Thixotropic Behavior of Honey from Eucalyptus spp

Honey is a solution with high viscosity and most types of honey exhibit Newtonian behavior. However, some types show non-Newtonian features (thixotropy or dilatancy), which exerts influence on processing of the honey. The aim of this study was to evaluate the rheological properties of honey from Eucalyptus spp. The investigated samples of eucalypt honey originating from Italy or Australia were analyzed by the following methods: melissopalynological analysis, color on the Pfund scale, optical activity, water content and electrolytic conductivity. Rheological tests were carried out on a highly accurate device. The dependence of apparent viscosity on temperature and time was measured, and hysteresis loop tests were run. The dependence of shear rate on shear stress was described in accordance with the Herschel-Bulkley mathematical model. The rheological tests revealed the following: all samples exhibited non-Newtonian behavior and all were determined as thixotropic fluids. These results are discussed in relation to previous findings on the dilatant behavior of eucalypt honey. Practical Applications Knowledge of rheological properties of foodstuff is important for handling, processing and storing. The description of flow properties can indirectly offer information about the structure of the tested liquid. Most honeys behave as Newtonian fluids. However, there are exceptions such as heather or manuka honey. Eucalypt honey is also among these exceptions. Studies dealing with rheological properties of eucalypt honey are more than 60-years old. This study focused on rheological behavior of this type of honey and revised current knowledge.