Βotanical Origin Confirmation and Adulteration Testing of Monofloral Honey Using ATR-FTIR Spectroscopy in Combination with Pattern Recognition and Dimension Reduction Techniques.

The present study aimed to investigate whether Attenuated Total Reflectance-Fourier Transform Infrared (ATR-FTIR) spectroscopy could be effectively applied for the botanical origin confirmation of monofloral (fir, thyme, pine) and flower/polyfloral (flower, citrus, asfaka, and mixtures) honey in accordance with melissopalynological analysis, and to unveil the adulteration of monofloral honey with flower/polyfloral honey. Fifty-nine samples were subjected first to melissopalynological analysis to record the dominant pollen flora. Afterwards, ATR-FTIR analysis identified the dominant spectral regions of interest. Among them, 3300-3200 cm-1, 2970-2920 cm-1, 1730-1600 cm-1, 1420-1410 cm-1, 1390-1380 cm-1, 1380-1330 cm-1, 1260-1225 cm-1, 1210-1180 cm-1, 1150-1130 cm-1, 1100-1010 cm-1, and 950-750 cm-1 showed a differentiation potential. Pattern recognition [multivariate analysis of variance (MANOVA)/linear discriminant analysis (LDA) and dimension reduction (factor analysis)] techniques resulted in 100% classification of samples by botanical origin, with the most significant factor parameters being the regions of 1730-1600 cm-1, 1420-1410 cm-1, and 950-750 cm-1, which indicate the presence of water, carbohydrates, ketones, amino acids, and organic acids. Fir, thyme, and pine samples were also adulterated with the batch of flower/polyfloral honey samples (20% w/w), and ATR-FTIR, in combination with the aforementioned multivariate techniques, differentiated the adulterated samples from monofloral samples with an overall cross-validation prediction rate of 91.2% based on LDA. ATR-FTIR, when combined with chemometrics, can be a rapid analytical technique for confirming the botanical origin and adulteration of monofloral honey with polyfloral honey, with an error rate below 9%.