Effect of moisture content on the viscosity of honey at different temperatures

Viscosity of honey was measured in two honeydew honeys (pine and fir) and four unifloral nectar honeys (thymus, orange, helianthus and cotton) at their initial moisture content as well as at 17%, 19% and 21% water content at 25, 30, 35, 40 and 45 degrees C. It was found that viscosity varied between 0.421 and 23.405 Pa s. Shear stress varied linearly with shear rate for all the samples indicating Newtonian behaviour. Shear stress was also measured at a constant shear rate as a function of time. Viscosity was time independent. Arrhenius equation was used to express the variation of viscosity with temperature. The activation energy and the constant mu(0) of the Arrhenius equation were determined as a function of moisture content from regression analysis of the experimental results. Activation energy decreased linearly as the moisture content increased varying between 70.8 and 96.3 kJ/mol. The constant mu(0) increased exponentially as the moisture content increased. (c) 2005 Elsevier Ltd. All rights reserved.