Ultrasound-assisted liquefaction of honey

Résumé

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. Honey is commonly heated during pasteurization in order to liquefy it and inhibit any microbial growth. However, heating can degrade the main quality parameters of honey. A better method compared to expensive and time-consuming heating is desirable to pasteurize, accelerate the liquefaction and retard the crystallization process in honey. The present thesis documents the work done at investigating the effect of the ultrasounds (US) in honey liquefaction, quality alteration and honey decontamination. Firstly, in Chapter 1, the effect of different combinations of US treatment (power, temperature and duration) on honey liquefaction were evaluated by studying the rheological properties of honey; viscosity behaviour, crystal content, tendency to re-crystallization and thermal properties. Secondly, in Chapter 2, the effects of US on the hydroxymethylfurfural concentration and diastase activities in honey were determined by chemical analysis and compared with that for standard heat-treated honey samples. Thirdly, in Chapter 3, US treatment was investigated for honey decontamination. In addition, the in vitro antimicrobial and antifungal activities of ultrasonicated honey against several types of microorganisms were evaluated. The results obtained in this research point to a successful application of the ultrasound technology for the liquefaction of honey, as it speeds up its liquefaction, do not degrade the quality and the intrinsic biological activity of honey was neither affected.