dynamic viscosity, fluidity, kinematic viscosity, storing time, temperature, thermal conductivity, thermal diffusivity, volume specific heat, whisky
Abstract
Temperature and storing time can be included between the most significant parameters that influence physical properties of food. This article deals with selected rheologic and thermophysical properties of alcohol drink whisky. Our research was oriented on measuring of rheologic and thermophysical characteristics of whisky. There were measured two types of whisky – Grant’s and Jim Beam from two different producers, both samples had 40 % of alcohol content. During the experiments were analyzed rheologic parameters as: dynamic viscosity, kinematic viscosity and fluidity and thermophysical parameters as: thermal conductivity, thermal diffusivity and volume specific heat. Selected parameters were measured in temperature range (-5 – 27) °C. Measurements were done on whisky samples in different days during the storage. Measuring of dynamic viscosity was performed by digital rotational viscometer Anton Paar (DV-3P). Principle of measuring is based on dependency of sample resistance against the probe rotation. Density of whisky samples was determined by pycnometric method. Average density at given temperature along with dynamic viscosity value was used at calculation of kinematic viscosity and fluidity was also determined. Measuring of thermophysical parameters was performed by instrument Isomet 2104. Measurement by Isomet is based on analysis of the temperature response of the measured sample to heat flow impulses. Relations of rheologic and thermophysical parameters to the temperature were made and influence of storing time was discussed. From obtained results is clear that dynamic and kinematic viscosity is decreasing exponentially with temperature and fluidity has increasing exponential progress. We found out that both whisky samples had at the beginning and after one week of storage very similar values of rheologic parameters. Very small difference in rheologic parameters of whisky samples was found after two weeks of storing. Values of dynamic and kinematic viscosity were a bit higher and values of fluidity were a bit smaller after storing, that can be caused by loosening of the water during storage. Thermophysical parameters are increasing linearly with temperature for both whisky samples. Higher values of thermophysical parameters were in all cases obtained for whisky Grant’s.
