The first microwave measurement techniques uses an open ended coaxial probe with a purposely built sample holder to measure the dielectric properties of potato products from 500 MHz to 1 GHz. The second system utilises a waveguide cell with a purposely built sample holder to characterise potato products from 2.4 to 3.5 GHz. Common British varieties of raw potatoes such as Estima, King Edward and Maris Piper are used in this study. The two microwave measurement techniques are also used to measure the dielectric properties of potato products at elevated temperatures for these frequency ranges. Both measurement techniques are also used to study the effect of storage temperature on the dielectric properties of Saturna raw potato. For this part of the study, it is concluded that the microwave measurement techniques are unable to discriminate between potatoes that had a storage history of different temperature profiles. On the other hand, waveguide cells and open ended coaxial probes are able to measure the dielectric properties of raw potato, partial cooked fried potato and fried potato at the 500 MHz to 1 GHz and 2.4 GHz to 3.5 GHz frequency range. The measurement results show that both dielectric constant and loss values of fried potatoes decreased with frying time, due to the reduced moisture content during the frying process. Furthermore, the dielectric loss behaviour of raw and fried potatoes is dominated by the effect of the ionic conductivity at frequencies lower than 1 GHz. An apparatus has been designed and built in order to measure the dielectric properties of potato for both frequency ranges as a function of temperature. In the subsequent measurements it is found that the dielectric properties of potato products at elevated temperatures also depend on frequency and moisture content. For high moisture content potato (~> 70 %), at 2.45 GHz both the dielectric constant and loss are found to decrease with temperature, whereas at 915 MHz the dielectric constant decreases but the loss increases for the moisture content above 30%. For the intermediate moisture content (10%<MC<70%), all dielectric properties increase with temperature at the microwave heating frequencies 2.45GHz, whereas at 915 MHz all the dielectric properties increase with temperature for the moisture content range 10% to 30%. The increase in dielectric properties with temperature is small and marginal for fried potatoes with low moisture content (< 10 %). It is therefore apparent that moisture content is the primary factor in detecting the complex permittivity of potato products.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:518884 |
| Date | January 2010 |
| Creators | Mohamad Noh, Badaruzzaman Bin |
| Contributors | Gibson, Andrew |
| Publisher | University of Manchester |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
| Source | https://www.research.manchester.ac.uk/portal/en/theses/application-of-microwave-sensors-to-potato-products(446a6ec2-13b0-4392-920a-160bc66e9912).html |
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