Study On Changes Of Quality And Aroma Components Of Rapeseed Oil During Refining And Storage

With the development of consumer demand for the aroma of rapeseed oil,this topic provides a theoretical basis for processing and producing rapeseed oil with a unique fragrance through the study of the change law of aroma components during the process of rapeseed oil refining and storage.Using Gas Chromatography-Mass Spectrometry(GC-MS)combine with Electronic nose(E-nose)technology is used to explore the changes in key aroma components of rapeseed oil during refining,different producing areas,and storage processes.The conclusions are as follows:(1)The Acid Value(AV)and Peroxide Value(POV)were reduced after refining the leached crude oil and small pressed crude oil.Among them,the components that contribute to the key aroma were glucosinolate degradation products,aldehydes,and pyrazines.The relative content of glucosinolate degradation products was the highest in the deacidification section,and the relative content was reduced in the small squeezed fourth-grade oil.The relative content of glucosinolate degradation products after refining small pressed crude oil was reduced.Pyrazine compounds weren't detected in the deodorized oil,and the relatively low content of the small squeezed fourth-grade oil was 3.45%.Aldehyde compounds reached the highest level in decolorized oil,and decreased sharply after passing through the deodorization section;the relative content of aldehyde compounds increased from 5.08% to12.98% after the refining of small pressed crude oil.The aroma components of the extracted crude oil change greatly during the decolorization and deodorization process,and the aroma components of the small-squeezed crude oil had little change.Therefore,the two processes of leaching crude oil refining and controlling the decolorization and deodorization could reduce the loss of aroma.The small-squeezed fourth-grade oil was better than deodorizing The aroma components of oil were more complex,so the aroma was better.(2)Flavor profiles of virgin rapeseed oils(VROs)are comparatively studied for trend of change of various flavor types.The ROAVs of key odorants detected by GC-MS data were visualized to discriminate VROs with various flavors by using PCA to determine the main volatile components.Based on GEI the aroma of VROs of different place of production was evaluated.Results showed that 14 key odorants comprising aldehydes,glucosinolate degradation products and pyrazines were identified based on their ROAVs.3-ethyl-2,5-methylpyrazine,nonanal,2,4-decadienal,methallyl cyanide,phenylacetaldehyde,lauric aldehyde,etc.were the main volatile compounds in the VRO from different places.The aroma of VROs were significantly different.Under the conditions of this experiment,the results of the GEI evaluation showed that the best aroma quality of the 10 producing areas of rapeseed oil was in Chengdu.The volatile composition of the VROs from different places had certain similarities and also large differences,and took on their own unique qualities and flavors.(3)Volatile flavor components of first-grade pressed rapeseed oil(S1)and fourth-grade pressed rapeseed oil(S2)stored at 60 ? were profiled by means of headspace solid-phase microextraction with gas chromatography-mass spectrometry(HS-SPME-GC-MS)coupled with E-nose technology,followed by correlation analysis quality indicators.The results showed that the acid value of S1 and S2 was related to acid compounds.The content of aldehyde compounds had an important correlation with the degree of oxidation deterioration.The peroxide value of S1 was generally higher than that of S2.After 20 d of storage,S1 was higher anisidine value(PV)than S2.S1 had a high oxidation rate in the early stage of oxidation,and S2 had a high oxidation rate in the later stage of oxidation.It showed that the deterioration degree of S1 was higher than that of S2.The key aroma components of rapeseed oil during storage were mainly aldehyde compounds.The characteristic flavor components of S1 storage for 20 d were decanal,(E,E)-2,4-nonadienal and 2,4-decadienal.The characteristic flavor components of S2 store for 20 d were 2,4-decadienal and(E,E)-2,4-decadienal.The E-nose radar chart could distinguish the difference between the unreserved oil and the oil after storage,as well as the difference in aroma components in the early and late stages of storage.The content of(E)-2-decenal,(E)-2-nonenal,octanal and2-undecenal were related to the POV,AV and total oxidation value(TV)of S1.The content of nonanal,(E,E)-2-4 decenal,(E)-2-decenal,(E)-2-nonenal,decanal,octyl aldehyde and heptanal were related to the POV,PV and TV of S1.Volatile components could be used as indicators to monitor the oxidation degree of rapeseed oil during storage.(4)E-nose combined with PCA and LDA can more accurately distinguish the refining process and the overall changes in the aroma of rapeseed oil in different producing areas.