Annual variation of proteins and phenols in honey of a bee society using fluorescence spectroscopy: a way to assess effects of antivarroa treatments on honey composition

Abstract

Proteins and phenols are minor, but important components of honey. Phenols originate from nectar and proteins from nectar/pollen and bees themselves. These two types of compounds are important for growth and development of bee colonies, and also for their defense capacity. Their quantity in honey depends on food accessibility and forage during the year. In this preliminary study, we aimed to see yearly dynamics of ratio of phenols and proteins in honey for a bee colony, and to observe the possible effects of extended oxalic acid antivarroa treatment on honey composition regarding proteins and phenols. Since proteins and phenols are fluorescently active, for measurement of phenol/protein ratio in honey we applied steady-state fluorescence spectroscopy as a rapid and non-destructive method. We determined the ratio of the spectral components related to these two main fluorophores in honey, proteins and phenolic compounds, as a ratiometric indicator of variability in honey samples collected in different seasons. We found that oxalic acid does not influence proteins' and phenolics' composition of honey, based on the spectral analysis. Since proteins in honey originate mainly from bees colony, this result indicates that oxalic acid did not change bee synthesis of proteins, indicating that oxalic acid, as a protective agent, is not harmful to the bees.