Fluorescence fingerprints of Sidr honey in comparison with uni/polyfloral honey samples

Abstract

Sidr honey from Ziziphus species is gaining importance after Manuka honey due to its health benefits, therefore chemical fingerprinting of the Sidr honey from different regions of Pakistan was performed in comparison with other unifloral (Elettaria cardamomum, Citrus reticulata and Grewia asiatica) and polyfloral honey. Front face, synchronous fluorescence spectroscopy (SFS) was recorded at an excitation wavelength range from 250–450 nm with offset of 60 nm. All honey samples have fluorescent emission peaks at 342 and 349 nm attributed to amino acid (Tryptophan). The emission spectra of raw Sidr honey showed clear discrimination from uni/polyfloral and commercial samples owing to its phenolic profile with peaks at 396 and major distinctive peak at 451 nm that corresponds to caffeic acid, chlorogenic acid and ferulic acid. Whereas a year old Sidr honey showed decreased and shifted fluorescence emission from amino acid and phenolic compounds respectively. Variation in fluorescent intensity of phenolic compounds in Sidr honey from different regions of Pakistan may be attributed to diverse species of Ziziphus in these geographical areas. A broad band from 395 to 459 nm in commercial honey samples are due to fluorescence of Maillard reaction products that could be generated during thermal processing of honey. Natural variability exists among honey samples owing to different floral origin as authenticated by Principal Component and Heirarchial Cluster Analysis techniques applied in this study. The unique fluorescence emission spectra of raw Sidr honey samples proposed front face SFS as a simple technique for the quick identification of its monofloral origin. Therefore, fluorescent inherent markers are helpful in identifying botanical and geographical origin and may also be standardized to authenticate the purity of honey.