Study On The Determination Of Volatile Compounds In Oilseeds And Oils Based On GC×GC/TOF MS

The vegetable oils are the essential consumer products in daily life. With the development ofpeople’s living standard, the requirement of high quality plant oils is increasing. The flavor, which is thecrucial aspects related to the quality of edible oils, is the major factor to identify different oils. And thevolatile compounds are the major factor of affecting the flavor of oils. The value of plant oils in Chinadepends on the species, flavor and nutrition compounds. However, there are few research reports aboutthe volatile compounds in the vegetable oils. In order to guarantee consumers’ right and health and thevegetable oil quality evaluation via establishing the fingerprint database of the volatile compounds inoilseeds and oils, it is important to research the method of extraction and detection of chemicalcomposition and the flavor diversity.Under optimized parameters of extraction, chromatogram condition and mass spectrum, thevolatile compounds of rapeseeds, peanuts and soybeans were confirmed by improved solvent-freemicrowave extraction-comprehensive two-dimensional gas chromatography/time-of-flight massspectrometry (ISFME-GC×GC/TOF MS). The three-dimensional fingerprint spectrograms wereestablished. By the comparison of improved solvent-free microwave extraction (ISFME) andconventional solvent-free microwave extraction (CSFME), the composition and content of theircharacteristic volatile compouds in oil seeds were identified. Based on optimized conditions ofhead-space extraction, chromatogram condition and mass spectrum, head space coupled withcomprehensive two-dimensional gas chromatography time-of-flight mass spectrometry(HS-GC×GC/TOF MS) was applied to determine the volatile compounds of cold pressing vegetable oils.The three-dimensional fingerprint database of the volatile compounds including20cold pressing plantoils were collected. Compared with the results, the volatile symbols related to the particular flavorsbetween oil samples were identified.1.Improved solvent-free microwave extraction-comprehensive two-dimensional gaschromatography/time-of-flight mass spectrometry was applied to analyse the volatile compounds fromrapeseeds, peanuts and soybeans. Volatile compouds were extracted by adding carbonyl iron powders(CIP) into oilseeds in order to accelerate extraction without solvent. And the ratio of CIP to sample was1:5via the optimization of extraction. The optimized conditions of GC×GC/TOF MS were set asfollows: column system: DB-5MS column (1D) coupled with DB-17ht column (2D); modulation period:4s; initial oven temperature:35℃. And the separation achieved the maximization. Compared theISFME and CSFME by GC×GC/TOF MS, it was observed that the ISFME made the whole processmore simple, economoical and time-saving than CSFME method. Volatile components extracted inCSFME and ISFME were consistent. Most of heterocyclic compounds, oxidation volatiles (alcohol,aldehyde, ketone, hydrocarbon and acid ester), sulfur compounds, nitrogen compounds and benzenerings were identified in which heterocyclic compounds were the main volatiles. The contents ofoxidation volatiles extracted by ISFME were higher, which produced more flavor compositions.2. Determination method for volatiles in cold pressing plant oils was established by the application of head space coupled with comprehensive two-dimensional gas chromatography time-of-flight massspectrometry. The optimized parameters were as follows: sample quality:2.0g; heating time for headspace (HS):30min; jolting shake:500rpm; injection volume:0.5mL; column system: DB-5MS column(1D) coupled with DB-17ht column (2D); modulation period:4s; initial oven temperature:35℃.HS-GC×GC/TOF MS was applied to the determination of the volatile compounds in rapeseed oils,peanut oils and soybean oils. The three-dimensional fingerprint spectrograms were established. Manyoxidation volatiles and heterocyclic compounds which including particular flavors wereidentified.3. The volatile compounds of20cold pressing plant oils were identified employing HS-GC×GC/TOF MS.18common volatiles among the oils which including aldehyde (C4-C9), ketone,hydrocarbon and heterocyclic compounds (Furan,2-pentyl-) were confirmed. The particular flavorcompouds from grape seed oil, coconut oil, sunflower oil, perilla oil, olive oil, sesame oil, sea buckthornoil, rapeseed oil, peanut oil, tea seed oil, castor oil, cottonseed oil, wheat germ oil, safflower oil, linseedoil, soybean oil were took acount of15,8,7,14,12,4,5,6,6,4,6,12,4,2,2,1.Volatiles including aldehydes, alcohols, ketones, heterocyclic compounds, hydrocarbons and acidesters were identified differently in20oil samples. Such as sesame oil, sunflower oil, peanut oil,safflower oil, tea seed oil, corn oil, olive oil, castor oil, palm oil, grape seed oil, sea buckthorn oil, ricebran oil, cottonseed oil, the contents of aldehydes were the hightest for13vegetable oils. And thecontent of aldehydes in palm oils was46.04%. The contents of alcohols were the hightest for rapeseedoils, soybean oils, walnut oils, linseed oils, perilla oils, wheat germ oils. Especially for linseed oils andperilla oils, the contents were52.57%and51.75%. The content of acid esters was the hightest forcoconut oils, and it was31.95%. Taking the relative contents of six kinds of volatiles as variables, theprincipal components analysis plots of20cold pressing plant oils were figured.20vegetable oil sampleswas differentiable visually from the plot.