| Summary: | 碩士 === 大葉大學 === 生物產業科技學系 === 96 === Water mobility is one of the most important topics in food area. The object of this research is: using ohmic heating to determine food water mobility affected by voltage, frequency and wave form. Fresh carrot and potato cylinders (2cm in height, 2.5cm in diameter) were heated ohmically to 50℃ or 80℃ using two voltage (60 and 120 V/cm), three frequencies (4, 60 and 1000 Hz) and two wave forms (square and sine wave). Physical properties of treated samples, such as electrical conductivity, porosity, heating time, temperature, and water mobility were measured. Besides, scanning electronic microscope (SEM) will be conducted. Data showed that samples treated by sine wave, 4 Hz, and 60 V/cm resulted in increasing electrical conductivity, from 0.0049 S/m (control) to 0.1851 S/m for carrot and from 0.0058 S/m (control) to 0.1162 S/m for carrot; whereas porosity data showed increases of 0.3726 (control) to 0.5823 for carrot, and 0.4472 (control) to 0.5654 for potato. The increasing electrical conductivity could be due to structure collapse, and high porosity. The scanning electronic microscope (SEM) will be conducted. Otherwise, samples treated by square wave, 1000 Hz resulted in increasing water mobility, but electrical conductivity and porosity increased mildly. We conjectured that there might be other considerations affected water mobility.
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