Quality of honeys influenced by thermal treatment

Honey producers have been heating honeys at mild temperatures below 100 °C chiefly in order to prevent post-bottling crystallization. In this study, we aimed to determine the effects of thermal treatment on the HMF content of honeydew and floral honey during the isothermal heating process at mild temperatures. Water content, formol number, total acidity, pH value and minerals were also determined in both honey types as their characteristics differ with composition, which is able to affect the rate of HMF formation. Potassium content and pH value were found as the distinguishing properties and both were greater in honeydew honey than in floral honey (p<0.01). Honeydew and floral honey samples were heated at 75, 90 and 100 °C for 15–90 min and analysed for HMF content by HPLC-RP. The Arrhenius model was used to calculate reaction rate constants and activation energies which were found to be different for each of the honey types. Heating at 90 °C for up to 90 min in floral honeys and up to 75 min in honeydew honeys did not cause a significant increase of HMF and not exceed the threshold level of 40 mg kg−1. Our results show that the excessive HMF content might be related to primitive storage conditions rather than overheating.