Study of vacuum and freeze drying of bee honey

Abstract

The aim of this research is to study the drying kinetics of vacuum-dried and freeze-dried bee honey produced from two different varieties: Sunflower honey (Helianthus Annuus L.) and Acacia honey (Robinia pseudo acacia L.). Vacuum drying treatments were carried out with the honey samples’ initial temperatures of +25 °C, –20 °C, and –40 °C. Water content, total soluble solids, as well as the water activity of fresh and dried honey samples were determined. Freeze-drying of bee honey with initial sample temperature of –40°C has resulted in shorter drying time (7-9 hours), moisture content (10%-12%), water activity (0.405-0.427 aW) and effective moisture diffusivity coefficient (8.26·10–7-9.51·10-7 m2/s). The high-performance liquid chromatography method was used when analyzing the impact that drying pre-treatments had on honey quality. The application of pre-treatments has led to an increase in hydroxy-methyl-furfural by 39-71%, and a decrease in diastase activity by 17-36%, all compared to fresh honey samples. The solutions of Verma model proved to be the best fit with the experimental results.