Complex Dielectric Permittivity Spectra of Rapeseed in the 20 MHz-3 GHz Frequency Range.

Rapeseed is one of the most important sources of vegetable oil worldwide. Knowledge of the dielectric properties of rapeseed may be beneficial for moisture content determination and the optimization of microwave treatment processes. The aim of this research was to examine the complex dielectric permittivity spectra of rapeseed of moisture content from 8.3% to 16.1%. The measurements were performed in the 20 MHz-3 GHz frequency range with the use of a vector network analyzer and a coaxial transmission-line cell. The real part of dielectric permittivity significantly depended on the water content of the seeds. The obtained spectra were modeled with the use of a three-pole Debye model with bulk electrical conductivity. Because the highest-frequency pole was found near the high-frequency measurement band limit, the spectra were additionally modeled with the use of an approximate ABC model with two in-band Debye poles. The determined model parameters were found to be highly dependent on the water content of the seeds. The relations between these parameters and water content were analyzed.

Physico-Chemical and Sensory Profiles of Enriched Linz Biscuits.

The aim of the present study was to determine the physico-chemical properties (dry matter content, combustion heat, electrical properties, total protein, ash, fat and crude fibre contents, selected amino acids, and trace elements), antioxidant content, and sensory profile of Linz biscuits. They were enriched by the addition of powdered carrot, nettle leaves and elderberry fruit, which is 3% of the product. For comparison of results, a control variant without the addition of these components was also prepared. The enriched biscuits showed slightly higher total ash and crude fibre contents in comparison to the control samples. Results for the antioxidant activity and total polyphenol, flavonoid, and phenolic acid contents of the enriched biscuits were higher in all observed parameters than in the control sample with the best results obtained for Linz biscuits enriched with elderberry and nettle powder. In enriched biscuits, higher contents of iron, zinc, and manganese were measured, especially in biscuits with nettle. Linz biscuits with nettle had higher combustion heat values than control samples; the other two sample types had lower values. We found that the resistance, capacitance, and relative permittivity of the enriched biscuits decreased with frequency according to the power regression function. On the contrary, the conductivity increased with an increasing frequency. Electrical properties were mainly influenced by the water content but also by added components.