Effect Of Roasting Process On Main Components Of Sesame Seed And Volatiles Of Sesame Oil

As a kind of natural flavor oils,sesame oil has not only high nutritional value but also special flavor,which is different from other vegetable oils.Roasting process has important effects on volatile components of sesame oil,due to different roasting degree;there are different color,quality characteristics and volatile components of sesame oils.The sesame seeds were roasted with a heated pan by conduction oil.The effects of roasting process on the quality of sesame oil extracted by aqueous extraction method,the content of amino acids(based on the relative contents of amino acids in defatted sesame meal)and the amount of soluble sugar in sesame seeds were determined.With the increasing of the roasting degree,the color of sesame oil became deeper and the peroxide value increased gradually;while the sesamin content was not changed obviously(between 0.84% and 1.02%),the amount of sesamolin decreased gradually(from 0.47% to 0.25%)and the content of the sesamol increased significantly(a maximum value of 0.01%);the total amount of trans-fatty acid in sesame oil increased gradually up to 0.87%.At 240 ?,with the prolonged roasting time the amount of soluble sugar decreased and the amino acid composition in defatted sesame meal have been changed that the relative content of serine,cystine*,lysine and arginine decreased obviously,which may be related to maillard reaction during roasting process,etc.The detecting condition of Headspace solid phase microextraction gas chromatography-mass spectrometry(HS-SPME-GC/MS)was optimized through the single factor experiment.The volatile components of sesame oil were detected under optimal condition: sample mass 3 g,extraction temperature 60 ?,extraction time 40 min,thermal desorption time 5 min,flow rate 1.0 m L/min.Sensory evaluation of sesame oil showed that the score of sesame oil roasted at 240 ? for 25 min was highest.Baked odor and anxious burnt flavor became strengther with the increasing of roasted degree,which became the main flavor characteristics of sesame oil gradually,replacing sweet taste and grassy.Electric nose was used to distinguish and analysis the overall flavor characteristics of sesame oil.The contours of sesame oils roasted at 220 ? and 230 ? have a lot of overlap,of which the flavor characteristics is similar;but far away from the sesame oils roasted at 240 ? and 250 ?,it showed that,high temperature roasting process have great impact on the volatile components of sesame oil,which make the flavor characteristics of sesame oils have significant difference.Headspace solid phase microextraction(HS-SPME)and GC/MS was combined to analysis the volatile flavor compounds in sesame oil.It show that,the main volatile components of raw sesame oil were aldehydes 18.16%,alcohols(1-hexanol)9.01% and hydrocarbons and epoxy hydrocarbons 57.09%;the relative amount of some compounds were increased with the prolonged roasting time such as pyrazines,pyrroles,furans and phenols,while the content of aldehydes,alcohols,hydrocarbons and epoxy hydrocarbons was decreased;in addition,the relative content of furans and pyrazines were all increased firstly and then decreased.Therefore,too roasting time is not appreciated.The flavor score model was builded to evaluate the flavor score of sesame oil.The schematic for the effect of roasting temperature and time on the score of sesame oil flavor showed that,sesame oil roasted at 240 ? for 25~30 min have the highest score,and roasting temperature have a far greater impact on flavor score than roasting time.