| China is the second largest importer of sesame seeds and their products,and the flavor of sesame products is an important factor influencing consumer acceptance,and its unique flavor formation is closely related to the heat treatment process.This paper explores the changes of sesame quality under different heat treatment conditions,and focuses on the effects of heat treatment conditions on the volatile substances and lipid composition of sesame,with the aim of providing a partial theoretical reference to elucidate the mechanisms of lipid involvement in flavor formation during heat treatment.The main studies are as follows:(1)Sesame seeds were used as raw material and heat-treated in oil bath,roasting and microwave at different intensities to observe the effects on the composition of sesame seeds and the antioxidant capacity of sesame meal.The results showed that the heat treatment process reduced the moisture content of sesame(from an initial 4.22%to 0.20%?2.18%)and increased the oil yield(from an initial 52.44% to52.65%?54.92%).Heat treatment did not significantly change the content of lipid concomitant gamma-tocopherol.However,the content of 5-HMF,an intermediate product of the Maillard reaction,showed a trend of increasing and then decreasing with the increase of heat treatment.Heat treatment was able to increase the content of sesamol and total phenols,while the flavonoid content showed a tendency to decrease and then increase with the increase of oil bath temperature.Oil bath and microwave treatments also increased the sesamin content to some extent,but the oven treatment had less effect.In addition,sesamolin content showed a trend of increasing and then decreasing with the increase of temperature and power.The 210 °C oil bath treated samples exhibited the strongest DPPH radical scavenging ability(31.31 ?mol/g),ABTS radical scavenging ability(204.00 ?mol/g)and FRAP ferric ion reducing ability(5.15 ?mol/g).Overall,heat treatment can change the composition of sesame oil(meal)and improve the antioxidant capacity of sesame meal.(2)The changes of the volatile components of sesame under different heat treatments were monitored by HS-SPME-GC/MS technique,and a total of 89 volatile components were detected.The heat treatment enriched the volatile species,among which the number of pyrazines,pyridines and other nitrogenous substances showed a significant upward trend,while the number of aldehydes and ketones showed a trend of increasing and then decreasing with the increase of heat treatment intensity.Cluster heat map analysis revealed that hydrocarbons such as alkanes,limonene and ?-ocimene and alcohols such as 1-pentanol had higher relative contents in raw sesame,130 °C oven,210 W and 350 W microwave-treated systems.The relative content of aldehydes such as hexanal,nonanal,benzaldehyde and benzeneacetaldehyde in the system increased significantly with the corresponding increase in the degree of heat treatment of the 130 °C oil bath,150 °C and 170 °C oven treatment systems.The relative contents of phenolic(2-methoxy-phenol,2-methoxy-4-vinylphenol and 1,3-benzodioxol-5-ol),pyrazine(methyl-pyrazine,2,5-dimethyl-pyrazine and 2,6-dimethyl-pyrazine,etc.)and furan compounds(furfural and 5-hydroxymethylfurfural)in the 190 °C and 210 °C oven,150 °C and 170 °C oil bath and 560 W microwave treatment systems were further increased,and the relative contents of aldehydes,alcohols and hydrocarbons were decreased.The relative contents of pyrazine,pyridine and other nitrogen-containing compounds were higher in the 700 W microwave,190 °C and 210 °C oil bath treatment systems.(3)Five methods,Folch(FT),Bligh-Dyer(BDT),Matyash(M),dichloromethane substituted Folch(FD)and Bligh-Dyer(BDD),were compared for the extraction of sesame lipids for a comprehensive analysis of sesame lipids.A total of 60 lipid compounds were identified,with 16 and 18 carbon atoms as the major fatty acid conformation,containing 7 DG and 39 TG,in addition to 3 LPC,9 PC and 2 PE.The five methods showed only small differences in the extraction ability of the identified lipids,but the M method has the advantage of being easier and relatively safer to operate,and is more suitable for lipid extraction from sesame.(4)The changes in lipid composition of sesame seeds obtained from oil bath treatments at 130,150,170,190 and 210 ? compared to raw sesame seeds were analyzed by M lipid extraction method combined with UPLC-Q-TOF/MS technique.The results showed a strong influence of temperature on lipid composition.Further screening of the differential compounds revealed that the differential compounds were dominated by phospholipids,and their abundance tended to increase and then decrease with increasing temperature,in addition,they had a strong correlation with volatile flavor substances such as nitrogen-containing heterocyclic compounds and aldehydes,which can be used as potential lipid components affecting the heat treatment flavor of sesame. |
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