Study of vacuum and freeze drying of bee honey
Nebojša Nedić, Milan Gojak, Ivan Zlatanović, Nedžad Rudonja, Kristina B. Lazarević, Milan Dražić, Kosta Gligorević, Miloš Pajić
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.