Honey after crystallization is called set honey and is a two-phase structure, semisolid, which substantially varies in its properties from the liquid state-strained honey. The resulting solid phase is a glucose monohydrate, which has various geometrical forms in crystallization. Melezitose can also undergo crystallization in honeys. The crystallization process results directly from the chemical composition, as in almost all types of honey glucose are present in its supersaturated state. Due to this, most of the obtained types of honey undergo crystallization when in storage. īee honey is a concentrated aqueous solution of sugars. The parameters, which significantly influence the dynamic viscosity of the analysed product, are temperature and water content. It needs to be stressed, however, that such reports are with regard to honey in its liquid state also known as strained honey. A few publications hint at the existence of a clear thixotropic effect, although it is only seen in certain types of honey such as heather honey or the Manuka honey from New Zealand. In multiple published reports on the rheological properties of honey, there is a common observation that it is in fact a Newtonian fluid. Viscosity is additionally one of the parameters of quality assessment of the product. The rheological properties of honey are analysed mainly within the aspect of fulfilling the basic production processes such as hydraulic transport, mixing, heating or batching. Rheology is tasked with the description of these properties. They demonstrate partially viscous, elastic and plastic properties.
Generally, non-Newtonian fluids are divided into rheologically stable, rheologically unstable and viscoelastic. All fluids, which do not fulfil Newton’s law, are called non-Newtonian fluids. The η parameter in the equation above stands for dynamic viscosity. It was shown that the research method influences the obtained results of rheological studies. Results of measurements under forced oscillation conditions are included and compared with results of rotational measurements.
Among other items, the dependency of equilibrium stress on shear rate, apparent viscosity on crystalline phase content, hysteresis loops as evidence that honey in its crystallized form is a rheologically unstable fluid. Results of characteristic experiments are presented, obtained during the shearing of crystallized suspension, that is, crystallized honey. In the case of crystallized honey, the rheological properties were linked to morphological features and crystalline phase content. The basic mathematical models are shown, which describe the viscosity of honey in its liquid form depending on temperature and water content. The research methods used in both cases are characterized. The rheological properties of honey are discussed separately for liquid and crystallized honey.
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