The influence of cooking procedures on doxycycline concentration in contaminated eggs.

Doxycycline (DC) is forbidden compound in laying hens. Most information about drug residues in eggs concern their concentrations in raw matrix and the data about the influence of cooking on antibiotics residues in eggs are limited. Thus, the residues concentration of DC in eggs after different cooking methods was investigated. Analyses of DC were assayed by liquid chromatography - tandem mass spectrometry method. The stability of DC in eggs were depended upon the type and time of cooking procedure. By microwaving DC was reduced most effective with concentrations decreased by 53% and 50.3% after 4min of microwaving without cover and microwaving with cover, respectively. In fried eggs, DC was reduced by 39.8% in 6min. By the boiling cooking, the smallest reduction was observed with the concentration decreased by 29.8% after 8min. The obtained results show that ordinary cooking does not eliminate the all DC residues present in eggs.