids were about 87.51% and 12.49%,respectively.The relative contents of linolenic acid,oleic acid and linolenic acid were relatively large in the unsaturated fatty acids,and the contents of oleic acid,linoleic acid and linolenic acid were 42.25%,15.29% and 29.44%,respectively,while stearic acid and palmitic acid were the main components of saturated fatty acids.Forth,using headspace solid phase microextraction(HS-SPME)combined with gas chromatography-mass spectrometry(GC/MS)to analyze the aroma components of 10 seeds oil samples from different processing stages,a total of 29 volatile substances were detected,the Pressed oil after refining were detected in 15,16,16,18 and 15 aroma components,the method of solvent oil after refining respectively detected16,14,19,14 and 13 aroma components,the main volatile species each are not identical.As can be seen from the above analysis results,peony seed oil contains abundant volatile flavor substances,including styrene,benzaldehyde,nonanal,(E,E)-2,4-heptanedienal,4-methyl-2-pentone,benzyl alcohol,n-octanol,4-methyl-2-pentone,etc.Fifth,two natural antioxidants have a greater impact on the shelf life of Paeonia Ludlowii seed oil.The antioxidant effect is 0.04%tea polyphenols + crude oil > 0.04% bamboo leaf flavonoids + crude oil >crude oil,and the shelf life at room temperature 25℃ were Respectively200.73 d,134.90 d,131.61 d,In(IP)has a linear relationship with temperature,but the established equation can only be applied within a certain temperature range,and cannot accurately extrapolate and predict the temperature range outside the measured temperature range of Paeonia Ludlowii seed oil Shelf life.Sixth,in this study,the main fatty acid composition and content of 4 kinds of vegetable oils were analyzed,and 10 fatty acid compositions were mainly measured.The order of unsaturated fatty acid content was PO> PR> PD> PL.Among the four peony seed oils,only PO has a higher linoleic acid content than oleic acid,and other samples have higher oleic acid content.Moreover,in this study,the total phenols,antioxidant activities and secondary metabolites of different varieties of peony seed oil were analyzed.The order of flavonoid content of the four peony seed oils was PD > PL > PO > PR,and the order of total phenol content was PO > PR>PL> PD,According to the comprehensive comparative analysis,the antioxidant capacity of PO and PR in low altitude area is higher than PD and PL in high altitude area.ABTS,DPPH,and FRAP analysis show that the results are positively correlated with the results of total phenol content.Interestingly,the content of total flavonoids detected is weakly correlated with the three antioxidant activities.Therefore,we conclude that it is not flavonoids that play a major role in antioxidant capacity,but total phenols.In addition,the difference in antioxidant activity of different varieties of peony seed oil may also be related to some undetected or unconcerned chemical components.Other secondary metabolites such as phenols,flavonoids,esters,terpenes and other plants can accelerate the antioxidant activity of peony seeds.Therefore,based on UPLC-MS/MS detection technology,194 secondary metabolites were detected,with flavonoids and phenolic acids as the main secondary metabolites.The relative content of phenolic substances was found to be in the order of PL<PD<PO< PR,the results once again verified the above speculation,the antioxidant capacity of PO and PR in low altitude areas is excellent,and the antioxidant capacity of PD and PL in high altitude areas is poor,which may be related to the difference in the habitat of peony.In conclusion,each method has both advantages and disadvantages for two extraction of Paeonia Ludlowii seed oil.Cold pressing method has obvious advantages,such as low cost,convenient operation,the whole processing process is simple and safe,more suitable to extract high quality peony seed oil.And the refining process should select appropriate refining steps according to the quality of peony seed oil to maximize the retention of the dominant ingredients.Compared with the other three vegetable oils,the Paeonia Ludlowii seed oil is a potential candidate for a new and safe health care edible oil,and has broad application prospects for its development. |
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