Modeling the effect of temperature and relative humidity on physicochemical properties of honey Laleh Mehryar a , Mohsen Esmaiili a , Ali Hassanzadeh b a Department of Food Science and Technology, University of Urmia, Urmia, Iran (laleh.mehryar@gmail.com ) & (m.esmaiili@urmia.ac.ir ) b Department of Chemistry, University of Urmia, Urmia, Iran (a.hassanzadeh@urmia.ac.ir) ABSTRACT Several physico-chemical, thermal and rheological characteristics of six Iranian honey samples from various floral sources were investigated. The studied parameters were: moisture content, water activity (a w ), water insoluble solids, diastase activity, pH, free acidity, total sugar content, reducing sugar, fructose to glucose ratio, sucrose content, ash, fat, total nitrogen content, HMF, density, specific weight, color with hunter parameters (L, a and b), electrical conductivity, glass transition temperature (T g ), viscosity, stickiness and equilibrium moisture content. In order to have a precise evaluation of honey samples, some of its physical properties such as density and viscosity were investigated at three temperature levels. To study the temperature effect on viscosity Arrhenius, VTF and power law models were considered. The evaluations of the models were done by R 2 , P%,  2 and RMSE indices. There were some relationships with high coefficient of determination between physical and chemical properties. At the studied shear rate (0.04-0.63 s -1 ), all of the samples showed non-Newtonian (pseudoplastic and dilatant) behavior. Among three applied models, samples 1, 2 and 3 showed a well accordance with Arrhenius and samples 4, 5 and 6 with VTF models. Equilibrium moisture content (EMC) of the samples was increased by increasing water activity but the inversion effect has appeared at a constant water activity (>0.5) among different temperatures of the samples. Keywords: Honey; physicochemical properties; glass transition; stickiness 1. INTRODUCTION Among most of the natural foods, honey still has its own valuable place for long centuries. This unique nutritional and prophylactic-medicinal substance is a sweet, viscous and aromatic fluid elaborated by the honeybee from the nectar of plants or honeydew. Considering the various climatic conditions present in Iran expecting many different kinds of honeys from sensory and physicochemical aspects is not amazing. In order to give an authoritative statistic of the country’s production, the 11th rank was attributed to it by the Food and Agricultural Organization (FAO) in the year 2008 and surely it has improved since then [1]. According to ISNA by producing over 14 thousand tons of honey, West Azerbaijan province (located in North West of Iran) has the 1st rank in the total production of the country [2]. Physical and rheological properties of honey are very useful in its processing, handling and storage [3]. Most of the physicochemical properties of honey such as viscosity, hydroscopicity, and granulation are due to its composition that is sugars and moisture content [4]. The composition of honey depends highly on the type of flowers utilized by the bee as well as climatic conditions [5]. The Arrhenius, VTF and Power law models are useful for temperature dependence of viscosity [3, 6]. The honey viscosity depends on the honey water content, temperature and chemical constitution [7, 8]. Most honey varieties show Newtonian behavior [3-4, 8-10] while there are some which show non-Newtonian behavior [7-8, 11-12]. Materials with amorphous or partially amorphous structure undergo a transition from a glassy solid state to a rubbery viscous state at a material-specific temperature range, which is called the glass transition temperature (T g ). Measuring the Glass Transition Temperature of honeys by the use of DSC was done by most scientists in literature [3-4, 6, 13-16]. Moisture sorption/desorption isotherms are useful in food dehydration, storage and packaging. Because of the complex food composition, experimental measurements are necessary for prediction of the isotherms.