Fluorescence of bio-molecules a simple and quick method: What honey emission speaks about bee society and honey quality

Abstract

Fluorescence is non-destructive, sensitive, simple and fast method for analysis of fluorescent compounds contained in very low amounts (nanomolar concentrations) in the samples. It can be used for structural or concentration studies, in analytical or diagnostic purposes [1].The fluorescence spectra, in combination with appropriate statistical methods, may provide useful fingerprints in food analysis [2]. Various methods for study of honey quality and adulteration have been in research focus [3]. Over the last years, in different geographic areas a notable los of honey bee (Apis mellifera L.) colonies has been reported. A number of stressors affecting honey bees, including diseases, parasites, pesticides and poor nutrition have been identified [4]. Therefore fast and reliable methods are required for screening bee products both as a tool for assessing quality and to identify risks for colony state. We used fluorescence spectroscopy combined with advanced statistical analysis in order to identify variability in Fruska Gora lime tree (Tilia L.) honey collected at different locations in 2015. Since homogenization of the honey before packing in jars is considered as critical procedure from the Quality Control point of view, we have explored to what extent the ratio of the two main fluorophores in honey, originating from proteins and phenolic compounds change between extraction stage to packaging. Steady state fluorescence spectroscopy in combination with Multivariate Curve Resolution Alternating Least Squares (MCR-ALS) for spectral analysis has been applied to differentiate samples of honey. The three-dimensional excitation–emission matrix (EEM) is a rapid, selective and sensitive method: by changing excitation and the emission wavelength simultaneously, information regarding the fluorescence characteristics of the different compounds contained in the sample of interest can be obtained [5]. Proteins in honey mainly originate from bees and their quantity depends on bee society [6]. Phenolic compounds come from plant sources. In our study the source was the same – lime from close localties on Fruska Gora. As a control experiment we quantified proteins and phenols in the honey samples. Changed fluorophore ratio between extraction and packaging stage may indicate that analysed sample was not representative for the particular apiary, or honey homogenization was non-adequate before packaging. This reflects variation in properties of the bee colonies.The contribution of plant source to the honey emission spectra was estimated by comparing emission spectra of lime polen and honey. REFERENCES [1] B. Valeur, Molecular fluorescence: Principles and applications 63 (2001). [2] J. Sádecká , J. Tóthová, Czech, J. Food Sci. 25, 159-173 (2007). [3] K. Ruoff, W. Luginbuhl, R. Kunzli, S. Bogdanov, J. Oliver Bosset, K. von der Ohe, W. von der Ohe, R. Amadoa, J. Agric. Food Chem. 54, 6858−6866 (2006). [4] N. Even, J.M. Devaud, A. B. Barron, Insects3, 1271-1298 (2012). [5] B. B. Campos,D. Mutavdžić,M. Stanković,K. Radotić, M. Algarra et al., New J. Chem.41, 4835-4842 (2017). [6]H. Nazarian, R. Taghavizad, A. Majd, Pak. J. Bot. 42, 3221-3228 (2010).