Impact of microwave heating on hydroxymethylfurfural content in Czech honeys

As far as honey is concerned, microwave oven heating finds its use especially for crystallised honey reliquefying. We focused on monitoring the changes in hydroxymethylfurfural content which is an indicator of heat damage done to honey, among others. Microwave honey heating was carried out in four degrees of microwave power levels over seven variously long time periods. In total, 22 analysed honey samples came directly from bee-keepers from the Czech Republic from the 2004 and 2006 harvests. Hydroxymethylfurfural content was determined by HPLC method using a liquid chromatograph Alliance 2695 with a PDA detector 2996. We obtained relatively interesting results: despite the honey having reached relatively high temperature levels (80-90°C) at the highest power levels and the longest time periods, there was no gradual significant increase in hydroxymethylfurfural content which could be expected at conventional heating. On the other hand, hydroxymethylfurfural content varied in the course of heating of the individual samples, which is a very interesting result. A significant role was played also by the botanic origin of the honeys because the course of the changes in hydroxymethylfurfural content due to microwave heating was not the same in all honeys analysed.