Use of physicochemical, FTIR and chemometric analysis for quality assessment of selected monofloral honeys

The aim of this study was to assess the quality and characterise a selection of honey varieties with the use of physicochemical, FTIR, and chemometric analysis. The research material consisted of monofloral nectar honeys of 5 distinct varieties: black locust, raspberry, oilseed rape, linden, and buckwheat. The contents of water, soluble solids, 5-hydroxymethylfurfural, free acidity, pH, electrical conductivity, and water activity were measured. Infrared spectra were measured within the spectra range from 3700 to 780 cm(-1). The obtained results from the FTIR measurements for selected honeys showed the greatest changes in the area of the band maxima: 3333, 1641, 1453, 1248, 1184, 1033, and 985 cm(-1). The identification of the origin and chemometric analyses were provided for the spectral regions with the maxima at approximately 3333 and 1641 cm(-1) (vibrations from water fractions), 2935 and 2885 cm(-1) (symmetrical and asymmetrical vibrations of the -CH2 and -CH3 groups), as well as the fingerprint region where varying intensities of the characteristic bands were observed. Chemometric analysis of the FTIR spectra confirmed the high quality of the analysed honey varieties as well as the differences also in their sugar fractions. The results obtained after employing PCA in the spectroscopic analysis of infrared spectra evidence high applicability of the methods of multi-dimensional statistical analysis in the determination of discrepancies, similarities, and structural characteristics of any given type of honey. A catalogue of FTIR spectra can be created to allow fast and cost-effective identification of honeys, compared to traditional methods.