Estimation of honey bee colony infection with Nosema ceranae and Varroa destructor using fluorescence spectroscopy in combination with differential scanning calorimetry of honey samples

In this preliminary study, we applied the Multivariate Curve Resolution- Alternating Least Squares (MCR-ALS) method to analyze the excitation-emission matrices of multifloral honey samples, combined with differential scanning calorimetry (DSC) to estimate infection of honey bee colonies with N. ceranae or V. destructor. Fluorescence spectroscopy combined with MCR-ALS was used to determine the ratio of the spectral components originating from proteins (C1) and phenolics (C2), two minor but essential constituents of honey, as a ratiometric indicator of infection level in related hives. The C1/C2 ratio decreased linearly with the increase of infection in both N. ceranae and V. destructor cases, the R2 was 0.941 and 0.912, respectively. Additionally, DSC has shown that the magnitude of changes in sugar environments of the honey samples, reflected in sugar phase transitions, rises with increasing infection level in bee colonies. These results indicate that fluorescence combined with MCR-ALS could be used for rapid, non-destructive and cheap screening of honey to estimate the level of infection of honey bee colonies.