Detection Of Volatiles In Honey And Identification Of Acacia Honey Adulteration By Mass Spectrometry

As a gift of nature,honey is widely favored by consumers because of its high nutritional value.The quality and price of honey are closely related to its plant source.As a result,the high value of some plant-source honey stimulates the adulteration of honey,which seriously harms the interests of consumers and the order of the honey market.In order to clarify the characteristic chemical components of honey from different plant sources and to explore the rapid identification method of acacia honey mixed with rape honey,we used static headspace-gas chromatography-mass spectrometry(SHS-GC-MS)and neutral desorption-extractive electrospray ionization-mass spectrometry(ND-EESI-MS)to obtain sample fingerprint information of the chaste honey,linden honey,rape honey,acacia honey and adulterated acacia honey with different concentrations of rape honey.Combined with multiple statistical methods of principal component analysis(PCA)and cluster analysis(CA),the chemical compositions of honey were obtained and evaluation models were established for honey source identification and adulteration detection.The main findings are as follows:1.To explore volatile markers in honey from different sources and to distinguish them effectively,38 samples of four common types of honey including rape honey,linden honey,chaste honey and acacia honey were used as experimental materials,and a SHS-GC-MS method was optimized for detecting and the volatile components.The samples were analyzed and distinguished by this optimized method combined with PCA and CA.The results showed that a total of 23 compounds were detected by SHS-GC-MS.The volatile components of the four kinds of honey samples had significant differences in types or contents,among them,Benzenepropanoic acid,ethyl ester were the typical metabolic substance of rape honey,Benzene,1-methyl-3-(1-methylethenyl)-and trans-Rose oxide are the typical metabolic substances of linden honey,and the typical metabolites are not found in the chaste honey and acacia honey.Four kinds of honey can be distinguished well by PCA,and the accumulative contribution rate of PC1,PC2 and PC3 reaches 77.3%,indicating that themodel is effective.When the critical value was taken as 10,the honey samples from same source can be well clustered by CA.Therefore,SHS-GC-MS combined with chemometrics can be used to distinguish honey of different sources.2.In order to establish a rapid identification method of acacia honey mixed with rape honey based on direct mass spectrometry,adulterated acacia honey mixed with different concentrations of rape honey was used as the experimental materials in this study.Firstly,a fast ND-EESI-MS analysis method was optimized for systematical study of honey without sample pretreatment.The results showed that the phenolic compounds in honey have higher signal response intensity and abundant material information under the negative ion mode.A total of 16 compounds,including 13phenolic compounds and 3 amino acids,were detected from rape honey under the positive and negative ion modes and tryptophan was detected only in rape honey.17compounds were detected in acacia honey,including 15 phenolic compounds and 2amino acids.Phenylacetic acid and chrysin were only detected in acacia honey.Rape honey,acacia honey and adulterated honey can be well distinguished using chemometrics.PCA established an effective discrimination model,and the cumulative contribution rate of PC1,PC2 and PC3 reached 99.3%.When the critical value was 7,CA could identify adulterated acacia honey with 10%rape honey.In partial least squares discriminant analysis,R~2 is 65.3%and Q~2 is 95.3%,which are higher than 50%,indicating that the model has good prediction ability and accuracy.The classification accuracy of discriminant analysis reached 100%.Heat map indicated that the material signal intensity of acacia honey decreased with the increase of adulteration concentration,while the material signal intensity of rape honey was opposite.Therefore,ND-EESI-MS is expected to be used for rapid detection of honey.Based on two kinds of mass spectrometry techniques,this study established the identification model of honey from different sources and the discrimination model of adulteration of rape honey mixed into acacia honey and the results provided theoretical and practical bases for the identification,adulteration and quality evaluation of honey.