Study On Free And Bound Aroma Components Of Five Natural Products In Wuling Area

Free and bound compounds exist in the flavoring ingredients of natural vegetable foods.In this thesis,a series of experiments were carried out by using different analytical methods for the flavor components of five natural products.And qualitative analysis,quantitative analysis and flavor profile analysis were performed on Litsea mollis Hemsl.,Hawk tea and of three different types of fruits.From the research above,the study shows:1.By response surface methodology(RSM),this part used the Box-Behnken design(BBD)to measure the content of ?-Citral and ?-Citral in the aroma component of Litsea mollis Hemsl..The study optimized experimental parameters,which include desorption time,salt addition,type of stationary phase of the SPME fiber,extraction time,equilibration time and equilibrium temperature.According to the Design-except test,the optimal conditions are 46 ?,36 min equilibrium time and 20 min adsorption time.2.This part aimed to determine the volatile components of Wuling area Hawk tea by headspace solid-phase microextraction and needle trap,coupled to gas chromatography-mass spectrometry(GC-MS).The results indicated that 49 volatile compounds were identified in the Hawk tea.The results showed that the main free volatile compounds were bornyl acetate,cadinol,?-eudesmol,and the bound volatile compounds were ?-eudesmol,?-selinene,guaiene.Based on the odor characteristics of those identified compounds,it can be concluded that the free odor of Hawk tea is mainly from decanal,dodecanal,bornyl acetate,spathulenol,and the bound odor were?-damascenone,spathulenol,linalool.3.By analyzing the changes of free and bound compounds during the storage of Turnjujube fruit,flavor compounds,volatile characteristics,and odor characteristics are closely related with storage time,and the contents of free alcohol,aldehyde,ketone,isobutyric acid,terpene and phenol are increased with the storage time of the fruit,while the contents of free ester and mesitylene are decreased which however remain high level.In addition the bound alcohols are the most important compound,and its content gradually decreases and then increases with the increase of storage time.1-Hexanol,hexanal and ethyl isobutyrate contribute to the main free flavor of the Turnjujube.The borneol,?-Damascone and eugenol are the main contributing compounds of the Turnjujube bound flavor.4.The free and bound aroma compounds during maturation of Rubus corchorifolius L.f.fruit was studied.The volatile profiles and odor characteristics changed significantly with its skin color changing from green,to yellow and red.The total content of free aldehydes,2-heptanone,alcohols,esters and phenols increased,while that of free terpenoids and norisoprenoids decreased,but remained at high levels,with the ripening of the fruit.The total content of bound aldehydes,alcohols,terpenoids and norisoprenoids,esters and phenols gradually decreased during ripening due to their hydrolyses to the free form.The free aroma compounds in red and yellow fruits exhibited similar odor profiles,and both of them were much sweeter,more floral and greener than green fruits with less bad odor.The free ?-damascenone,hexanal and 2-hexenal accounted for most of the odors of the relatively ripened yellow and fully ripened red fruits.The bound aroma compounds in red and yellow fruits were hydrolyzed to release enhanced floral,fruity and sweet odors without increasing bad odors.The formation mechanisms of some volatile compounds were proposed.5.This part was to investigate the free and bound volatile compounds in the Rubus coreanus(RC)fruits of different ripening stages.The contents of free(E)-2-hexen-1-ol,1-hexanol,2-heptanol,?-myrcene,(E),(Z)-?-ocimene,?-ocimene,linalool,cosmene,?-terpineol,methyl salicylate,eugenol and ?-damascenone remained high,and increased with during the whole ripening process.The contents of11 bound volatile compounds decreased during the ripening,and became lower than the contents of their free volatile compounds in the ripe fruit.The principal component analysis suggests that nonanal,sulcatone,(E)-2-hexen-1-ol,1-hexanol,2-heptanol,1-heptanol,1-nonanol,(E)-linalool oxide(furanoid)and ?-damascenone are the characteristic free volatile compounds of ripe RC fruit,and(E)-2-hexen-1-ol and(E)-?-ocimene were its characteristic bound volatile compounds.In addition,the ripe fruit was fruity and floral.The gradually released bound volatile compounds can enhance the fruity,floral and herbaceous odors.