| Star anise mainly produced in the southwest of China,which is an important wood flavor and widely used in food seasoning,Chinese medicine,etc.Star anise also is the main raw material for the extraction of aniseed and shikimic acid.In 2019,the production of star anise in Guangxi’s exceed 200000 tons,accounting for about 85% of the world’s.Star anise seeds account for about 20% of the quality of the whole fruit,star anise seeds are rich in oil and volatile components which are similar to the shells.They fall off by themselves during picking,curing,drying and drying of star anise,falled star anise seeds are generally discarded or used as fertilizer,resulting in a great waste of resources.In order to make effective use of star anise seed,this paper studied star anise seed oil.1.The study on the composition of star star anise seed oil(SAO)showed that there was no significant effection in the fatty acid composition of SAO in different extraction methods,but there was a significant effcetion in the content of fatty concomitant.The unsaturated fatty acids in the three kinds of SAO is about 80%(linoleic acid is 38.53-39.28%,oleic acid is 38.99-39.76%).SAO is rich in total phenols(35.687-48.842mg/100g),sterols(1450.125-1921.230mg/kg),and have a small amount of squalene and vitamin E,and has a strong antioxidant capacity.Soxhlet extraction anise seed oil(Soxhlet extractions star anise seeds oil,SE-SAO)with a total phenol,sterol,the advantage of high antioxidant capacity.2.Headspace Solid Phase Microextraction(HS-SPME)and Gas Chromatography-Mass Spectrometry(GC-MS)Compared the volatile components of three kinds of SAO and Star anise essential oil(EO).The aroma components of three kinds star anise seed oils were 91 volatile.There ara 58 kinds components were identified.in Cold press-Star aniseeds oil(CP-SAO),and71 volatile components in HP-SAO(Hot press-Star aniseeds oil).59 volatile components in SE-SAO.There are 38 kinds of common components,mainly aromatic species and terpenes species.HP-SAO and CP-SAO have a total of 50 components,and they have the same common components as EO(40).Principal component analysis showed that CP-SAO and EO had the most similar volatile components,followed by HP-SAO and SE-SAO.There were 39 characteristic aroma components in CP-SAO,43 in HP-SAO,and 28 in SE-SAO.The main substances in CP-SAO were trans-anethole,linalool,estragole and eucalyptol.In HP-SAO,trans-anethole,linalool,estragole,phenylacetaldehyde,3-ethyl-2,5-dimethyl-pyrazine,and eucalyptol play a leading role in the overall aroma.There are 5 kinds of components in SE-SAO: trans-anethole,estragole,linalool,eucalyptol and anisic aldehyde.3.Analyze the oxidation stability of SAO through the accelerated oxidation experiment of oven.(1)During the accelerated oxidation process,the Acid value of the three kinds of SAO showed a relatively slow increasing trend during 0-15 days,and the acid prices of CP-SAO and HP-SAO increased faster during 15-30 days,HP-SAO acid prices reached the highest at 30 days.The peroxide values of three kinds of SAO increased obviously in the 0-20 days,and the peroxide values of CP-SAO> HP-SAO>SE-SAO increased slowly after 20 days.The thiobarbituric acid values of the three SAOs in 0-30 were CP-SAO > SE-SAO > HP-SAO.Among the three oil samples,the content of tocopherol in CP-SAO decreased fastest,followed by HP-SAO and SE-SAO.By the 10 th day,the tocopherol in CP-SAO had been completely degraded,and no tocopherol could be detected in the three oils on the 15 th day.(2)The infrared spectrum of SAO with three different extraction methods is shown,the peak spectra of SAO were different with different extraction methods.The infrared spectra of the SAO by three different extraction methods showed that there were different in the oxidation process of SAO.The peak intensity of CP-SAO reached the maximum at 20 days,HP-SAO reached the maximum at about 25 days,the SE-SAO reached the maximum at 30 days.(3)Through the analysis of fatty acids in the oxidation process of SAO,the percentage of CP-SAO,HP-SAO and SE-SAO linoleic acid in the accelerated oxidation process of aniseed oil decreased by 49.82%,37.98% and 39.39%,respectively.Fatty acids in triglycerides(TG)had little change during 0-10 days,and linoleic acid oxidation was dominant during 10-30 days.Through the analysis of the fatty acids in the monoglyceride at the position of Sn-2 obtained by the enzymatic hydrolysis of triglyceride by pancreatic lipase,it was found that the main fatty acid of Sn-2 was oleic acid,linoleic acid decreased the fastest in the oxidation process.The linoleic acid at the position of Sn-1(3)was the main fatty acid,followed by oleic acid.The content of linoleic acid decreased to 54.57%,40.35% and 42.45% times,respectively.(4)The HS-SPME-GC-MS was used to analyze the volatile components at 0,10,20 and 30 days of the accelerated oxidation process of SAO.It was found that the olefines were greatly reduced at the 10 th day of the oxidation process of SAO,and all monoterpenes could not be detected at the 20 th day.The contents of trans-anethole and estragole decreased slightly at 0-20 days,but decreased sharply at 20-30 days.At 30 days,a large number of acid substances were formed,and the oxidized oil presented a pungent rancidity.During the accelerated oxidation process,the aldehydes kept rising,and heptanal,trans-2-hexenal,nonanal were generated at the beginning of 10 days,and the content of these substances gradually increased with the oxidation.At the 30 th day,trans-2-octenal was the highest among the three oils,followed by 2,4-decadienal,n-hexanal,trans-2,4-decadienal and nonal.Through the changes of volatile substance content and fatty acid content,it can be concluded that 3-nonene-2-one,n-pentanol and1-octene-3-ol are the degradation products of unsaturated fatty acid hydroperoxides,and trans-2-octenal is the product of linoleic acid hydroperoxides.The oxidation degree of star anise seed oil is best reflected by aldehydes.trans-2-Hexenal,trans-2-octenal,2,4-decadiene can be used as the evaluation index of the oxidation degree of the three oil samples. |
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