High-Throughput Monitoring Of Multiclass Syrup Adulterants In Honey And Identify The Botanic Source Based On MALDI Mass Spectrometry

Honey is a natural sweetening agent produced by bees from flower nectar or honeydew,which should be free from any exogenous substance or food additive.In recent years,the demand for honey has increased because of its nutritional value,therapeutic effect and unique flavor,which leads to the increasing honey adulteration.In addition,there are also the phenomenon of shoddy goods for quality goods,such as multifloral honey as unifloral honey,and immature honey as mature honey.The existing analysis methods have some limitations such as long analysis time or complex sample pretreatment.Therefore,effective analysis and detection methods for the honey authentication are still highly desirable to ensure its quality and safety.In the present study,matrix-assisted laser desorption/ionization mass spectrometry(MALDI-MS)was applied for the detection of saccharides and small molecule metabolites of honeys and adulterated ones.The method is effective and robust for the high-throughput monitoring of honey adulteration and botanic source,and provides a new perspective for the identification of other high-carbohydrate foods.The main research contents and results are as follows:1.Honeys,syrups and 10%adulterated honeys were detected by MALDI-MS using 2,5-DHB as matrix.Oligo-and polysaccharides were observed as alkali ion adducts[M+Na]+and[M+K]+in positive mode,and the qualitative analysis of saccharides in the samples were achieved according to the spectral characteristics of[M+Na]+and[M+K]+.By comparing the distribution of saccharides of honey samples to adulterated ones,adulteration at the 10%level in honey produced a significant increase of the oligosaccharides of DP 6 and DP 7 and broken the trend that signal strength decreases with the increasing DP.Meanwhile,polysaccharides(DP? 13),which were not present in honeys,were found in the adulterated samples with 10%CS.The ratio of DP 6:DP 5(or DP 7:DP 6)was less than 1 in honey samples but more than 1 in adulterated ones,which could be used as markers for the identification of adulteration with starch syrup(HFCS and CS).And the MS-based strategy also allowed revelation of the presence of polysaccharides(DP?13)coming from CS that could be used as an indicator for its identification of adulteration,even with just 10%addition.2.Here we applied NEDC as a novel matrix to detect oligosaccharides,and the composition of oligosaccharides isomers was firstly used for the high-throughput monitoring of honey adulteration with CS or IS.In negative mode,structural information of oligosaccharides was analysed by MALDI-LIFT-TOF/TOF with their[M+Cl]-precursor ions,in which di-,tri-and tetrasaccharides could present different fragment patterns in honey and adulterated honey samples thereby realizing the distinction between them.The relative peak intensity(RPI)of product ion pairs represents the relative content of oligosaccharide isomers.The MS/MS spectra of di-,tri-and tetrasaccharides were compared between authentic honey samples and adulterated ones.The addition of 10%CS or IS changed the oligosaccharide composition of honey significantly,manifested as the variation of the RPI of characteristic fragments between honey and adulterated honey.And some diagnostic product ion pairs could be used as markers for the identification of adulteration with CS,including the ratio of m/z 281:341 from m/z 377.1,m/z 161:179 and m/z 341:383 from m/z 539.1,m/z 161:179 from m/z 701.2.And the ratio of m/z 251:341 from m/z 377.1 could be used as a marker for the identification of IS-adulteration.3.The fingerprints of three honeys(acacia honey,chaste honey and jujube honey)were obtained by MALDI-TOF-MS,and three honeys were rapidly differentiated by multivariate analysis(PCA,PLS-DA and OPLS-DA).h-BN,2,5-DHB and NEDC were used to characterize the honey samples,then NEDC was used for the detection of samples in negative mode.From the mass spectra of the three honeys,m/z 215,m/z 377,m/z 539 and m/z 701 could be observed,which could be identified as[M+Cl]-of monosaccharides,disaccharides,trisaccharides and tetrasaccharides by tandem mass spectrometry and high resolution mass spectrometry.PCA showed that PC1,PC2,and PC3 have a total contribution rate of 80.9%.Then PLS-DA and OPLS-DA model also was established to distinguish three honeys effectively.