Construction Of Volatile Compounds Thermal Response Characteristics And Identification Models Of Agarwood

Agarwood is a natural mixture of woody tissues and their secretions,which are formed during the growth of the species of the genus Aquilaria spp.Agarwood is known as the best incense,and the price is affected by the origin place.It is easy for non professionals to confuse the information of the growing area,and it is also difficult to distinguish between Qi-nan and normal agarwood.In this study,agarwood samples and the woods(Aquilaria spp.)were used as experimental materials.Studies were started from the perspective of agarwood aroma and the woods anatomy.The specific method is that the anatomical characteristics of 6 species of agarwood were compared.Agarwood samples were heat treated through TD-GCMS test,and the data was analyzed with chemometrics,and the woods were dissected and observed.Finally,the response characteristics of Volatile Compounds to different heating temperatures were discussed,3 discriminant models for the classification were established,4 species fingerprints were obtained.Through the work above,a basis for the identification of unknowns was provided.The main conclusions are as follows:(1)A clear consistency in the anatomical characteristics was showed in 6 wood samples,which mainly expressed as wood color,pore morphology,radiation pattern and abundant island type containing phloem.At the same time,there are certain differences,which were manifested in the gum and the wood fiber partition.Compared with Qi-nan(Aquilaria sinensis)and normal agarwood(Aquilaria sinensis),some differences were found.Qi-nan's containing phloem was about 436 per square centimeter,with slightly higher radiation of 2-28 ray cells,tangential crystals were found.While normal agarwood's containing phloem was about 176 per square centimeter,and its radiation was 2-15 cells high,and no crystal was observed.The differences of Hui-an(Aquilaria crassna)and Sin-chow agarwood(Aquilaria filaria)were shown in the following point.In Hui-an sample the phloem containing is slightly higher with 774-967?m,and no gum and septate fiber was observed.In Sin-chow sample,the phloem containing is 774-967?m high,and the gum was rich,and wood fiber partition can be seen.(2)The main heat treatment products of Qi-nan and normal agarwood are sesquiterpene and the other aromatic compounds.The total relative peak area of sesquiterpene in Qi-nan sample was 46.2-70.0%,and that of other aromatic compounds was 3.3-11.1%.The total relative peak area of sesquiterpene in normal agarwood was 48.7-64.6%,and that of other aromatic compounds was 8.7-15.0%.The higher heat treatment temperature,the more sesquiterpene and the other aromatic compounds get in samples in both Qi-nan and normal agarwood.The relative intensities of sesquiterpenes were higher than that of other aromatic compounds in both of the two samples.The highest total relative peak area of Qi-nan sample became when 120?.The components with molecular weights of 134.073,136.052,148.052,178.099,218.167 be detected in Qi-nan sample only when the temperature is no less than 160?.The highest total relative peak area of normal agarwood sample came out when 140?.(3)The method that agarwood samples heat treatment combined with TD-GCMS test and chemometrics analysis can be used in the following three discriminant models,that were Hui-an and Sin-chow discriminant model,Qi-nan and normal agarwood discriminant model,and Qi-nan,Hui-an and Sin-chow discriminant model.In this process,the stepwise regression model was used to screen the independent variables as characteristic compounds which can effectively simplify the model calculation.Fisher discriminant analysis and Bayes discriminant analysis were used to distinguish agarwood samples seriously.The initial validation rates of the three models were 100%,and the accuracies of cross validation were greater than 97%.The discriminant formulas(and the center of gravity in FDA)derived from the discriminant models can be used to identify the incense samples of unknown categories.(4)4 fingerprints were established,that were Qi-nan from Vietnam,agarwood from Hainan,agarwood from Vietnam,and agarwood from Indonesia.RSD of relative retention time and that of relative peak areas of common peaks were less than 5%,indicating the sample peaks were very well aligned,and the total peak strength showed regularity in some distance.The fingerprints of the samples were consistent with the comparison results of the anatomical characteristics.