Study On The Detection Method Of Aroma And Flavor Substances In Fragrant Rice Based On Thin Film Microextraction

Aromatic rice(Oryza sativa L),which is a special typle of rice with a long cultivation history and is known for its long cultivation history and rich aroma.Aroma and flavor substances are one of the im-portant factors affecting the aroma type and quality of fragrant rice.However,current methods for de-tecting the aromatic compounds in rice are limited in their ability to effectively extract low concentration and total components,which hinders improvement in rice quality.The study focuses on developing a detection method for aroma and flavor substances in fragrant rice and reveals the correlation between aroma and flavor substances and rice fragrance types.The study uses thin film microextraction technology combined with thermal desorption equipment and gas chromatography-time-of-flight mass spectrometry for analysis and identification of aromatic compounds.The NIST library,retention index-aided qualitative method,and internal standard method are used for quantification.The study also uses odor activity value(OAV)to construct a correlation system between aromatic compounds and rice fragrance characteristics and identifies important flavor compounds to determine the aromatic flavor type of the tested rice variety.The test results are as follows:(1)Thin film microextraction method(TFME)optimized conditions include a DVB/PDMS coating for extraction,a 90-minute extraction time,an extraction temperature of 80℃,a TDU heating rate of 60℃/min,and an initial CIS temperature of-20℃.Compared with the control group,the volatile compounds extracted by the TFME method are 2.1 times the solid-phase microextraction(SPME)method,and the key com-pounds detected are three times that of the SPME method.(2)There are significant differences in the quantity and concentration of aroma compounds among different aromatic rice varieties.Among the compared varieties,Longjing 3155 has the highest total concentration of aroma compounds,while Erxiaoxiang Q02 has the largest number of detected com-pounds.By comparing the different types of compounds among the varieties,it was found that the highest content is alcohol compounds,accounting for 31% to 55% of all aroma substances in the varieties.Al-dehydes have the largest number of compounds among all categories.(3)Among the 14 fragrant rice varieties tested,13 key flavor substances were detected in all vari-eties of fragrant rice,which are considered to be commonly shared key flavor substances in aromatic rice.They are 2-acetyl-1-pyrroline,lauric acid,1-octen-3-ol,indole,octanal,heptanal,2-pentylfuran,1-octanol,decanal,hexanal,dibutyl phthalate,diacetyl,and(E)-2-octenal.Ten key flavor substances were detected in some varieties,which are considered to be unique aroma substances for some varieties and provide unique aromatic flavors for aromatic rice varieties.They are γ-nonalactone,nonanal,2-methoxy-4-vinylphenol,β-ionone,(E,E)-2,4-decadienal,guaiacol,phenylactaldehyde,1-decanol,1-heptanol,and(E)-2-octenal.Fragrant rice varieties classification were conducted according to OAV values and aroma descrip-tions.Among them,Longjing 1525 has violet flavor.Erxia Xiang Q02 and Longqingdao 36 has coconut flavor.Longjing 3155,Longjingxiang 1,Erxia Xiang Q07,Longqingdao 99 has Smoky flavor.Longjing 4801,Erxia Xiang Q02,Erxia Xiang Q08,Longqingdao 36 has cheesy and slightly medicinal aroma flavor.Erxia Xiang Q02,Erxia Xiang Q07,Longqingdao 99,Longqingdao 8 has musk flavor.Longjing 1525,Longjing 3155 has Grass flavor.Erxia Xiang Q08,Hajaponicadao.8,Hajaponicadao.10,Hajaponicadao.11,Longqingdao 36 and Longqingdao 99 has orange flavor.