Application of Ultrasonic or Microwave Radiation to Delay Crystallization and Liquefy Solid Honey

Abstract Crystallization of honey is a natural process occurring during honey storage and forces beekeepers to practice the decrystallization process, which mainly concerns honey heating. The aim of this study was to examine the possible use of ultrasounds or microwave radiation to delay the crystallization of honey and to liquefy crystallized honeys while maintaining their biological activity. Lime, acacia and multifloral honeys obtained from a local apiary were used. Fresh honeys were pretreated through ultrasounds (40 kHz, for 5 and 20 min) or microwaves (800 W, 4 x 30s) in order to obtain samples U5, U20 and M, respectively. Experimental and control samples were stored for twelve months at room temperature (20±2°C) without light. Crystallized honey was liquefied through the same methods of ultrasounds (sample U5* and U20*) and microwaves (sample M*). Naturally crystallized honeys were used as the controls. For fixed (U5, U20 and M) and decrystallized (U5*, U20*, M*) honeys, the water content (refractometrically), antioxidant properties (DPPH method), total phenolics content (Folin-Ciocalteu method) and enzymatic activity (diastase, α-glucosidase, β-galactosidase and α-mannosidase) were determined. The analyzed physicochemical parameters for both fixed and liquefied honeys did not differ significantly (P>0.05) in comparison to the control honey. Moreover, the decrystallization process increased the antioxidant activity of all tested honeys. The smallest changes in honey properties to ultrasonic treatments were observed, and this method was recommended to delay the crystallization process and significantly accelerate the liquefaction time of solid honeys without compromising its quality.