Effect Of Roasting Sunflower Seeds On Flavor And Quality Of Sunflower Oil

Flavored sunflower oil (FSFO) which meets domestic consumers’ special expection onsensuous comforts of oil has great market prospect. Flavor is a critical quality index to FSFO,and its formation is significantly linked to heating process of sunflower seeds when producingFSFO. Therefore, the study on flavor composition and its origin in SFO and effect of roastingprocess on SFO quality will help to make better understanding of SFO flavor,so that to makebetter control and improvement in FSFO production. The main contents of this dissertationbrief as follows.Firstly, method of HS-SPME-GCMS for detecting volatile compounds in the headspaceof SFO was determined.ptimization HS-SPME condition was chosen and at50oC extractiontemperature,50min extraction time and5min desorption time. Finally,95kinds of volatilecompounds were identified in the headspace of oil sample, which accounted for83.14percentof total volatile compounds.Secondly, characteristic SFO flavor was indentified by GC-O with time-intensity method,which contains grilled flavor, herbal aroma and the oily smell. It was found that the roastedand grilled flavor were mainly from compounds like methylpyrazine,2,5-dimethylpyrazine,2,6-dimethylpyrazine,2-ethyl-5-methylpyrazine,3-ethyl-2,5-dimethylpyrazine,2-ethyl-3,5-dimethylpyrazine,while hexanal,2-hexene, α-pinene,2-pentylfuran, phenethanoland2-acetylpyrrole contributed for the herbal and light flower aroma. In addition, verbenoland2,3-dihydrobenzofuran expressed the sweetness, and octenal showed the oily smell.Thirdly, sunflower seeds were roasted at different temperatures and times before beingpressed to produce sunflower oil. Then, Oil samples were systematically analysed by sensoryevaluation, electronic nose (EN) and HS-SPME-GCMS. Samples which were pretreated at140oC for30min or150oC for20min achieved higher scores by sensory evaluatoin.Insufficient roasting brought more sweetness than grilled flavor whereas overroasting broughtbrunt smell, both of which did not give off pleasant characterisic flavor of SFO. EN resultsshowed quite good ability to tell different flavor quality SFO apart. A total of83kinds ofcompounds were found in the oil samples produced in different roasting conditions by GCMS.There were23N-heterocyclic compounds, including18pyrazines,2pyridines and3pyrrolrs,19O-heterocyclic compounds, including8furans, other nonheterocyclic compounds mainlyincluding11aldehydes and7alkenes. Among kinds of compounds mentioned above,pyrazines ranked the top from perspective of type and percentage, which meant it dedicatedmost to the characteristic flavor of sunflower oil. Flavor precursors were indentified as Lys,Arg and His through comparing content of amino acid before and after roasting and aminoacis-gulcose-oil model.Finally, analysises were conducted to determine the quality of roasted-pressed sunfloweroil. Results showed that SFO in diffenent roasted conditions is of high quality, which metgovernment’s standards on AV and PV and contained over80%unsasturated fatty acid. Withhigher roasting temperature and longer roasting time, color of oil samples deepened andcontent of VE depressed slightly, indexes, including compositions of FA and sterols changed smoothly with different roasting conditions. Furthermore, stepwise regression analysismethod showed that content of VE could be predicted by AV and PV through linear relation.