Ultrasound-assisted liquefaction of rosemary honey: Influence on rheology and crystal content

Crystallization of honey is a common process of the honey industry. Liquid honey is preferred by most of the consumers and by food companies for ease of handling. A better method compared to expensive and time-consuming heating is desirable to accelerate the liquefaction and retard the crystallization process in honey. In this work, samples of crystallized honey were liquefied by an ultrasonic bath of 40 kHz at temperatures of 40–60 °C for 20, 40 and 60 min. Then, the rheological properties and crystal content were analyzed and compared to only heat-treated samples. Results show that an ultrasound treatment speeds up the liquefaction of honey especially at temperatures below 50 °C. Lower temperatures preserve the honey’s quality and save the energy consumption. In addition, ultrasound-treated samples are clearer and more transparent than only heat-treated honey samples. The amount and size of the crystals were also smallest in the ultrasound treated samples.

► High-power low-frequency ultrasounds at 40 kHz speed up the liquefaction of honey in a temperature range of 40–50 °C.
► The activation energy of the ultrasound-treated samples is higher than that of only heat-treated samples.
► Ultrasound-treated samples are clearer, more transparent and contain smaller crystals than only heat-treated samples.
► Rosemary honey presents a Newtonian behavior.