Authors:Monika Božiková, Peter Hlaváč, Vlasta Vozárová, Zuzana Hlaváčová, Ľubomír Kubík, Peter Kotoulek, and Ján Brindza
Knowledge of bee products’ physical properties has a decisive importance for the monitoring of their quality. Thermophysical parameters are very important properties. Thermal conductivity and thermal diffusivity of selected bee products (honey, bee pollen and perga) were measured by two different methods. For identification of thermal conductivity and thermal diffusivity transient methods were used: Hot Wire (HW) and Dynamic Plane Source (DPS) method with an instrument Isomet 2104. The principle of measuring process is based on the analysis of timetemperature relation. In the first series of measurements thermal conductivity and diffusivity at constant laboratory temperature of 20 °C were measured. The second series was focused on identification of the changes in the thermophysical parameters during temperature stabilisation in the temperature range of 5–25 °C. For samples with constant temperature standard deviations and probable errors in % were calculated. For relations of thermal parameters to temperature graphical dependencies were obtained. Two different thermophysical methods were used for improvement of data reliability and data statistics.
Authors:Anikó Kovács, Katalin Badakné Kerti, and László Somogyi
confectionary systems. Here, we investigated differences in the texture properties, the viscosity and thermalproperties of the blends. Materials and methods Commercial sugar (sucrose), stevia and xylitol were used in this study. Palm oil was purchased from
Six coloured and six non-coloured waxy rice varieties were analyzed by determining amylose, fat, and protein content, pasting, and thermal properties. Significant differences in protein content as well as pasting properties between coloured and non-coloured waxy rice were identified. It was demonstrated that protein may have a main influence on pasting and thermal properties of waxy rice. In addition, the optimal linear relationship between protein and pasting or thermal properties was found by combining RVA and DSC data using Principal component analysis (PCA). Typical indicators, which can classify coloured and non-coloured waxy rice, could be identified by Hierarchical cluster analysis (HCA). In pasting properties, trough and consistency viscosity were typical indicators; in thermal properties, enthalpy and stop temperature were typical indicators.
Authors:R. Juhász, K. Horváth, I. Dalmadi, É. Andrássy, A. Salgó, and J. Farkas
Effect of 60Co irradiation on wheat and white pepper grains were investigated in this study using Rapid Visco Analyser (RVA), near infrared reflectance spectroscopy and differential scanning calorimetry. Functional properties of wheat and white pepper were affected by irradiation indicated by a decrease in viscosity values. It was caused by changes of starch structure confirmed by the NIR spectra changes between wavelength 1560–1620 nm, which is the vibration of intermolecular hydrogen bonded OH groups in polysaccharides. The radiation used did not cause significant changes in the thermal properties. RVA proved to be useful for screening radiation induced changes in dry commodities of considerable large starch content on the basis of their rheological behaviour.
Eliasson, A. C., Silverio, J. & Tjerneld, E. (1991): Surface properties of wheat flour milling streams and rheological and thermalproperties after hydration. J. Cereal. Sci. , 13 (1), 27-39.
Surface properties of wheat flour